NOTES: For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 26 and Insecticides Alphabetical Listing by Trade Name for more information on these insecticides.
The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.
The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.
The symbol OG indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.
Two genera of mites are known to infect species of Allium. The dry bulb mite (Aceria tulipae) is an eriophyid mite that survives on cultivated Allium species. Bulb mite species in the genus Rhizoglyphus can also be troublesome on alliums. Bulb mites overwinter in soil on debris, stored onions and garlic, and in garlic seed pieces. They are moved from field to field with soil on equipment, boots, etc., and planting infested garlic They are particularly troublesome in storage, causing desiccation and creating wounds that allow for entry of pathogens.
Bulb mites are favored by mechanical injury, disease, cool soil temperatures, and soils with high organic matter content. Avoid adding manure and use fallow periods to eliminate crop residue. In smaller plantings, removing culls from the field immediately after harvest will reduce overwintering populations. Dark plastic mulch will increase soil temperatures and control mites. Plant clean seed and rotate out of alliums for at least four years after an infestation. Avoid planting alliums directly after brassicas, corn, grain, or grass cover crops.
Caterpillars hide under the soil surface adjacent to the plant during the day and feed on leaves after dark. For best results, make application between midnight and dawn while cutworms are feeding aboveground. Synthetic pyrethroids may work best during cool spring weather. All synthetic pyrethroid restricted use (*) insecticides listed to control thrips on onions are also registered to control cutworm on this crop. See cutworms in the Pepper and Tomato (Outdoor) sections for more information on the black and variegated cutworms.
Bacillus thuringiensis aizawai (XenTariOG): 0.5 to 1.5 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested; apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt kurstaki products (Dipel).
Bacillus thuringiensis kurstaki (Dipel DFOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested; apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt aizawai products (XenTari).
Burkholderia spp. strain A396 cells and spent fermentation media (Venerate XCOG): 1 to 8 qt/A; PHI 0d, REI 4h, Bee: M.
Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M.
gamma-cyhalothrin (Declare*): .077 to 1.28 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.
lambda-cyhalothrin (Warrior* II): 0.96 to 1.60 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.
methomyl (Lannate* LV): 3 pt/A; PHI 7d, REI 48h, Bee: H, Group 1A. For green and dry onions. Add wetting agent to improve coverage. For black and variegated cutworm only.
spinosad (SeduceOG): 20 to 44 lb/A or 0.5 to1 lb/1000 sq ft.; PHI 1d, REI 4h, Bee: M, Group 5. Spread bait on soil around plants.
zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.
Onion Maggot (Delia antiqua)
Infestations may reduce young plant stands, cause plants to wilt and yellow, or damage bulbs. There are 3 generations each year. Effective control of the first generation (mid-May to June), which causes the most destruction, and minimizing mechanical and chemical damage to onions throughout the season, will reduce or eliminate damage by later generations. Rotate crops to keep maggot populations low; greater distances are more effective. Cumulative growing degree days (GDD) can be used to monitor the activity of onion maggot fly in your area: peak flight for the first generation is at 735 GDD, base 40°F. Delay planting until after first flight is finished and soil temperatures are high enough to kill eggs (95°F). Planting in late-May is more likely to be safer than the first half of May. Cover recently seeded or transplanted crops with floating row covers as a barrier against cabbage root maggot flies, placing the cover as soon as the transplants are set. Gathering culls into deep piles will limit reproduction to surface layers and reduce populations more than deep plowing or harrowing after harvest. Biological controls, including naturally-occurring fungal diseases, predaceous ground beetles, and soil applications of the entomopathogenic nematode Steinernema feltiae can all reduce onion maggot numbers. Nematodes can be applied to transplants, in transplant water, or as a post-transplant drench. Rates of 100,000 to 125,000 infective juveniles per transplant have been shown to be needed to achieve reduction in damage. Nematodes need a moist soil environment to survive. If using an insecticide, soil drench applications targeting the seed furrow or base of transplants, using at least 100-200 gal of water per acre to help the insecticide penetrate the root zone are the most effective.
chlorpyrifos (Lorsban 4E): 32 oz/A at-plant or 1 quart/A postplant soil drench; PHI 60d, REI 24h, Bee: H, Group 1B. For direct seeded onions, apply as band over row at planting in a minimum of 40 gal/A; for seedlings or transplants, apply at base of plants during peak egg laying time in a minimum of 100 gal/A. Dry bulb onions only. DO NOT make more than 2 applications per year (at-plant plus post-plant).
diazinon (Diazinon* AG500): 2 to 4 qt/A; REI 3d, Bee: H, Group 1B. Broadcast and incorporate just before planting. Will not control organophosphate-resistant onion maggots. For bulb and green onions. DO NOT make more than one application per year.
