From: Brian Lo Newsgroups: rec.gardens Subject: FAQ: Onions Date: Wed, 1 Mar 1995 14:55:54 -0800 ONIONS, DRY BULB, WEST OF THE CASCADES Allium cepa See separate files: Onions, Dry Bulb, East of the Cascades (ONIONB-E), or: Onions for Dehydration (ONDHY), or: Onions - pearl, sets and boilers (ONPRL), or: Green Bunching Onions (ONGRN). Dry bulb onion in the Pacific Northwest may be classified into two distinct catagories those that are grown on muck soils, and those grown on mineral soil. By far, most are produced on mineral soils. Mineral soil onions are produced in two different regions, west of the Cascade Mountains, and east, notably in the Treasure Valley and the Columbia Basin. On both sides of the Cascades, mineral soil onions may be spring-planted or fall- planted for over-winter production. Over-winter production has been well established in the Milton-Freewater area of Oregon and the Walla Walla area in Washington. Over-winter production west of the Cascade Mountains is relative- ly new, and restricted to the Willamette Valley. Over-winter onion production is more risky, but allows harvest of onions in late May and June when onion prices are historically the highest of the year. Bulb onion varieties are classified according to day length. All bulb onions grown in the Pacific Northwest are classified as long-day varieties requiring 14 or more hours of day length before bulbing occurs. Technically, all onions are "long-day" plants, in that bulbing begins as day length inc- reases. Short-day varieties are those requiring only 10 to 12 hours of day length for bulbing to occur. These are grown in southern states generally below the 35 th. parallel, and are not suitable for bulb production in the northwest, except as pearl or boiler varieties, or for over-winter production. Temperatures and light intensity and quality (red:far red) can modify onion bulbing response. High temperatures and bright days can "compensate" for some day length, causing onions to bulb sooner than they would otherwise. Overcast, cool temperatures, delay bulbing. Time of bulbing is an important factor in determining onion bulb size. Early bulbing contributes to small bulb size, with delayed bulbing resulting in larger size. Uniformity of maturity (rate of tops-down) is very important in bulb size uniformity and storage quality. Tops-down in hybrid varieties tends to occur over a period of only a day or two, with close to 100% of the tops falling. Non-uniform varieties may have tops falling over a period of several weeks with a percentage of the tops not falling at harvest. In such variet- ies, bulbs with early tops-down contribute to incidence of bald onions at harvest, while those whose tops resist falling do not cure properly, contrib- uting to decay in storage. Cool temperatures, poor stands and late plantings predispose varieties to bull necks, a trait that contributes to poor storability. This is espe- cially true of late, varieties that may have poor bulbing uniformity qualities (sometimes more prevalent in non-hybrids). Selecting the correct variety for your production area and understanding the climatic and other environmental factors that affect its performance is extremely important. VARIETIES Western Oregon (spring seeded): Muck soils; spring seeded, yellow: Simcoe, Sentenial, Capable, Cuprum, Topaz, Taurus, Australian Brown, Spartan Banner 80, Spartan Sleeper, Columbia, Yellow Globe Danvers strains. Western Oregon, mineral soils; spring seeded, yellow: Early sales-yellow: Progress, Rocket, Granada, Simcoe, Aries, Taurus, Pronto, Early Pak, Yula. Storage-yellow: Rocket, Granada, Simcoe, Aries, Taurus, Spartan Ban- ner, Sentinel, Capable, Autumn Splendour, Improved Autumn Spice, Canada Maple, Super Sleeper, Spartan Sleeper, Sentinal, Australian Brown, Sweet Sandwich, Golden Cascade. For trial: Candy, Pinnacle, First Edition (long storage). Red: Tango, Carmen, Benny's Red. Torpedo (long, spindle-shape, sweet). For trial: Fuego. White (white types are only marginally adapted to western Oregon): Blanco Duro, White Delight. Medford area: Yellow: Grenada, Vega, Sweet Amber, Bravado, Brahma, Valdez, Magnum. White: Avalanche, Blanco Duro, Glacier. Red: Carmen, Tango, Bennies Red. Torpedo (long, spindle-shaped, sweet). Fall seeded over-wintering onions - Yellow: Top Keeper, Hi Keeper, Buffalo, Keep Well, Hi Ball, Bison, Senshyu Yellow, Imai Yellow, Walla Walla (a number of Walla Walla onion strains exist: Early and late French, Arbini, Locati and others; none are hybrids). Red: Red Cross (a large, "Bermuda" or flat onion), Kurenai. These onions are planted in mid August to mid September and harvested in late June-July Dehydration types: See seperate file. Pearl or cocktail onions; boiler onions and onion sets: See seperate file. SEED COMPANIES Abbott & Cobb Inc. POB F307, Feasterville, PA 19047 Asgrow Seed Company, POB 5038, Salinas CA 93915 American Takii Inc., 301 Natividad Rd. Salinas, CA 93906 Bejo Seeds, 1323 E. Fir St. Mt. Vernon WA 98273 Champion Seed Co. 529 Mercury Lane, Brea, CA 92621-4894 714/529-0702 Crookham Co. Caldwell, ID 83606 Dakota Seed International Inc. POB 5467, Saginaw, MI 48603 Ferry-Morse Seed Co. POB 4938, 555 Codoni Ave. Modesto, CA 95352 Harris Moran Seed Co. 3670 Buffalo Rd. Rochester, NY 14624 Petoseed Co. Inc. POB 4206, Saticoy, CA 93303 Rio Colorado Seeds, Inc. 4701 Gila Ridge Road, Yuma AZ 85365 Scottseed. 4876 N. Road H. Vale OR 97918 503/473-3246 Shamrock Seed Co., Inc. POB 4443 Salinas, CA 93912 Sluis & Groot of America Inc. 124 Griffin Street, Salinas, CA 93901 Stokes Seeds Inc. POB 548, Buffalo, NY 14240 Sunseeds, 2320 Technology Pkwy. Hollister, CA 95023 W. Osborne Seed Co. Int'l. 1679 Highway 99 South, Mount Vernon, WA 98273 Zenner Bros. Seed Co., Inc. 1311 S.E. Gideon St. Portland, OR 97202 SOIL TEMPERATURE The optimum temperature range for germination is 48 to 90 F. March and April plantings are most common in western and central Oregon. SOILS In western Oregon, onions are grown on peat soils or silt loams and sandy loams. Overwintered crops must have soils with good internal drainage. SEEDING AND TRANSPLANTING In western Oregon planting is from approximately the 20th. of March through the first week of May. Onion seed numbers approximately 9,500 per ounce. Most onions are direct seeded. A few acres of overwintering Walla Walla Sweet onions are transplanted in northern Umatilla County. Some later varieties of sweet Spanish onion are transplanted in the Willamette Valley. About 120,000 to 140,000 transplants are needed to plant one acre (when planted 3-4 inches apart in rows 15 - 24 inches apart). Only garden onions are grown from sets. When sets are used, about 800 lbs of 15/16 inch or smaller diameter sets, are needed per acre. The depth of transplant or set placement has an effect on onion shape (see section on seeding below). Precision Seeding This method of placing individual seeds at a predetermined spacing within a row produces a crop of more uniform size, less culls and higher yield of the desired size grade. Present recommendations are to use coated seed and to seed two lines 3 in. apart per row with 6-12 seeds per ft. of row (depend- ing on variety), and rows 10-12 inches apart. Stanhay, Beck, or Graymore planters are used with coated seed. New vertical plate vacuum planters such as the Gaspardo or Stanhay also may be used with uncoated seed. Spring Seeding: Onions may be seeded as soon as the land can be made ready, but mid- April is considered ideal. If seeded too late, bulbs will be small since bulbing will begin before adequate growth occurs. Seeding should be completed by May 5 in Western Oregon. Approximately 2-3 lbs. of seed are required per acre when using a Planet Junior planter with 2 to 4 inch scatter shoe. Planters should be set to drop 5-10 seeds per foot of row (depending on the variety and size of onion to be grown), 3/4 to 1 inch deep. Depth of seeding has an effect on bulb shape since the onion stem plate (the base of the onion bulb) forms at the point where the seed germinates. Shallow planting results in flatter bulbs, while deeper seed placement results in taller, and sometimes top-shaped bulbs. Spacing between rows is usually 10-12 inches apart in Western Oregon, where sets of 4 or 5 rows are used between wheel spacings. Fall Seeding: Over-wintered onions are seeded in August to mid September. The earlier seeding dates are preferred with the more bolting resistant varieties. Plant spacings and configurations are the same as described above, except that final spacings should be 3-4 plants per foot of row to obtain the jumbo sizes desi- red in these types of onions. Over-wintered onions are grown for their mild- ness and succulent texture which will not stand crowding. Over crowding will cause these onions to become badly misshapen and flat-sided. It has been observed that temperatures under 20 F. during the winter months may lead to thickened and elongated necks at harvest that cure poorly. Some varieties (Walla Walla Sweet) are more susceptible to this problem than other varieties recommended. Transplant Production: Sow 2-3 lb. of seed to obtain enough plants for each acre to be trans- planted. One acre of seed-bed can produce enough transplants for 12 acres of onions. Seed is drilled to a depth of l in. or slightly less. Seed may be drilled with a wide shoe attachment which scatters the seed over a 4 in. band in rows with 16 in. centers. Light sprinkler irrigation following seeding will often be necessary to obtain a satisfactory stand. Loosen plants before pulling, and tie in bundles of 100 to 200. If being moved