The foundation of an insect management program includes timely field scouting and knowing how and when to make insect-control decisions, based on insect numbers or plant damage, or both.

Cultural control
1. Cultural control
  - crop rotation
  - tillage operations
  - timing of planting and harvesting activities
2. Biological control
3. Insect resistant crops
  - conventional plant breeding
  - biotechnology
4. Insecticides
  - Decision to use an insecticide should be based on:
    - information from crop scouting
    - understanding of economic thresholds
    - knowledge about the potential for the occurrence of insect pests
  - Soil-applied insecticides
  - Foliar-applied insecticides

Economic threshold (Action threshold): The pest density or level of damage at which a control measure is needed to prevent economic loss.

Economic thresholds are not static; they change with fluctuating market values or control costs

If the value of corn or soybean increases, the economic threshold declines
If the cost of control increases, the economic threshold increases.

Economic loss: Occurs when the cost of insect damage in terms of yield or quality exceeds the cost of control.

Insect Groups

Below ground insects
Above ground insects
Stored grain insects
Occasional insect pests

Gallery of Corn Insects Clemson University

Often more of a problem than corn diseases in the Midwest

Basic Plan for Scouting Corn in the Corn Belt

Shortly after crop emergence: early season insects like cutworms, white grubs, wireworms
mid-June: first generation European corn borer
July: corn rootworm adults and corn leaf aphids
late-July and early August: second generation European corn borer

Scouting calendar for corn insects

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
emergence and early whorl	VE-V3	hop vine borer	May through early June	found on lighter soils
emergence and early whorl	VE-V5	black cutworm	300 degree days (base 50 F) after significant moth flight; often mid-May to early June
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 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

Below ground Insects

Wireworms and Cutworms - are a problem early in the season

Corn rootworms - major problem in Midwest

Western corn rootworm
Northern corn rootworm
Southern corn rootworm (cucumber beetle)
Damage - root pruning (larvae)
beetles cause silk damage
Many corn growers band corn rootworm insecticide at planting (Counter, Furadan, Lorsban, etc)

Above Ground Insects

European corn borer

Major Corn Belt problem
1st brood - leaf damage
2nd brood - Stalk breakage and ear drop
- Greater effect on yield

Corn earworm - damages the ear; usually not a major problem

Aphids - corn leaf aphid

Grasshoppers - Common problem in Western US

More prevalent in western half of Corn Belt

Fall armyworm

Flea beetle

Mites

Stored grain insects

Rice weevil - Most prevalent

Angoumois grain moth

Occasional insect pests

billbugs, chinch bugs, hop vine borer, sod webworm, southern corn leaf beetle, sugarcane beetle, western bean cutworm, white grubs

Corn Insects