Scouting calendar for corn insects

by Marlin Rice, extension entomologist, Department of Entomology

Corn growth

Corn stage

Insect

Calendar

Comments
preemergence seed-VE seedcorn maggot May most common during cool, wet spring or in fields with animal manure or recent green vegetation
emergence and early whorl VE-V3 true white grub May most common in areas adjacent to willow and cottonwood trees
emergence and early whorl VE-V3 wireworm May most common following pasture or CRP grasses
emergence and early whorl VE-V3 corn flea beetle May see ICM newsletter for areas in state with high probability
emergence and early whorl VE-V3 hop vine borer May through early June found on lighter soils in NE quarter of Iowa
emergence and early whorl VE-V5 black cutworm 300 degree days (base 50 F) after significant moth flight; often mid-May to early June see ICM newsletter for scouting dates
emergence and early whorl VE-V5 stink bug May uncommon; mostly likely in weedy fields
emergence and early whorl VE-V5 chinch bug May uncommon; mostly in SW Iowa following dry summer
early whorl V1-V6 stalk borer late May through June; egg hatch (575-750 degree days base 41 F); begin migration from grass (1300-1400 degree days base 41 F) most common in fields with grassy weeds or giant ragweed; in clean fields, larvae will migrate from brome terraces and ditches
mid-whorl V6-V10 corn rootworm larva early to mid-June mostly in continuous corn
mid-whorl V6-V10 armyworm late May to early July most common following no-till sod or in fields with grassy weeds, such as foxtail
mid- to late-whorl V8-V14 European corn borer (first generation) June through early July; begin when corn reaches "knee height" or 200 degree days (basse 50 F) after first moth flight most common in earliest planted fields
tassel VT corn leaf aphid July through August  
tassel to milk stage VT-R3 grasshoppers July through early September most common along field margins and grassy areas
silk R1-R2 European corn borer late July through August most common in latest planted fields
silk R1-R2 corn rootworm adult late July through August  

This article originally appeared on page 64 of the IC-482(10) -- May 17, 1999 issue.

Updated 05/16/1999 - 1:00pm