any distance, or if transplanting will be delayed, store at 32- 36 F with relative humidity of 90%. Immediately before planting, trim the plants to leave l/2 in. of the original root and 4 in. of the green top. Set in rows 12-16 in. apart, with 3-4 in. between plants. FERTILIZER The following guides for western Oregon onion fertility management have been quoted from OSU Fertilizer Guide 67 (for western Oregon muck soils) and are based on muck soil and mineral soil research conducted by faculty of the Soils and Horticulture Departments of Oregon State University. Western Oregon Mineral Soils: Spring seeded onions: A soil test is the most accurate guide to fertilizer requirements. Good management practices are essential if optimum fertilizer responses are to be realized. These practices include use of recommended varieties, selection of adapted soils, weed control, disease and insect control, good seed bed preparation, proper seeding methods, and timely harvest. Because of the influence of soil type, climatic conditions, and other cultural practices, crop responses from fertilizer may not always by accurate- ly predicted. Soil test results, field experience, and knowledge of specific crop requirements help determine the nutrients needed and the rate of applica- tion. Fertilizer application for onions should insure adequate levels of all nutrients. Optimum fertilization is essential for top quality and yields. Fertilizer suggestions are based on a 12"-14" row spacing. Recommended soil sampling procedures should be followed in order to estimate fertilizer needs. NITROGEN (N): N rate of 20-40 lbs/A should be broadcast and worked into the seedbed before planting, using fertilizers such as ammonium sulfate, 16-20-0 or a mixed fertilizer containing sulfate sulfur. Note: When mild-flavored onions are desired, reduce sulfur applications to the minimum recommended for proper plant growth since sulfur applications have been shown to increase onion pungency (see sections on "sulfur" below). An additional 100-120 lbs/a should be applied during the growing season when onions are 6-8" tall. Fall seeded overwintering onions: Use only 30-50 lbs of N/A at time of planting. Apply all additional N in the spring in March, April and May. Be careful to minimize growth in the fall (by limiting N and water applica- tions) so that plants go into the winter about 1/4 inch in diameter otherwise excessive bolting will occur in the spring. Sidedressed nitrogen applications or nitrogen applied in irrigation water can be an effective means of providing supplemental nitrogen to the crop during the season. DO NOT use aqua or anhydrous ammonia in sprinkler irriga- tion. Nitrogen liquid fertilizer formulations having herbicidal effects: AN-20, Ammonium Thiosulfate and mixtures of these two materials can be used in a number of crops. Monocarbamide Dihydrogensulfate (Monourea sulfuric acid) is used in Alliums such as onion, shallots, leeks and garlic. The amount of nitrogen per gallon of material, the rate at which it is applied, and the phyto-toxicity of the material determines what crops these can be used on. Monocarbamide Dihydrogensulfate (Monourea sulfuric acid) is also sold as an herbicide under different trade names (see below). ALWAYS FOLLOW THE LABEL WHEN USING THIS MATERIAL AS AN HERBICIDE. All of these materials, when applied at the proper time and manner have the added benefit of ancillary control of many small (less than 3 inches) broadleaf weeds such as groundsell, pineapple weed, shepherdspurse, mallow, pigweed, hairy nightshade chickweed and many others. Poor, or no control is obtained on lambs quarters, purslane, henbit, black nightshade, knotweed, sow thistle, malva goosefoot and grasses. When using these nitrogen sources in foliar applications, follow cau- tions listed. Severe crop injury may occur if cautions are not observed. General cautions that apply to nitrogen liquid fertilizer formulations are: * Apply to onions only after the first true leaf is as tall as the flag leaf and before onions are 8 inches tall. * Do not apply within 4 days of a period of cool, cloudy or rainy weather, or if free water is present on the leaves. * Discontinue application if spray droplets do not roll off or "bead- up" on the leaves. This indicates a deficiency of adequate waxy cuticle, and may be a temporary condition due to rapid growth, cloudy or rainy weather, or more seriously, the lack of adaptability of the variety. * Do not apply within 4 days after a foliar pesticide has been applied, or with any wetting agent. * Use large nozzles to minimize misting and possible injury to the crop growing point. AN-20 fertilizer formulation: This is a manufactured 20-0-0 formulation (containing 20% N) that may be applied at 50 to 70 gallons of product per acre as a foliar spray. This formulation weighs 10.55 lbs per gallon and contains 2.11 lbs N/gallon of product and would provide approximately 100 to 140 lbs N/acre (but some N is lost through volatilization). Do not irrigate for 48 hours after application, but irrigate then to move the fertilizer into the root zone. When this treatment is used, subsequent nitrogen side dressings should be reduced by a portion of the amount of N applied in the treatment. Note: Mixtures of An-20 and Ammonium thiosulfate (usually 1:1) can be made which will reduce the amount of nitrogen applied, provide some sulfur (if AN-20 only would have been applied, and reducing the sulfur if only Ammonium thiosulfate were to be used), and be as effective as either material alone. Application rates are still held at 50 to 70 gallons of the mixture per acre. Note: This formulation is different from a solution that could be prepared by dissolving ammonium nitrate in water. Such a solution would not have the same concentration or herbicidal effect. Also, To prevent crop injury, follow the cautions listed above. ***** Ammonium thiosulfate: This is a manufactured 12-0-0-26 formulation (containing 12% N and 26% sulfur) and weighs 9.33 lbs per gallon. It may be applied at 50 to 70 gallons of product per acre as a foliar spray. This solution contains 1.12 lbs nitrogen and 2.4 lbs sulfur per gallon of product and would provide approxi- mately 55 to 75 lbs N/acre (some N may be lost through volatilization). At the application gallonage mentioned, about 150 to 168 lbs of S are also applied. Do not irrigate for 48 hours after application, but irrigate then to move the fertilizer into the root zone. When this treatment is used, subsequent nitrogen side dressings should be reduced by a portion of the amount of N applied in the treatment. Note: Mixtures of An-20 and Ammonium thiosulfate (usually 1:1) can be made which will reduce the amount of nitrogen applied, provide some sulfur (if AN-20 only would have been applied, and reducing the sulfur if only Ammonium thiosulfate were to be used), and be as effective as either material alone. Application rates are still held at 50 to 70 gallons of the mixture per acre. Also, To prevent crop injury, follow the cautions listed above. ***** Monocarbamide Dihydrogensulfate (Monourea sulfuric acid) 15-0-0-16 (n-pHuric or ENQUIK): This product is recommended for use on onions (bulb and green), shal- lots, leeks and garlic only. This product is also registered as an herbicide to be applied at 10 to 30 gallons of product per acre as a foliar spray. FOLLOW THE LABEL INST- RUCTIONS WHEN USING IT AS A NITROGEN SOURCE OR AS AN HERBICIDE. It weighs 12.65 lb/gallon and contains 1.9 lbs of nitrogen and 2.0 lbs sulfur per gallon of product. It is most generally used at about 15 to 20 gallons per acre pro- viding approximately 28 to 38 lbs of N per acre (but some N is lost through volatilization). Apply in sufficient water to get good foliar coverage (approximately 1:1 dilution). Do not irrigate for 48 hours after application, but irrigate then to move the fertilizer into the root zone. When this treatment is used, subsequent nitrogen side dressings should be reduced by a portion of the amount of N applied in the treatment. CAUTION: This solution is corrosive, and can injure skin and damage spray equipment. Use proper safety precautions and suitable spray equipment (stainless steel). Also, To prevent crop injury, follow the cautions listed above, and FOLLOW ALL LABEL INSTRUCTIONS. ***** PHOSPHORUS (P): Phosphorus is essential for vigorous early growth of seedlings. All phosphorus should be applied at planting, regardless of whether spring- seeding or fall seeding. P should be banded at planting 2" to the side and below the seed. If the OSU soil test Apply this amount of for P reads (ppm): phosphate (P2 O5) (lbs/A): 0-40 170-200 40-100 140-170 over 100 100-140 POTASSIUM (K): All K should be applied and worked into the seedbed before planting. Onions require medium levels of available soil potassium. The K soil test is based on K present in the surface soil (0-12"). If the OSU soil test Apply this amount of for K reads (ppm): potash (k2 o) (lbs/A) 0-100 150-200 100-200 100-150 200-350 50-100 Over 350 0-50 MAGNESIUM (Mg): When the soil test value is below 1.0 meq Mg/100g, broadcast 20 to 25 lb Mg/A and work into the seedbed before planting. If deficiency symptoms appear, spray with 10 lb Epsom salts in 100 gal water/A. Mg can also be supplied in dolomite, which is a liming material and reduces soil acidity to about the same degree as ground limestone. Dolomite should be mixed into the seed bed in the fall. BORON (B): No consistent responses of onions to the application of B have been observed in western Oregon. Where the soil test for B is below 0.25 ppm growers may wish to make a