| Onion - Insect Control |
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Insect ControlNOTE: For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 20 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients. CutwormsCaterpillars 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 (XenTari): 0.5 to 1.5 lb/A (0 dh, REI 4h, Group 11). Must be ingested; apply in evening before larvae are actively feeding and direct sprays to base of stem. Use high rate at cool temperatures. OMRI listed. lambda-cyhalothrin (Warrior*): 2.5 to 3.8 oz/A (14 dh, REI 24h, Group 3A). methomyl (Lannate* LV): 3 pt/A (7 dh, REI 48h, Group 1A). For green and dry onions. Add wetting agent to improve coverage. For black and variegated cutworm only. zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A (7 dh, REI 12h, Group 3A). Onion MaggotInfestations may reduce young plant stands, cause plants to wilt and yellow or damage bulbs. There are three generations each year. Effective control of the first generation (mid-May-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. Harvesting with a potato digger causes less damage than undercutting onions. In smaller plantings, removing culls from the field immediately after harvest will reduce overwintering populations. Gathering culls into deep piles will limit reproduction to surface layers and reduce populations more than deep plowing or harrowing after harvest. If harrowing after harvest, wait until frost to limit bulb damage and winter survival. Granular or soil drench insecticide applications are the most effective. Soil Application: cyromazine (Trigard OMC): (60 dh, Group 17). Seed treatment for onion maggot control. Treated seed must be purchased. See rotational crop restrictions on label. diazinon (Diazinon* AG500): 2 to 4 qt/A broadcast and incorporate just before planting (7 dh, REI 24h, Group 1B). Will not control organophosphate resistant onion maggots. Foliar Application for adult flies: gamma-cyhalothrin (Proaxis*): 1.9 to 3.2 oz/A (14 dh, REI 24h, Group 3A). Adults only. lambda-cyhalothrin (Warrior*): 1.9 to 3.2 oz/A (14 dh, REI 24h, Group 3A). Adults only. malathion (Malathion 57EC): 2 1/2 to 3 pt/A (3 dh, REI 12h, Group 1B). permethrin (Pounce* 25WP): 6.4 to 19.2 oz/A (1 dh, REI 12h, Group 3A). For dry bulb onions only. zeta-cypermethrin (Mustang*): 2.4 to 4.3 oz/A (7 dh, REI 12h, Group 3A). Onion ThripsOnion 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. Beauveria bassiana (Mycotrol O): 8 to 32 oz/A (0 dh, REI 4h, Group 22). Thoroughly cover foliage. Takes 7 to 10 days after application to see control. OMRI listed. pyrethrin (PyGanic EC5.0): 4.5 to 18 oz/A (0 dh, REI 12h, Group 3A). OMRI listed. spinetoram (Radiant SC): 6 to 10 oz/A (1 dh, REI 4h,Group 5). spinosad (SpinTor 2SC): 4 to 8 oz/A (1 dh, REI 4h, Group 5). Suppression only. zeta-cypermethrin (Fury* 1.5EC): 3.2 to 4.2 oz/A (7 dh, REI 12h, Group 3A). Begin applications when pest first appears. See restrictions on label. MitesBulb mites are favored by mechanical injury, disease, cool soil temperatures, and soils with high organic matter content. Control onion diseases, 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. |
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