Beet webworm (Loxostege sticticalis)
Garden webworm (Achyra rantalis)
Pest description and crop damage Olive-green larvae up to 1.5 inches long, marked with black dots and both dark and light stripes down the back and along sides. If disturbed, larvae hang from leaves by silk threads.
Feeding initially appears as small transparent "windows" eaten from the undersides of leaves; later, it progresses to raggedly skeletonized and dirty, webbed leaves, especially midseason.
Scouting and thresholds No formal economic thresholds exist for webworm insecticide treatment decisions. Consider treatment if infestation levels average one to two webworm larvae on half the plants. Monitor infestations closely, because webworms can defoliate plants rapidly.
Management-biological control
- Beauveria bassiana (live spores of an insect-killing fungus; various strains)-See label for rates. PHI 0 days. Typically requires 7 to 10 days after first spray to see control. Begin treatment at first appearance of pest. Reapply as necessary.
- Bacillus thuringiensis aizawai (XenTari - live spores of an insect-killing bacterium)-See label for rates. PHI 0 days. Biological insecticide most effective against small, newly hatched larvae. No contact action; larvae must eat treated leaves. Use a spreader-sticker. Some formulations are OMRI-listed for organic use.
- Bacillus thuringiensis kurstaki (Biobit HP, Dipel DF, Javelin, and others - live spores of an insect-killing bacterium)-See label for rates. PHI 0 days. REI 4 hr. Biological insecticide most effective against small, newly hatched larvae. No contact action; larvae must eat treated leaves. Use a spreader-sticker. Some formulations are OMRI-listed for organic use.
- GS-omega/kappa-Hxtx-Hv1a (Spear LEP - peptide derived from spider venom)-See label for rates. Tank mix with Bacillus thuringiensis products (Bts) to enhance control. PHI 0 days
Management-chemical control
- azadirachtin-Some formulations are OMRI-listed for organic use.
- (Debug Trés) at 0.0375 to 0.1054 lb ai/A.
- azadirachtin/pyrethrins (Azera and Azera Pro) at 0.0125 to 0.025 lb ai/A, and up to 0.044 lb ai/A under extremely heavy infestation. Dilution in a minimum of 30 gal water per acre is recommended for conventional equipment. May be applied by air at the rate of 0.0125 to 0.025 lb ai/A in a minimum of 25 gal water. Do not repeat more than every 5 to 7 days. OMRI-listed for organic use.
- carbaryl (Carbaryl 4L, Sevin 4F, Sevin XLR Plus, and others) at 1 to 1.5 lb ai/A. PHI 28 days. For Carbaryl 4L, Sevin 4F, and Sevin XLR Plus, do not apply more than a total of 3 lb ai/A per crop.
- esfenvalerate (Asana XL, S-fenvaloStar, Zyrate) at 0.03 to 0.05 lb ai/A. PHI 21 days. Apply as necessary but no more than 0.15 lb ai/A per season. Apply with ground or air equipment using enough water (at least 2 gal/A) to cover uniformly.
- methomyl (Annihilate LV, Annihilate SP, Lannate LV, Lannate SP, M1 LV, M1 SP, Nudrin LV, Nudrin SP) at 0.225 to 0.9 lb ai/A. PHI for roots 21 days or 30 days if tops are fed to livestock. REI 48 hr. Do not apply more than 4.5 lb ai/A per crop or apply more than 10 times per crop.
- methoxyfenozide (Inspirato 2F, Intrepid 2F, Invertid 2F, Troubadour, Vexer, Withstand, Zylo) at 0.12 to 0.25 lb ai/A. Apply at egg hatch or when signs of feeding occur. PHI 7 days.
- methoxyfenozide/spinetoram (Intrepid Edge) at 0.11 to 0.28 lb ai/A. Apply at egg hatch or first signs of feeding. PHI 7 days.
- neem oil (Terraneem EC)-See label for rates. OMRI-listed for organic use.
- pyrethrins (Lynx EC 1.4, Lynx EC 5.0, PyGanic EC 1.4, Tersus)-See label for rates. REI 12 hr. PHI 0 days. Some formulations are OMRI-listed for organic use.
- pyrethrins/Beauveria bassiana (BotaniGard Maxx, Xpectro OD)-See label for rates. Do not reapply for at least 3 days. In case of extreme pest pressure, wait a minimum of 24 hr before reapplying. Do not harvest until spray has dried.
- pyrethrins and piperonyl butoxide (Evergreen Crop Protection EC 60-6, Pyrenone, Pyronyl Crop Spray, and others)-See label for rates.
- zeta-cypermethrin-
- (Mustang) at 0.028 to 0.05 lb ai/A. PHI 50 days. Do not apply more than 0.15 lb ai/A per season (at planting/foliar applications). Apply with ground or air equipment with enough water to fully cover foliage.
- (Mustang Maxx) at 0.014 to 0.025 lb ai/A. PHI 50 days for tops or roots. Do not apply more than 0.075 lb ai/A per season. REI 12 hr. Apply by air or ground using minimum of 2 gal per acre by air and 10 gal per acre by ground.