trial application of 2 lb B/A. Too much B ferti- lizer can be highly toxic and suggested rates of B application should not be exceeded. B should be evenly distributed over the field and not banded. ZINC (Zn): The application of Zn has increased the yield of onions where soils have been deficient. When the soil test for Zn is below 2 ppm broadcast 10 lb Zn/A before planting or include 3-4 lb Zn/A in the fertilizer band. A broadcast application of 10 lb Zn/A should supply Zn needs for 2 or 3 years. OTHER NUTRIENTS: Responses of onions to nutrients other than those discussed in this guide have not been observed in western Oregon. LIME: Onions are classified as being "very sensitive to soil acidity" when grown on mineral soils. Lime applications should be considered when mineral soil pH is 6.0 or below. Lime should be mixed into the soil in the fall for best results. Keep mineral soil pH between 6.0 and 6.8. For acid soils low in magnesium (Mg) (less than 1.0 meq Mg/100 g of soil) 1 Ton/A of dolomite lime can be used as a Mg source. Dolomite and ground limestone have about the same ability to neutralize soil acidity. Western Oregon Muck Soils: The following recommendations for muck soil onion fertility have been quoted from OSU Fertilizer Guide 67 based on research conducted by faculty of the Soils and Horticulture Departments of Oregon State University . A soil test is the most accurate guide to fertilizer requirements. Good management practices are essential if optimum fertilizer responses are to be realized. These practices include use of recommended varieties, selection of adapted soils, weed control, disease and insect control, good seed bed preparation, proper seeding methods, and timely harvest. Because of the influence of soil type, climatic conditions, and other cultural practices, crop responses from fertilizer may not always by accurate- ly predicted. Soil test results, field experience, and knowledge of specific crop requirements help determine the nutrients needed and the rate of applica- tion. The fertilizer application for onions should insure adequate levels of all nutrients. Optimum fertilization is essential for top quality and yields. Fertilizer suggestions are based on a 12"-14" row spacing. Recommended soil sampling procedures should be followed in order to estimate fertilizer needs. See also the comments in the section "western Oregon mineral soils - nitrogen" regarding "liquid nitrogen fertilizer solutions having herbicidal effects" as you consider nitrogen applications on western Oregon muck soils. NITROGEN (N): An N rate of 20-40 lbs/A each should be broadcast and worked into the seedbed before planting, using fertilizers such as ammonium sulfate, 16-20-0 or a mixed fertilizer containing sulfate sulfur. Caution, when mild- flavored 2onions are desired, reduce sulfur applications to the minimum recommended for proper plant growth since sulfur applications have been shown to increase onion pungency (see section on "sulfur" below). An additional 20-60 lbs/acre of nitrogen should be applied during the growing season when onions are 6-8" tall. Refer also to the section above "western Oregon mineral soils - nitro- gen" regarding "liquid nitrogen fertilizer solutions having herbicidal effects" as you consider nitrogen fertilization. PHOSPHORUS (P): P is essential for vigorous early growth of seedlings. P should be banded at planting 2" to the side and below the seed. If the OSU soil test Apply this amount of for P reads (ppm): phosphate (P2 O5) (lbs/A): 0-40 120-150 40-100 80-120 over 100 60-80 POTASSIUM (K): K should be applied and worked into the seedbed before planting. Onions require medium levels of available soil potassium. The K soil test is based on K present in the surface soil (0-12"). If the OSU soil test Apply this amount of for K reads (ppm): potash (k2 O) (lbs/A): 0-100 150-200 100-200 100-150 200-350 50-100 Over 350 0-50 MAGNESIUM (Mg): When the soil test value is below 1.0 meq Mg/100g, broadcast 20 to 25 lb Mg/A and work into the seedbed before planting. If deficiency symptoms appear, spray with 10 lb Epsom salts in 100 gal water/A. Mg can also be supplied in dolomite, which is a liming material and reduces soil acidity to about the same degree as ground limestone. Dolomite should be mixed into the seed bed in the fall. BORON (B): No consistent responses of onions to the application of B have been observed in western Oregon. Where the soil test for B is below 0.25 ppm growers may wish to make a trial application of 2 lb B/A. Too much B fertil- izer can be highly toxic and suggested rates of B application should not be exceeded. B should be evenly distributed over the field and not banded. ZINC (Zn): The application of Zn has increased the yield of onions where soils have been deficient. When the soil test for Zn is below 2 ppm broadcast 10 lb Zn/A before planting or include 3-4 lb Zn/A in the fertilizer band. A broadcast application of 10 lb Zn/A should supply Zn needs for 2 or 3 years. COPPER (Cu): Muck soils tend to be deficient in Cu and "fix" Cu. If Cu has not been applied for 3 years , apply 15-25 lb Cu/A to the soil before planting, OR two foliar applications of 1-2 lb Cu in 100 gal water /A may be applied to onion leaves. Soil Cu applications need not be repeated every year. The best indicator for copper is leaf analysis. Consider copper applications when leaf copper levels are below 4 ppm. OTHER NUTRIENTS: Responses of onions to nutrients other than those discussed in this guide have not been observed in western Oregon. LIME: Experimental work on the muck soils of western Oregon has shown that onions will produce good yields over a fairly wide range of muck soil acidity. Lime applications should be considered when the soil pH is 5.5 or below. Keep muck soil pH between 5.6 and 6.0. The liming rate is based on 100-score lime. A lime application is ef- fective over several years. If the OSU soil test Apply this amount for pH reads: of lime (Tons/A): below 5.0 4-5 5.0-5.5 2-4 over 5.5 0 Lime should be mixed into the soil in the fall. For acid soils low in magnesium (Mg) (less than 1.0 meq Mg/100 g of soil) 1 Ton/A of dolomite lime can be used as a Mg source. Dolomite and ground limestone have about the same ability to neutralize soil acidity. Do not apply lime when the muck soil pH is above 6.0. Decreased yields have resulted in Willamette Valley experiments when liming raised the soil pH to 6.5. IRRIGATION Onions are shallow-rooted, and unless moisture supply is constant, they bulb early and the resulting sizes may be small. Light, frequent irrigations should be used when onions are small to minimize leaching of nitrogen from the root zone. Increase water applications as plants and roots increase in size. Maintaining moisture near the surface, at the onion stemplate is important in root generation. Onion roots generate at the stemplate only when moisture is present. Proper moisture management is important in alleviating pink root problems, general root health, and therefore bulb growth vigor. Also, main- taining an even soil moisture is important in reducing incidence of double-c- enter bulbs. Irrigation should thoroughly wet the soil to the 24 in. depth. In west- ern Oregon, 15-20 inches of water may be required. Watering should be termi- nated after the bulbs have reached full size, and tops have begun to fall. In overwintering onion production, use fall season water sparingly. Apply only enough water to establish a good stand, and enough growth so that onions will over-winter successfully. Onion plants should be about 1/4 inch in diameter as they go into the winter and go dormant. In spring and early summer, irrigate as necessary to maintain vigorous growth. Irrigation is generally terminated in June, prior to harvest. Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application. HARVESTING, HANDLING, CURING, AND STORAGE In western Oregon, harvest may range from the 20th. of August to the 20th. of October with the prime harvest season being from the first to the end of September. The average yield of storage onions in Western Oregon is approximately 20 tons/acre with good yields of about 25 tons/acre. Studies on the effect of harvest date on yield indicate that yield of bulb onions increases dramatically in the 4 weeks before 100% tops-down. In one study, yields increased approximately 10,500 lbs./acre from the start of top-fall (at 12% tops-down) to 100% tops-down, while mean bulb weight in- creased 2.25 oz. Furthermore, after the start of 100% tops down, yield increased by 2900 lbs./acre for the next 5 days (Davis, G.N. and H. Jones). As onions mature, tops begin to fall and dry. Sprout inhibitors are applied when onions are intended for long term storage. They are applied when tops are about 50% down, and there are 5 to 8 green leaves per bulb to absorb and translocate the sprout inhibitor. Do not apply sprout inhibitors when temperatures exceed 80-85 F to avoid crystallization on leaf surfaces. Use of a spray adjuvant is suggested . Avoid early sprays before maturity to reduce spongy onions. Maleic hydrazide (Royal MH-30) at 2 lbs ai/A is most commonly used. Apply in sufficient water to insure adequate coverage. CONSULT LABEL FOR LATEST INFORMATION ON APPLICATION RATES, TIMING AND PRECAUTIONS. Research indicates that, from the standpoint of maximum storage life (before bulb sprouting) optimum harvest would be when onion foliage is still partially (30-40%) erect, and long before maximum yield is attained (when tops are completely down and dry). Since yields may increase 30-40% between the stage when tops begin to go