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 [1] 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 [2] 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.
