Deviation from Typical CRW Behavior

Extended diapause

Extended diapause is associated with the northern corn rootworm. This phenomenon describes the NCR beetles that have adapted to the corn-soybean management option practiced for years by farmers.  Normally diapause, or the hibernation period, lasts only until the next season.  With extended diapause, the eggs laid in the soil by NCR females remain in the soil for two or more years and hatch when a farmer rotates back to corn. Extended diapause is present in Minnesota, Iowa, South Dakota, North Dakota, and Nebraska. (FIG. 9)

Fig. 9:  Extended Diapause distribution (UNL)

Soybean variant

The soybean variant refers to WCR females that have adapted to laying their eggs in soybean fields.  The females have trouble living in soybean fields, but derive enough nutrients to be successful with laying eggs.  Previously, farmers used the corn-soybean rotation as a way to break the CRW cycle and avoid crop damage.  Now with the identification of soybean variant other control methods may need to be used.  This problem has been found to occur in Indiana, Illinois, Ohio, and Michigan.  (FIG. 10)

Fig. 10:  Soybean Variant distribution (UNL)