down, and the leaves are fully down and dry, it is tempting to leave onions to cure in the field as long as possible. The optimum time for harvest therefore, must be a balance between highest yields and reduced bulb storage quality. Furthermore excessively field-drying onions increases the risk due to bald onions in storage. DIGGING AND WINDROWING To facilitate curing onions for harvest and storage, onion rows are undercut, lifted and windrowed for field curing. Rod-weeder diggers and knife undercutters are most common. After an appropriate interval, the undercut onions are lifted and windrowed. This may be done with tops on or tops may be removed in the windrowing operation. Onions are also commonly windrowed with tops on to protect them from sunscald. Windrows may also be mechanically "fluffed" to facilitate curing. TOPPING Onions may be topped or harvested and stored with tops on. Topping may be done by hand or by machines such as the Vegi-Vac, Top-Air. These machines perform the lifting, topping and windrowing operations at the same time. When onions are allowed to cure without windrowing, machines can also harvest, top and load all in one operation. With good air movement and proper placement of onions in storage, onions have been found to store best with their tops on, however, keeping the tops on may complicate removal of onions from bulk storages and necessitates extra handling at packing time. If onions are to be bulk-stored it is best to store them without their tops. This facilitates handling, loading and unloading the storage. Onions that are to be stored in bins are usually stored with tops on. If onions are to be topped and stored, tops must be totally dry, or only the dry portion cut and removed. Cutting through any portion of the top while it is still green or moist may result in excessive Botrytis neck rot in storage. When all or a portion of the onion top is left on, the remaining tops are removed during grading and packing using roller toppers at the storage or packing facility. In the field, mechanically undercut and windrow "storage types" and pearl onions when 65-100% of the tops are down and cure by windrowing in the field. Machine "fluffing" of the windrow a few days after digging will shorten the drying period. This should also be done after each rainfall. After field drying has occurred, the onions may be topped and placed in storage buildings. Specialized harvesters are available for the various types of onions. Early market and "overwinter" onions for immediate sale or short-term storage are mechanically undercut and may be green-topped by hand or machine and partly cured in sacks or boxes in the field prior to packing. Since these onions are not to be stored, complete curing of necks and scales is not as important. When these onions are intended for storage, complete curing is manda- tory. Care must be exercised in handling these onions to guard against sun-scald and damage since these onions are much more succulent and have very few protective scales. When mechanically undercut and windrowed for curing, be sure onion tops provide adequate protection from sun-scald during periods of high sunlight and temperature (above 90 F). Cull onion disposal: Oregon Department of Agriculture regulations specify rules for cull onion disposal in order to minimize the spread of diseases. Consult these, for rules appropriate to your production area. In western Oregon, many of the cull onions are disposed of as sheep feed. Due to certain chemical constituents of onion, their use in animal feed is restricted by animal species and feed concentration. STORAGE (quoted form USDA Ag. Handbook #866): Storage may be either in bags, crates, in pallet boxes that hold about a half ton of loose onions, or in bulk bins. Bags of onions are frequently stored on pallets and should be stacked to allow proper air circulation. Modern air-cooled storages have forced ventilation systems in which air, heat- ed if necessary, is introduce through floor racks beneath the bins of onions. Onions in bins are stored about 10 to 15 feet deep, but soft onions at the bottom may be distorted in shape. Onions are held in either common or cold storage. The storage quality of onions is influenced by cultivar and by the conditions under which they are grown and stored. Onions should be adequately cured in the field, in open sheds, or by artificial means before or in storage. Adequate curing in the field or in open sheds may require 2 to 4 weeks, depending on the weather. The best skin color develops at 75 to 90 F. and 60-75% relative humidity. The most common method of curing in northern areas is by forced ventilation in the storage by blowing heated air at 75 to 85 F through the onions at 2 cf./m. air flow per cubic foot of onions. Electric or gas-fired infrared radiation has been shown to be an effective heating system for rapid curing. Onions are considered cured when the neck is tight and the outer scales are dry and will rustle. This condition is reached when onions have lost 3 to 5% of their weight. If not adequately cured, onions are likely to decay in storage. The most common form of decay is gray mold rot, which occurs at the top of the bulb - whence its name "neck rot". In the northern onion-growing states, onions of globe types are general- ly held in common storage. Average winter temperatures in the principal northern onion-producing states are sufficiently low to permit common storage during the winter months. However, they should not be held after early January unless they have been treated with maleic hydrazide in the field to reduce sprout growth. Refrigerated storage is often used for onions to be marketed late in the spring. Onions to be held in cold storage should be placed there immediately after curing. A temperature of 32 F will keep onions dormant and reasonably free from decay, provided the onions are sound and well cured when stored. Air circulation should be sufficient to prevent heating and to remove moisture from within bins or sacks. Sprout growth indicates too high a storage temperature, poorly cured bulbs, or immature bulbs. Root growth indicates too high a relative humidity. A comparatively low relative humidity (65 to 70 %)is recommended for success- ful storage of onions. However, humidities as high as 85 % and forced-air circulation have given satisfactory results. Higher humidities, at which most other vegetables keep best in storage, dispose onions to root growth, rot, and surface mold. Excessive drying however may result in cracking of the outer bulb scales and bald onions. Globe onions can be held for 6 to 8 months at 32 F. The mild types such as those produced in the Walla Walla area of Washington can be held in cold storage; but, because of their poorer keeping qualities, they usually are stored for much shorter periods (1-2 months at 32 F.) than the standard globe cultivars. Onions will sprout and decay rapidly when stored at temperatures between 40 and 50 F. However, they will not sprout or be as susceptible to decay if they are in the resting stage, which lasts 30 to 60 days. The resting of most cultivars is completed during storage at 32 F. Onions are damaged by freezing, the damage appearing as water soaked scales when the thawed onions are cut. Onions only slightly frozen may reco- ver with little perceptible injury if allowed to thaw slowly and without hand- ling. Translucent scale of onions (a clearing of the scales which somewhat re- sembles freezing injury) has been found particularly in large bulbs stored several months. Prompt cold storage after curing reduces its prevalence. Onions should not be stored with other products that tend to absorb odors. They may be stored with garlic. When onions are removed from storage in warm weather, they are apt to sweat because of moisture condensation. This may favor decay. Warming onions gradually, for example, to 50 F over 24 to 36 hours with good air movement should avoid this difficulty. Onions can also be stored at high temperatures of 85 to 95 F for short periods before marketing or before processing. Dehydrated flakes produced from onions that had been stored at 85 F for 4 months discolored less in stor- age than flakes made from onions stored at cold temperatures. Controlled atmosphere storage tests with onions have been only moder- ately successful. An atmosphere of 5% carbon dioxide with 3% oxygen reduced losses from sprouting and root growth. In Oregon curing is generally accomplished by forcing air of a low rela- tive humidity through the bottom of the onion pile to the top. One to two cubic feet of air per minute for each cubic foot of onions is recommended, with the higher air-flow rate used initially to remove surface moisture and seal necks. If the weather is cool and wet, forced air at 75 to 85 F and 60- 70% relative humidity is recommended. If the onions are also wet, forced air at 85 F and a relative humidity of 25-35% relative humidity should be used as soon as storage loading is completed. This should be continued until the outer skins and neck are dry. The crop should then be allowed to cool gradu- ally slowly reducing its temperature by drawing outside air, anytime the stor- age air has a humidity above 75% and the outside air is cooler than the onions, until the temperature of the onions reaches the desired holding tempe- rature, or (32 F and above). After curing, the relative humidity in the storage should be maintained between 60 and 70%. If the storage is too dry, the outer bulb scales will crack excessively, resulting in bald onions during packing. The less fluctua- tion the