There are two species of corn rootworm:  

• Western corn rootworm (orange black) and Northern corn rootworm (Green).  Most of the problems are caused by Western corn rootworm.

• However, in the northern parts of the US, Northern corn rootworm can be problematic.

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In almost all cases, CRW lays its eggs in existing corn fields during August.

• When area populations are high, CRW females have been recorded to lay eggs in grain sorghum (milo) fields.  

• Each female lays about 300 eggs, often in concentrated patches. Therefore, crop rotation to a non-corn crop is a viable way to reduce CRW problems.  

• Usually, 1^styear corn following a non-corn crop does not require any CRW management tools(RW traited corn or soil insecticide).

• Exception #1 - In Eastern Iowa, Illinois, Indiana, and most of Ohio, there is a strain of Western corn rootworm which lays in soybeans and when corn follows soybeans, there can be CRW root damage in 1^st year corn.  

• Exception #2 - Northern corn rootworm has some eggs which hatch the following spring, some eggs which hatch in year 2 and sometimes eggs that hatch in year 3. This is called extended egg diapause. Corn growers in these areas often have to use RW management tools in 1^st year corn.

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Generally, the RW egg hatching period is last week of May through the 1^st week of June.

• Planting corn after June 1 seldom requires RW management since most of the newly hatched larvae die due to lack of roots.  Field capacity soils (excess water) during this time period also kills a lot of these larvae from lack of oxygen.

• Larval root feeding is completed by corn pollination.  This is the best time to dig, wash and evaluate roots for root feeding.

• Delaying the root digging allows the roots to start regenerating, making the damage harder to see.

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Adult emergence usually begins about a week before tassel emergence and the first emerging beetles are males.  

• Adult emergence usually begins about a week before tassel emergence and the first emerging beetles are males.  

• Females start emerging 10-14 days later.  Females need to feed on pollen sources for about 3 weeks before they start laying eggs in existing corn fields.

• Adults are mobile and move from field to field in search of corn pollen as a required food source.