Pest description and crop damage Adults are small gray, tan, or off-white moths that have a hairy appearance. Female moths have a much reduced wing size and are flightless. Larvae, up to 12 mm long, are pale green with white, longitudinal stripes along the abdomen. The larvae move by "inching" along, hence the nickname "inchworm." Larvae damage buds, blooms, leaves, and fruit from March to mid-summer. Symptoms of leaf feeding are distinct from leafroller larvae: leaves are tied together with silken threads, but not rolled like a leafroller.
Biology and life history This insect pupates in the soil in summer and fall; adults emerge in late fall and early winter (hence the name "winter moth"). After emergence, the flightless female mates, crawls up the canes, and deposits eggs in bud or cane crevices. Larvae hatch in early spring and immediately begin feeding on developing buds. After feeding for several weeks, larvae drop to the soil on silken threads and pupate until fall. Adults emerge after the first frost. There is one generation per year.
Sampling and thresholds Monitor fields in early spring for larvae, larval webbing, and feeding on buds. Also, in early morning and early evening, silken webs may be seen in the slanting sunlight (young larvae climb out to an open branch and send out a fine, silken web for dispersion by wind to find new food sources). A treatment application may be necessary if there are more than eight larvae per plant.
Management-chemical control: HOME USE
There are no products registered for control of this pest.
Management-chemical control: COMMERCIAL USE
- Bacillus thuringiensis (Bt) (several brands)-Consult label for rate. PHI 0 days. Some formulations are OMRI-listed for organic use.
- chlorantraniliprole (Altacor) at 0.066 to 0.1 lb ai/a. PHI 3 days. Do not exceed 0.2 lb ai/a per crop season.
- diazinon (several brands) at 0.5 to 1 lb ai/a. PHI 7 days. One application per season allowed; as such, consider other pests that may need to be managed with diazinon.
- methoxyfenozide (Intrepid 2F) at 0.25 lb ai/a. PHI 3 days. Begin applications at first egg hatch or to young larvae when infestations are detected.
- spinetoram (Delegate WG) at 0.05 to 0.09 lb ai/a. PHI 1 day.
- spinosad (Success or Entrust) at 0.062 to 0.1 lb ai/a. PHI 1 day. Apply at egg hatching or to small larvae. Entrust is OMRI-listed for organic use.
- zeta-cypermethrin (Mustang) at 0.05 lb ai/a. PHI 1 day.