better. During dry, cold weather (above 32 F) the doors may be opened or the fans used to circulate cold air throughout the pile. Be sure that the dew point of the outside air that is used is always 2 or more degrees above the temperature of the onions in the pile, otherwise water may condense on the onions. During wet weather or very cold weather (below 32 F) the building should remain closed and the air within should be recirculated periodically or outside and inside air may be mixed as needed to keep onions cool and dry. Consult also other appropriate storage publications such as Oregon State University PNW 277 Onion Storage Guidelines for Commercial Growers. PACKAGING Dry onions are sorted, cleaned sized and graded, just prior to packag- ing. They are commonly packaged in 50 lb. sacks. Some are now also packaged in consumer packs of 2, 5 and 25 lbs. mesh sacks. SHIPPING Dry bulb onions from the northwest are shipped across the U.S.A. at ambient temperatures but protected from freezing. When shipped international- ly, several methods are used. When non-refrigerated containers are used, one door should be removed to eliminated the build up of humidity from onion respiration. Shipping compa- nies can arrange to do this. When refrigerated containers are used, as is necessary with sweet onions that have limited storage characteristics, arrangements must be made to bring the temperature in the container to ambient 24-48 hours before arrival at destinations where local humidity may result in the onions getting wet from condensation. Arrange for the shipping company to raise the container temperature from 32 F. to 50 F. 2 days before arrival, then from 50 F. to 70 F. 1 day before arrival. This gradual increase in temperature will prevent condensation on onions upon their removal from the container and reduce risk of spoilage. PEST CONTROL FOR ONIONS, DRY BULB THE PESTICIDES LISTED BELOW, TAKEN FROM THE PACIFIC NORTHWEST PEST CONTROL HANDBOOKS, ARE FOR INFORMATION ONLY, AND ARE REVISED ONLY ANNUALLY. BECAUSE OF CONSTANTLY CHANGING LABELS, LAWS, AND REGULATIONS, OREGON STATE UNIVERSITY CAN ASSUME NO LIABILITY FOR THE CONSEQUENCES OF USE OF CHEMICALS SUGGESTED HERE. IN ALL CASES, READ AND FOLLOW THE DIRECTIONS AND PRECAUTION- ARY STATEMENTS ON THE SPECIFIC PESTICIDE PRODUCT LABEL. USE PESTICIDES SAFELY! Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use. Read the pesticide label--even if you've used the pesticide before. Follow closely the instructions on the label (and any other directions you have). Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use. WEED CONTROL Cultivate as often as necessary when weeds are small. Proper cultiva- tion, field selection and rotations can reduce or eliminate the need for chemical weed control. THE WEED TREATMENTS LISTED BELOW ARE TAKEN FROM THE PACIFIC NORTHWEST WEED CONTROL HANDBOOK, AND ARE FOR INFORMATION ONLY. CONSULT PRODUCT LABELS FOR CURRENTLY LEGAL REGISTRATIONS, RATES, AND COMPLETE INSTRUCTIONS. WEED MANAGEMENT GENERAL STRATEGY Onions are a noncompetitive crop with short, vertical leaves that fail to form a canopy that suppresses weeds. Weeds are managed with selective herbicides combined with frequent cultivation. Winter cover crops or crop rotations enhance both soil and weed management. ______________________________________________________________________________ STALE SEEDBEDS FOR VEGETABLE PRODUCTION Stale seedbeds are sometimes used for vegetable production when other selec- tive weed control practices are limited or unavailable. The concept depends on controlling the first flush of emerged weeds before planting or emergence of the crop followed by minimal soil disturbance which reduces subsequent weed flushes during establishment of the crop. Following establishment, other weed control practices including cultivation or use of other herbicides can be used. 1. Prepare a seedbed, preferably 2 to 3 weeks before planting to achieve maximum weed seed germination near the soil surface. Soil temperatures and moisture must be reasonable or results will be erratic. 2. Plant the crop with minimum soil disturbance. Otherwise, new weed seed will be exposed to favorable germinating conditions. 3. Just before or after planting but before crop emergence, treat the field by flaming or with herbicide to kill all germinated or exposed weeds. Weed Treatment Active Ingredient Per Acre and Application Comments ------------------------------------------------------------------------------ Flaming Use liquid propane or similar fuel-burning equipment to quickly sear the weeds, but not consume them with flame. ------------------------------------------------------------------------ paraquat 0.625 to 0.94 lb ai/A Gramoxone Extra (see remarks) Restricted-use pesticide. Do not ingest or inhale spray mist. Wearing protective face shields, respirators, and clothing is advised. Apply during or after planting, but before crop emergence. Add a nonionic surfactant or crop oil concentrate according to label specifications, taking care to avoid anionic formulations that react in the tank to form insoluble precipitates. Exposed crop plants will be killed. Do not apply preplant or preemergence to soils lacking clay minerals, such as peat, muck, pure sand, or artificial planting media. (Acts as contact; absorbs energy produced by photosynthesis forming peroxides that disrupt living cells.) ------------------------------------------------------------------------ glyphosate Consult Labels Roundup Roundup RT (E. Washington and Idaho only) or Honcho + nonionic surfactant Apply to actively growing weeds either preplant in conjunction with site prepartion or preemergence crops listed on the label. Consult label for specific rates, times of application, and perennial species controlled. Generally 1 to 1.5 lbs ai/A should be used for annual weeds, while perennial weeds require higher rates. Addition of a surfactant or ammonium sulfate improves activity when weeds are stressed. Do not apply more than 8 lbs. ai/A per year, nor plant nonlabeled crops within 12 months following application. (Inhibits production of 3 amino acids and protein synthesis.) ______________________________________________________________________________ ONIONS--MINERAL SOILS Weed Treatment Active Ingredient Per Acre and Application Comments ------------------------------------------------------------------------------ bensulide 3 to 6 lb ai/A Prefar (spring planted bulb onions only) Idaho, Oregon and Washington special local needs (SLN-ID840011 and OR840041 and WA880015) only. Apply 3 lb rate in fall in 10-12 inch band and bed-up by throwing soil from furrows over the sprayed band, or broadcast 6 lb rate and incorporate before bedding up in the fall. In spring, drag-off bed tops with spiketooth harrow being careful not to expose soil beneath the treated layer. Plant in center of beds. (Inhibits roots of seedlings). ------------------------------------------------------------------------ DCPA 6 to 9 lb ai/A Dacthal Apply after planting to moist soil surface before weeds and onions emerge. In eastern Oregon when rainfall is sparse, shallow incorpora- tion using a nailboard has improved weed control. Results are improved with overhead irrigation immediately following application. Consult label for planting sensitive crops within 8 months. (Inhibits mitosis). ------------------------------------------------------------------------ oxyfluorfen 0.12 to 0.25 lb ai/A Goal Causes skin irritation--Wear protective gear. Apply postemergence to onions with 2 fully developed true leaves while broadleaf weeds have less than 4 true leaves. Multiple treatments may be required as new weeds emerge, but do not exceed 0.5 lb ai/A. Use a clean sprayer and do not mix with oils, surfactants, or other agricultural chemicals. Do not apply to onions under any stress. Slight leaf curl may occur and young plants sometimes become prostrate on the soil surface for 1 to 2 days, but yields have not been reduced. Do not apply within 60 days of harvest. (Acts as a selective contact that disrupts cell membranes). Special local needs (SLN-OR-90026 and WA-910012 allows application through sprinkler irrigation systems. Read and follow label instruc- tions precisely regarding irrigation interval and all chemigation specifications to minimize environmental hazards. ------------------------------------------------------------------------ monocarbamide 10 to 30 gal dihydrogensulfate product/A Enquik Apply in sufficient water volume for full coverage when first true leaf is as tall as flag leaf. Repeat applications may be necessary. Do not apply in presence of free moisture or within 5 days after a foliar pesticide application. Repeat as required until crop is 8 inches tall; then direct sprays between rows. Do not apply to green onions after they reach 8 inches to avoid scarring. Adjust fertilizer rates for nitrogen and sulfur. (Acts as contact). ------------------------------------------------------------------------ bromoxynil 0.25 to 0.38 lb ai/A Buctril Do not ingest or inhale spray mist and prevent contact with skin. Wearing protective face shields, respirators, and clothing is advised. For use in Idaho and east of the Cascades in Oregon and Washington only. Apply in 50 to 70 gal water for thorough coverage when onions have 2 to 5 true leaves. Apply on sunny days when plants are dry and humidity is low. Do not apply west of the Cascades or when the protective waxy cuticle on onion leaves may be thin or damaged. Application can be preemergence, but irrigation or rainfall within 2 days of application may result in crop injury. Do