Sugar beet-Webworm

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 (BotaniGard Maxx - live spores of an insect-killing fungus)-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.

Management-chemical control

  • azadirachtin-Some formulations are OMRI-listed for organic use.
    • (Azatin O) at 0.025 to 0.1 lb ai/a. Foliar application against larvae.
    • (Debug Tres) at 0.0375 to 0.1054 lb ai/a.
  • azadirachtin + pyrethrins (Azera) 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 of 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 of water. Do not repeat more than every 5-7 days. OMRI-listed for organic use.
  • carbaryl (Carbaryl 4L, Sevin 4F, Sevin XLR Plus, Sevin RP4, Sevin 80 Solupak, 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. For Sevin RP4, do not apply more than a total of 4 lb ai/a per crop. For Sevin 80 Solupak, do not apply more than 4 lb ai/a per crop.
  • chlorpyrifos (Eraser, Govern 4E, Lorsban 4E, Lorsban 75WG, Nufos 4E, Pilot 4E, Warhawk, Whirlwind, Yuma 4E,and others) at 0.5 to 1 lb ai/a broadcast, or 0.335 to 0.67 lb ai/a band application. PHI 30 days. Do not let livestock graze in treated areas or harvest treated beet tops as feed for meat or dairy animals within 30 days after last treatment. Apply band application as 5- to 7-inch spray; lightly incorporate mechanically or with irrigation. Do not apply more than 2 lb ai/a of the 75WG formulation per season or more than 3 lb ai/a of the 4E formulation per season. Do not apply chlorpyrifos more than three times per season.
  • chlorpyrifos (Lorsban Advanced, Vulcan) at 0.469 to 0.939 lb ai/a broadcast, or 0.313 to 0.626 lb ai/a band application. PHI 30 days. Do not let livestock graze in treated areas or harvest treated beet tops as feed for meat or dairy animals within 30 days after last treatment. Apply band application as 5- to 7-inch spray; lightly incorporate mechanically or with irrigation. Do not apply more than 2 lb ai/a of the 75WG formulation per season or more than 3 lb ai/a of the 4E formulation per season. Do not apply chlorpyrifos more than three times per season.
  • 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, Corrida 29 SL, Corrida 90 WSP, Lannate LV, Lannate SP, Lemur, 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 (Intrepid 2F, Troubadour) at 0.12 to 0.25 lb ai/a. Apply at egg hatch or when signs of feeding occur. PHI 7 days.
  • 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 (Xpectro OD)-See label for rates. Do not exceed 0.05 lb ai/a. 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.