Project Number: 3622-21220-007-09
Project Type: Specific Cooperative Agreement

Start Date: Feb 01, 2013
End Date: Jan 31, 2014

Objective:
1) To determine if differences in behavior between Bt resistant and Bt susceptible western corn rootworm larvae exist. 2) To determine if there is behavioral resistance to Bt in corn by evaluating a “martyr” hypothesis.

Approach:
Previous research has shown that larvae of the WCR tend to show a non-preference towards feeding on the roots of Bt plants. Root scans of Bt plants indicate that the Bt proteins tend to “clump” in the plant root and form greater concentrations near the root tips. It is possible that rootworm larvae are able to detect the presence of Bt protein in the roots and actively avoid feeding on areas of high concentration thus circumventing the insecticidal properties of the plant. If this is the case there should be some difference in the feeding behavior between susceptible and Bt resistant WCR larval feeding. We will be evaluating behavior of WCR larvae resistant and susceptible to Bt in response to differing corn traits. Another observation of possible behavioral resistance to Bt involved a “martyr” hypothesis. Previous workers observed larval feeding on Bt corn plants in which 99% of the first introduced larvae died within 2 days. Three days later researchers added more larvae to the plants at which point 8% of the larvae survived. Three days after that another group of larvae were placed on the plant at which point 21% survived. The larvae were reported as visiting the same feeding locations as previous larvae. Researchers theorized that the previous feeding caused by the dead larvae had opened up pathways past the higher Bt concentrations in the root and thus allowed the later larvae to avoid it. We will conduct a series of studies to evaluate this hypothesis.