not add adjuvants. Injury can sometimes occur even under ideal conditions. (Precise action unknown; acts as a selective contact that disrupts cell membranes). ------------------------------------------------------------------------ pendimethalin .5 to 1.48 lb ai/A Prowl (dry bulb onions only) Apply postemergence when onions have 2-9 true leaves and at least 45 days before harvest. Adjust rates according to soil texture. Rainfall or overhead irrigation is needed within 10 days for activation. Be aware of crop rotation restrictions including sugar beets, winter wheat, and winter barley. (Inhibits mitosis, both in shoots and roots). ------------------------------------------------------------------------ trifluralin 0.38 to 0.63 lb ai/A Treflan (broadcast rates) Apply at lay-by as a directed spray to the soil between rows and incor- porate immediately with sweeps or rolling cultivators. Use proportion- ately less for treating area between rows only. Do not apply to soils with more than 3.5% organic matter or reduced herbicide activity will result. Do not apply preplant or preemergence or within 60 days of harvest. Remove emerged weeds before application. Consult label for planting sensitive crops within 12 months. (Inhibits mitosis, both in shoots and roots). ------------------------------------------------------------------------ paraquat 0.625 to 0.94 lb ai/A Gramoxone Extra A restricted-use pesticide. Do not ingest or inhale spray mist. Wearing protective face shields, respirators, and clothing is advised. Apply before, during, or after planting, but preemergence to crop to control emerged weed seedlings only. Add a nonionic surfactant or crop oil concentrate according to label specifications, taking care to avoid anionic formulations that react in the tank to form insoluble precipi- tates. Preharvest interval is 60 days. (Acts as contact; absorbs energy produced by photosynthesis forming peroxides that disrupt living cells. ------------------------------------------------------------------------ fluazifop Consult Label Fusilade 2000 Identify grasses and adjust rates depending on suceptibility and stage of weed growth according to label instructions. Apply to actively growing grasses as a directed spray with 1% crop oil or 0.25% nonionic surfactant. Erratic results often occur when grasses are stressed from lack of vigor, drought, high temperature, low fertility, grass stage of growth, and unknown environmental factors. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescies resist treatment. Do not harvest within 45 days of treatment or apply more than 6 pints product per year. Grazing is prohibited. (Inhibits fattyacid production, cell membranes, and new growth.) ------------------------------------------------------------------------ sethoxydim 0.19 to 0.28 lb ai/A Poast Identify susceptible grasses and apply at optimum growth stage listed on the label. Add 2 pints/A nonphytotoxic crop oil concentrate to improve leaf absorption. Erratic control often occurs when grasses are stunted or stressed from drought, high temperatures, or low fertility. Resis- tant grasses include annual bluegrass and all fine fescues, whereas quackgrass can be suppressed. Do not apply within 30 days of harvest, nor exceed 4.5 pints/A per season. (Inhibits fatty acid production, cell membranes, and new growth.) ______________________________________________________________________________ MUCK OR PEAT SOILS Weed Treatment Active Ingredient Per Acre and Application Comments ------------------------------------------------------------------------------ oxyfluorfen 0.12 to 0.25 lb ai/A Goal Apply postemergence to onions with 2 fully developed true leaves while broadleaf weeds have less than 4 true leaves. Multiple treatments may be required as new weeds emerge, but do not exceed 0.5 lb ai/A. Use a clean sprayer and do not mix with oils, surfactants, or other agricul- tural chemicals. Do not apply to onions under any stress. Slight leaf curl may occur and young plants sometimes become prostrate on the soil surface for 1 to 2 days, but yields have not been reduced. Do not apply within 60 days of harvest. (Acts as a selective contact that disrupts cell membranes). ------------------------------------------------------------------------ monocarbamide 10 to 30 gal product/A dihydrogensulfate Enquik Oregon special local needs (SLN-OR850029) label. Apply in sufficient water volume for full coverage when first true leaf is as tall as flag leaf. Repeat applications may be necessary. Do not apply in presence of free moisture, nor within 3 days after a foliar pesticide applica- tion. Do not apply to green onions after they reach 8 in. to avoid scarring. Adjust fertilizer rates for nitrogen and sulfur. (Acts as contact). ------------------------------------------------------------------------ fluazifop Consult label Fusilade 2000 Identify grasses ad adjust rates depending on susceptibility and stage of weed growth according to label instructions. Apply to actively growing grasses as a directed spray with 1% crop oil or 0.25% nonionic surfactant. Erratic results often occur when grasses are stressed from lack of vigor, drought, high temperature, or low fertility. More mature grasses and quackgrass can be controlled but may require 2 applications. Annual bluegrass and all fine fescues resist treatment. Do not harvest within 45 days of treatment or apply more than 6 pints product per year. Grazing is prohibited. (Inhibits fatty acid production, cell membranes, and new growth). ------------------------------------------------------------------------ sethoxydim 0.19 to 0.28 lb ai/A Poast Identify susceptible grasses and apply at optimum growth stage listed on the label. Add 2 pints/A nonphytotoxic crop oil concentrate to improve leaf absorption. Erratic control often occurs when grasses are stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues, whereas quack- grass can be suppressed. Do not apply within 30 days of harvest, nor exceed 4.5 pints/A per season. (Inhibits fatty acid production, cell membranes, and new growth). ------------------------------------------------------------------------ paraquat 0.625 to 0.94 lb ai/A Gramoxone Extra A restricted-use pesticide. Do not ingest or inhale spray mist. Wearing protective faceshields, respirators, and clothing is advised. Apply before, during, or after planting, but preemergence to crop to control emerged weed seedlings only. Add a nonionic surfactant or crop oil concentrate according to label specifications, taking care to avoid anionic formulations that react in the tank to form insoluble percipi- tates. Preharvest interval is 60 days. (Acts as contact; absorbs energy produced by photosynthesis forming peroxides that disrupt living cells.) ______________________________________________________________________________ ONIONS-SPROUT INHIBITION Weed Treatment Active Ingredient Per Acre and Application Comments ------------------------------------------------------------------------------ maleic hydrazide 2 lb ai/A Royal MH-30 Apply when bulbs are fully mature with soft necks and 5 to 8 green leaves, or when approximately 50% of the tops have fallen, but are still green. Should be applied at temperatures below 80 to 85 F to avoid crystalization on leaf surfaces. Use of a spray adjuvant is suggested in arid regions west of the Rocky Mountains. Avoid early sprays before maturity to reduce spongy onions. Do not treat seed onions. ______________________________________________________________________________ ______________________________________________________________________________ INSECT CONTROL Proper rotations and field selection can minimize problems with insects. THE PESTICIDES LISTED BELOW ARE TAKEN FROM THE PACIFIC NORTHWEST INSECT CONTROL HANDBOOK, AND ARE FOR INFORMATION ONLY. CONSULT PRODUCT LABELS FOR CURRENTLY LEGAL REGISTRATIONS, RATES AND COMPLETE INSTRUCTIONS. Insect and Description Control, Active Ingredient Per Acre --------------------------------------------------------------------------- Cutworms and Armyworms Lannate - 0.45 to 0.9 lb Different species Bacillus thuringiensis - 1 to 2 Small to large larvae that chew qt. Use a spreader-sticker to holes in bulbs and leaves. enhance control. Phosdrin - 0.25 to 0.5 lb Climbing cutworms only. Permethrin - 0.1 to 0.3 lb --------------------------------------------------------------------------- Brown wheat mite Petrobia latens Small, light tan to brown active mite. Damages leaves. --------------------------------------------------------------------------- Bulb mites soil fumigation Rhyzoglyphus sp. Small, white mites capable of causing damage to developing bulbs and intro- ducing pathogenic fungi. Damage can continue in storage. -------------------------------------------------------------------------- Onion thrips azinphosmethyl - Thrips tabaci 0.5 to 0.75 lb Adults are small, pale yellow to malathion - 1 to 2 lb light brown in color with feath- ery wings. Young are pale yel- Phosdrin - 0.5 lb lowish-green and wingless. They feed on onion foliage and diazinon - 0.5 lb cause it to become white, kill- ing the tops and reducing Penncap-M - 0.5 lb Apply yields. only to dry onions. Do not use on green onions. WARNING: Microencapsulated methyl methyl parathion - 0.5 to parathion (Penncap-M) should never 0.83 lb be sprayed on blooming weeds in onion fields or adjacent fields. Permethrin - 0.15 to 0.3 lb If misused, this formulation is especially hazardous to honey bees Metasystox-R - 0.75 lb Use and other pollinating insects be- only on Spanish bulb onions. cause of its strong tendency to