Onion Thrips (Thrips tabaci)
Onion thrips range in color from yellow to black and are only 1/16" in length. They spend the winter as adults in crop remnants, alfalfa, wheat, greenhouses and weeds along the border of crop fields. Thrips have rasping mouth parts which they use to tear open plant cells and feed on inner juices. Feeding occurs in protected areas between leaves. Damage may appear as silver lines, white patches, tip dieback and curling, slowed growth, reduced bulb size and yields, or result in plant death. Populations are favored by hot, dry weather. Plants are most sensitive when bulbs are forming and still small. Heavy rain or overhead irrigation can lower populations quickly. Lacewing larvae, pirate bugs and predatory thrips are important natural enemies. Reduce populations by cleaning up crop residue after harvest to limit overwinter sites. Do not plant onions near alfalfa, clover, cucurbits or brassica crops that can harbor large populations of thrips, which may migrate to onions when these crops are cut or harvested.
Scout plants along field margins where infestations build early. Begin applications when damage is first noticed or when there are 3 or more thrips per leaf. Repeat applications at 7- to 10-day intervals. From 3 to 6 applications may be necessary, but rotate between insecticide groups after 2 applications to help prevent resistance. Use a shorter interval in hot weather. Use spreader-sticker for better coverage. Apply in early evening, using high pressure and 100 gal water/A for best results.
acetamiprid (Assail 30SG): 5 to 8 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.
Beauveria bassiana (Mycotrol ESO): 0.25 qt to 1 qt/A; PHI 0d, REI 4h, Bee: L, Group 22. Treat when populations are low and thoroughly cover foliage. Takes 7 to 10 days after the first spray to see control. Repeat applications may be needed.
Burkholderia spp. strain A396 cells and spent fermentation media (Venerate XCOG): 1 to 8 qt/A; PHI 0d, REI 4h, Bee: M. Suppression only.
Chenopodium extract (Requiem EC): 1.5 to 3 qts/A; PHI 0d, REI 4h, Bee: L. Begin application as soon as thrips are seen. Thoroughly cover foliage.
Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M.
cyantraniliprole (Exirel): 13.5 to 20.5 oz/A; PHI 1d, REI 12h, Bee: H, Group 28. Suppression only.
deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.
gamma-cyhalothrin (Declare*): .1.02 to 1.54 oz/A; PHI 1d, REI 24h, Bee: H, Group 3A.
imidacloprid (Admire Pro): 14 oz/A; PHI 21d, REI 12h, Bee: H, Group 4A. Soil applications only.
kaolin (Surround WPOG): 25 to 50 lb/A or 0.25 to 0.5 lb/gal; PHI 0d, REI 4h, Bee: L. Suppression/repellence only. Good coverage into plant crown is essential. Generally compatible as a tank mix with other insecticides.
lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.
malathion (Malathion 57EC): 1.5 pt/A; PHI 3d, REI 12h, Bee: H, Group 1B.
Metarhizium anisopliae Strain F52 (Met 52 EC): 40 to 80 oz/100 gal (drench), 8 to 64 oz/A (foliar); PHI 0d, REI 0h, Bee: L.
methomyl (Lannate* LV): 3 pt/A; PHI 7d, REI 48h, Bee: H, Group 1A. For green and dry onions. Add wetting agent to improve coverage. Begin application before populations reach 3 to 5 thrips per plant.
permethrin (Pounce* 25WP): 9.6 to 19.2 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. For dry bulb onions only
petroleum oil (Suffoil XOG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L. Apply as needed.
pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.
pyriproxyfen (Esteem 0.86EC): 8 oz/A; PHI 3d, REI 12h, Bee: L, Group 7D. Dry bulb onions only. Suppression only.
sodium tetraborohydrate decahydrate (Prev-AM): 100 oz/100 gal; REI 12h, Bee: L, Group 25. Do not apply in midday sun or mix with copper, sulfur or oils.
spinosad (Entrust SCOG): 4 to 8 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Suppression only. Use adjuvant for better control.
spinetoram (Radiant SC): 6 to 10 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Thorough coverage is essential. Efficacy improves with the addition of an adjuvant.
spirotetramat (Movento): 5 oz/A; PHI 3d, REI 24h, Bee: M, Group 23. Must be tank-mixed with a spray adjuvant with spreading and penetrating properties to maximize leaf uptake and sytemicity; don't use sticker adjuvants. Controls immature stages; may also reduce adult fertility.
zeta-cypermethrin (Mustang*): 3.2 to 4.3 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.