Potential of Corn Rootworm (Coleoptera: Chrysomelidae) Larval Counts to Estimate Larval Populations to Make Control Decisions

A corn root worm larval sampling technique was evaluated for 5 years in eastern Nebraska. The percentage of larvae of Diabrotica</it> spp. detected in field samples by an experienced scout ranged from 3 to 6% for 1st instars, 6 to 18% for 2nd instars, and 18 to 21% for 3rd instars. High correlations were found between field and absolute counts for all 5 years. Scout experience apparently influenced the number of larvae detected in the field. The number of days from hatch until the first larva was detected in the field ranged from 3 to 11 days. The time frame from field detection to potentially serious root damage is apparently too small for this technique to be used to make control decisions to minimize damage. However, it may be of some value in making emergency treatment recommendations.