contaminate pollen. Vydate L - 0.25 to 0.5 lb Do not harvest tops. Note: Dasanit applied in the seed furrow for onion maggot control sup- Lannate - 0.45 lb presses thrips populations in the early season. This may allow Pyrellin - 1 to 2 pt growers to reduce foliar sprays. Oregon, Idaho, and Washington only, 24 c. Caution: Dasanit may reduce onion stands in sandy/light soils. --------------------------------------------------------------------------- Onion maggot diazinon - 2 to 4 lb Delia antiqua Dyfonate - 1 lb Use Dyfonate Adult is a fly, pale to dark gray only where organic matter in color, less than inch in exceeds 10 percent. size. Larvae are legless, blunt white maggots that kill seed- diazinon - 1 lb lings and damage bulbs of Furrow applications only. older plants. malathion - 1.5 to 2 lb Use for adult control. Lorsban 4E - 0.034 lb ai/1000 row ft. Apply as in-furrow treatment on direct-seeded dry bulb onions only. Lorsban 15G - 0.034 lb ai/1000 row ft. Apply as in-furrow treatment on direct-seeded dry bulb onions only. --------------------------------------------------------------------------- Pea leafminer diazinon - 0.5 lb Liriomyza huidobrensis Larvae of tiny fly. Mine in leaves. When abundant, cause leaves to wither from tip downward. --------------------------------------------------------------------------- Wireworms diazinon - 3 to 4 lb Limonius spp. Telone II or C-17 preplant Brown, jointed larvae of click beetles. Kill young plants, weaken older ones. --------------------------------------------------------------------------- --------------------------------------------------------------------------- DISEASE CONTROL Proper rotations, field selection, sanitation, spacings, fertilizer and irrigation practices can reduce the risk of many diseases. Fields can be tested for presence of harmful nematodes. Using seed from reputable seed sources reduces risk from seed born diseases. THE PESTICIDES LISTED BELOW ARE TAKEN FROM THE PACIFIC NORTHWEST DISEASE CONTROL HANDBOOK, AND ARE FOR INFORMATION ONLY. CONSULT PRODUCT LABELS FOR CURRENTLY LEGAL REGISTRATIONS, RATES AND COMPLETE INSTRUCTIONS. ONION -- BASAL ROT Cause: Fusarium sp., soilborne fungi. The disease causes losses principally of green onions and garlic. Symptoms: Yellowing, wilting, and lack of vigorous growth. Red-brown rot where roots are attached to the base. The rot and discoloration usually affect all of the base and upwards into the scales. Sometimes a weft of mycelium develops over the surface of the base or between the affected scales. Rot may progress in storage under situations where elevated moisture levels exist. Infection is often associated with pink root, maggots, or other insect injury. ~Control: 1. Protect plants from insect, fertilizer, or other injury. 2. Rotate crops use well-drained soil. 3. Some soil chemicals have been tried but at present none are being recom- mended. In a test in Malheur County, Oregon, the following varieties had less basal rot when compared to a number of other varieties: `Golden Cascade', `Cima', `Oro Grande', `Valient', and `Cashe'. Other onion varieties described as tolerant but not tested in Oregon are `Bronze Reserve', `North Star', `Sassy Brassy', and `Sentinel'. --------------------------------------------------------------------------- ONION -- DOWNY MILDEW Cause: Peronospora destructor, a fungus. This organism survives the winter on infected plants or on old onion plant material in the field. Symptoms: Bluish, downy spots appear on the leaves. Plants may be dwarfed, distorted, and pale green. Spots develop first with a water-soaked appearance, later taking on a purplish shade. In dry climates, the leaf spots may be white in appearance. As the spots enlarge, often girdling the leaves, a whitish mold develops on the surface of the spot, later turning black. Secondary leaves may develop on infected plants, retarding normal bulb development. Plants are not often killed, but bulb quality is poor and often spongy. ~Control: 1. Avoid poorly-drained soils. 2. Practice a 3-year crop rotation where possible. 3. Destroy onion plant refuse and cull piles. 4. Eradicate perennial onions or wild onions. 5. There are no resistant varieties of the types grown in Oregon. 6. Spray with one of the following: a. Mancozeb (dry onions only) at 1.6 to 2.4 lb ai/100 gal/A. b. Maneb at 1.6 to 2.4 lb ai/A. c. Ridomil MZ58 at 1.5 to 2 lb product/A. d. Ridomil/Bravo 8l W at 1.5 to 2 lb product/A. e. Fosetyl-Al (Aliette) at 1.6 to 2.4 lb ai/A. f. Fixed copper. Residues: Mancozeb - Tolerance 0.5 ppm. Do not apply within 7 days of harvest. Do not apply to exposed bulbs. Maneb - Do not apply more than 16.8 lb ai/A/season. Do not apply within 7 days of harvest. Fosetyl-Al -- Do not apply within 7 days of harvest. Ridomil/Bravo 81W - Do not apply to dry bulb onions within 7 days of harvest or to green onions within 21 days of harvest or more than 4 times on green onions. See product label for rota- tion restrictions. --------------------------------------------------------------------------- ONION -- NECK ROT Cause: Botrytis allii, a fungus. This organism survives the winter on dead plant parts in the soil and on infected bulbs. The most common causes for severe losses are (1) use of excessive amounts of nitrogen which delay maturity of the crops, (2) irrigation and/or rainfall late in the season, (3) inadequate or improper curing, and (4) improper storage. Symptoms: The organism appears on maturing bulbs just prior to harvest and during harvest, with infection occurring through the neck tissue or through wounds in the bulbs. Frequently infection enters the neck as a result of topping the onions prior to proper drying of soft susceptible top tissues. The fungus moves rapidly into the succulent onion bulb in the neck region, producing a water-soaked appearance. Yellow discoloration often appears. Between the onion scales a gray mold develops, later producing small, black bodies (sclerotia) which develop as a solid layer around the neck. Ultimately the bulbs break down to a soft mass, and secondary infections follow. ~Control: The tops should be allowed to mature well, and the onions should then be lifted or undercut. If normal dry weather prevails, the onions should then cure on the ground for 6 to 10 days. Bruising and mechanical injury in topping and storing should be kept to a minimum, and the onions should be stored in well-ventilated houses at temperatures of 32 F or just slightly higher. Higher temperatures should be used when humidity cannot be held below 75 percent RH. There are no fungicides that consistantly control neck rot even though EPA has granted several labels for this use. --------------------------------------------------------------------------- ONION -- NEMATODE (Stubby Root) Cause: Paratrichodorus allius. An ectoparasitic nematode that overwinters in the soil. The largest populations of nematodes and conspicuous plant symptoms occur during cool, damp springs. Symptoms: Roots are extremely short with yellow to brownish cast plants are stunted usually in spots in the field. ~Control: 1. Telone II at 4.5 to 36 gal/A (follow label recommendations). Fumigate in the fall. OR 2. An in-furrow spray of 1.5 to 2 gal Vydate L (broadcast basis) in 20 to 50 gal of water or .75 to 1 gal Vydate L (broadcast basis) as an in-furrow drench in 100 to 150 gal of water are usually adequate to control the problem. In situations with extremely high nematode presence, two or three postemergence applications may be made. See label--Oregon only (SLN OR 810033). Residues: Telone II. Preplant soil treatment. Seal soil for 7 to 14 days then aerate 1 week for each 10 gal/A applied--longer in case of heavy rains or temperatures below 60 F--until the odor of the fumigant is gone. Do not treat extremely heavy soils. Do not apply near living plants. Considered to be a nonfood use. Soil fumigants. If fall fumigation is done, beds will be free of fumigant by spring planting. Vydate. Limit 14 days before harvest. Such late applications will not be effective in any case. Sampling: Stubby-root nematodes are migratory ectoparasites (see Nematodes-- Life Histroy), and are found only in the soil. Before planting crops suscep- tible to stubby-root nematodes, soil samples should be taken with sufficient lead time to implement management procedures if necessary. If this is soil fumigation, it may be several weeks before crops can be planted. Fall sampling for crops to be planted the following spring is an excellent strate- gy. For diagnosis, submit both soil and onions containing roots. --------------------------------------------------------------------------- ONION -- PINK ROOT Cause: Pyrenochaeta terrestris, a fungus. This fungus may live in the soil saprophytically for several years. Symptoms: The disease may appear either in young seedlings or later throughout the growth of the onion. There is a yellowing of roots followed by a pinkish-colored root development. These take on a bright-pink shade and die. New roots produced thereafter become diseased and also die. As this process continues through the growing season, the bulbs lack normal development and are reduced in size and vigor with stunted tops. ~Control: 1. A crop rotation in which onions are planted only every 5 years will reduce the severity of infection however, some plants will be invaded by the fungus. 2. Use adequate fertilizer, irrigation, cultivation, etc., to stimulate rapid bulb growth. 3. Some partially resistant varieties of the sweet spanish type are avail- able. 4. Preplant soil fumigation with Telone C-17 is effective in control of the disease on mineral soils at the rate of 5.1 to 41 gal/A. Not effective on peat soils. Note: Fall fumigation is more effective than spring. 