Corn earworm present at high density

As reported in VegNet last week, the corn earworm population is on the increase in Ohio. At our research farm in Columbus, there were 60 corn earworm moths caught in our pheromone trap during the previous week (13-19 August), and this increased to 577 moths caught in the week that is now ending (20-26 August). Sixty moths in one week is considered to be moderate pest pressure, while 500 moths in one week is considered to be very high pest pressure. Sweet corn that is in the silking stage is at risk of infestation by corn earworm larvae unless it is sprayed with insecticide every 3 days. Details about spray intervals based on trapping can be found at: . Beware that when earworm moths are abundant, control by pyrethroid insecticides (Warrior, Mustang Maxx, Baythroid, Asana, Permethrin, Brigade) has tended to be fair to poor during the past few years due to the development of resistance. Alternative insecticides are Coragen, Radiant, Blackhawk, and Lannate. Entrust is a good option for organic production.

Sweet corn that is genetically engineered to produce the B.t. toxin, as in the Attribute and Attribute II hybrids from Syngenta, and the Performance hybrids from Seminis, offer some protection from infestation by earworm and other caterpillars. These B.t. hybrids were excellent for caterpillar control when first introduced, but in the past few years, hybrids in the Attribute and Performance series are showing only moderate protection from earworm if not supplemented by insecticide sprays, whereas the Attribute II hybrids are still showing excellent control of earworm and other species. A supplemental insecticide spray can be applied when 75-100% of plants have fresh silk, which is a few days later than the typical first spray on non-BT corn.

Weekly catch of corn earworm at several sites is shown on our online Ohio trap report page: , where there is a tab for this species and several other pests along the bottom of the sheet.


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