Integrated Crop Management

Corn insect scouting calendar for 2001

Knowing when to scout for potential corn pests is one of the key components to a successful pest management program. Many insect pests occur in corn across Iowa, but not all of them develop economically damaging populations. Most problems occur when corn is still young and the plant stand is more likely to suffer serious injury. This scouting calendar will help you focus your efforts on what insects to watch for during specific corn growth stages. Refer to current or past issues of the ICM newsletter for information on economic thresholds and treatment recommendations.

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; also in fields after pasture
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 Populations higher in central and southern Iowa
Emergence and

early whorl
VE-V3 hop vine borer May through

early June
Found on lighter soils in NE quarter of Iowa (north and east of Marshalltown)
Emergence and

early whorl
VE-V5 billbug May through early June Found on low ground, often associated with yellow nutsedge
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 through early June Uncommon; mostly likely in fields planted no till into weeds
Emergence and

early whorl
VE-V5 chinch bug May throughearly June Uncommon; mostly in extreme SW Iowa following a dry summer
Early whorl V1-V6 stalk borer Late May through June;

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 weed-free fields, larvae will move from brome terraces and ditches into adjacent corn rows
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, or fields with rye cover crop
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 (base 50°F)

after first moth flight
Most common in earliest planted fields
Tassel VT western bean cutworm July through early August Uncommon but found in western Iowa (north and west of Carroll), see ICM newsletter for scouting dates
Early tassel VT corn leaf aphid July through early August Uncommon but found across the state
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 Most common in continuous corn

This article originally appeared on pages 64-65 of the IC-486 (8) -- May 7, 2001 issue.


Source URL:
http://www.ipm.iastate.edu/ipm/icm//ipm/icm/2001/5-7-2001/scoutcalendar.html