5. The varieties `El Capitan', `Avalanche', `Bullseye', `Bravado', `Merit', `Durango', `Yula', `Armada', `Valdez', and `Fiesta' were bred for resistance. `Yellow Globe Danvers' types are resistant. Caution: Since the fumigation must be done prior to planting, it is important that the planting row be directly over the fumigated soil when only the planting row is treated. Variations of a few inches can cause complete loss of control. Not effective on peat soils. --------------------------------------------------------------------------- ONION -- PURPLE BLOTCH Cause: Alternaria porri, a fungus. The organism overwinters on dead, diseased onion trash in the field and on infected bulbs. Infection often follows injury caused by other fungi, e.g., Botrytis, or by sand or dust during windstorms. The spores require rain or persistent dew to cause infection. The optimum temperatures are 77 to 81 F. Almost no infection occurs below 55 F. The disease is sometimes severe in irrigated onion-growing areas of eastern Oregon. Symptoms: On the leaves a small, water-soaked area develops, which soon turns brown. As the spot enlarges, zones may appear, and it turns purplish. White margins often encircle the purplish centers. When the weather is moist, the surface of the spot usually becomes covered with a brownish-black, powdery fungus growth. Leaves with large spots turn yellow and are blown over by the wind. Infection of the leaves may be noticed by the presence of leaf spots very soon after infection has occurred, sometimes within 2 days. Bulb decay may occur during and after harvest. It shows first as a watery rot starting around the neck and is particularly noticeable because of the yellowish to wine-red discoloration in the neck region. As the fungus moves through the onion tissues, they dry and take on a papery texture toward the outside. `Sweet Spanish' onions are very susceptible to purple blotch. ~Control: The disease does not occur in Oregon with sufficient frequency to warrant an annual spray program. Spraying as soon as the disease occurs will prevent further spread of the disease. The variety `Fiesta' has tolerance. Other control practices which will reduce losses are: 1. Destroy old onion cull piles. 2. Handle and harvest with care, destroying any diseased onions. 3. Proper curing of bulbs in field--lift and allow to dry several days before topping. Spray: Mancozeb (dry bulb onions only) (Dithane M-45, Manzate 200)--1.6 to 2.4 lb ai/100 gal/A. Bravo 720 at 1.5 to 3 pt/a (2 pt maximum) on dry bulb onions in sufficient water to cover. Maneb at 1.6 to 2.4 lb ai/A. Do not apply more than 16.8 lb ai/A/season. Do not apply within 7 days of harvest. Ridomil/Bravo 8l W l.5 to 2.0 lb/A. Rovral WP--1.5 lb/A in 50 to 100 gal of water. Spray fixed copper. Several formulations and products are available. See product labels for rates. Tolerance: Mancozeb (dry bulb onions only)--Tolerance 0.5 ppm. Do not apply within seven days of harvest. Do not apply to exposed bulbs. Maneb--Tolerance 7 ppm. No time limitation. Bravo 720--Tolerance 5 ppm on green onions, 0.5 ppm on dry bulb onions. Do not apply within 14 days of harvest (green onions) or 7 days of harvest (dry onions). Do not apply more than three times per season on green onions. Do not apply to sweet spanish onions except in Idaho and Oregon. Ridomil/Bravo - See cautions under downey mildew. Rovral WP--Tolerance 0.5 ppm. Do not apply within 4 days of harvest. Copper: Exempt. --------------------------------------------------------------------------- ONIONS -- RUST (Seed Onions Only) Cause: Puccinia asparagi, a fungus. The fungus actually survives on asparagus which commonly grows wild along ditch banks of irrigated areas in southern Idaho and eastern Oregon. Symptoms: The uredial stage attacks the onion leaves and seed stalks. Light yellow to orange or reddish, powdery pustules develop. With pustules enlarge- ment, the leaves or seed stalks become girdled. The affected tissues at and above the girdling turn yellow and die prematurely, thus reducing seed yield. ~Control: Destroy wild asparagus or spray the asparagus and adjoining onions with mancozeb. Residues: See under Onion--Purple Blotch. --------------------------------------------------------------------------- ONION -- SEED TREATMENT Aids in control of smut, seed decay, and damping-off. Thiram-- or 2 t/lb or 1 lb product for 10 lb seed for smut. --------------------------------------------------------------------------- ONION -- SMUT Cause: Urocystis cepulae, a fungus. This fungus survives saprophytically in the infested soil for several years. It attacks only members of the onion family including onion, leek, and Welsh onion. Symptoms: The disease appears first in the stems of the young plant as it emerges. Infected areas have a raised blisterlike appearance near the ground level. These rupture to expose black powder masses of spores. Numerous seedlings are killed during the emergence period, and those which live produce distorted bulbs having darkish streaks and numerous smutty lesions. ~Control: 1. Pelleted onion seed using Thiram with a methocel sticker has been used in some areas. Such pelleted seed is applied at the rate of 5 lb/A. 2. Small onion sets and young onion plants may be set out in infested soil without apparent danger of infection. 3. Control smut by an in-furrow drench at seeding of mancozeb or Maneb at 2.4 lb actual/A (29,000 linear feet of furrow). --------------------------------------------------------------------------- ONION -- SOFT ROT OR STINKING ROT Cause: Unknown species of Pseudomonas and Erwinia. Symptoms: First symptoms appear in late June. Either the inner or outer whorl of leaves, but usually not both, become flaccid and rapidly change from green to white to brown and collapse to the ground. Soon the disease progresses to the apparently unaffected parts, with water-soaking and collapse following. After collapse of the foliage a watery, foul-smelling liquid exudes from the bulbs. Further spread of the disease is reduced by warm, dry summer weather. Slightly affected plants may recover, but usually are distorted and chlorotic. Bulbs infected late in the season may appear, but decay during storage. The disease does not spread from bulb to bulb in storage. This disease has been widely distributed in western Oregon onion-growing areas, and occurs in Oregon and Southwestern Idaho onion-growing areas. There is a lower incidence of this disease in furrow or rill-irrigated fields. ~Control: 1. Some control can be obtained by using water from deep wells, rather than from ditches. 2. Reduce mechanical injuries during cultivation and weeding. 3. Thoroughly cure onions before storing. --------------------------------------------------------------------------- ONION -- WHITE ROT Cause: Sclerotium cepivorum, a fungus. The fungus can remain viable in the soil for many years without the presence of the host--probably as long as 8 to 10 years. Other hosts include garlic, leek, shallot, and other allium sp. Symptoms: The leaves of a diseased plant decay at the base, turn yellow, wilt, and topple over. The older leaves collapse first. Roots are rotted and the plant can be easily pulled up. Fluffy mycelium may be present on the remaining roots and bulb. Affected bulbs may become watery and the outer scales cracked as they dry and shrink. Small (1/50 inch) sclerotia are formed in affected parts of the bulb and on the surface, often around the neck. The sclerotia are smaller and rounder than those of Botrytis (the cause of the neck rot dis- ease). ~Control: Idaho law forbids the import of sets, bulbs, or other material infected with white rot. Avoid the movement of contaminated soil or machinery into clean fields. Treatment of heavily infected areas of organic soils with 400 lb of methyl bromide/A tarped has been useful in reducing inoculum in infested fields. Incorporate 32-40 lb. of Botran 75 WP/A prior to seeding (see label for specific instructions). This treatment has been erratic on direct-seeded onions but is more effective when used on sets. OR Spray 2 lb of Ronilan 50 WP in a 4- to 6- inch band in 400 gal. of water/A or in a 2- to 4- inch band in 100 gal of water/A over the seed row. Apply at least 2 more applications of 2 lb. of Ronilan 50 WP in 100 gal of water/A at 4-6 week intervals. Residues: Botran--Soil application before seeding or spray to soil around sets or buds. Tolerance 5 ppm. Do not plant spinach as a follow-up crop in treated soil. Ronilan--Do not apply more than 10 lbs. Ronilan/A in one crop season. Do not apply within 18 days of harvest. Do not apply through any type of irrigation system. --------------------------------------------------------------------------- --------------------------------------------------------------------------- --------------------------------------------------- --------------------------------------------------- This information was adapted by the Oregon State University Extension Service from Oregon and Pacific NW publications as well as other vegetable production guidelines from public institutions in the U.S. and Canada. These guidelines are intended as a general guide for Oregon commercial vegetable producers. Address comments and questions to your County Extension Agent or Dr. N. S. Mansour, Department of Horticulture, Oregon State University, Corvallis, OR 9733l. --------------------------------------------------- ---------------------------------------------------