A field study of western corn rootworm/drought interactions with maize hybrids exhibiting various drought and rootworm tolerance

The effects of soil moisture on the interaction between maize and western corn rootworm are understudied for a pest of this magnitude. In 2012, a field study was conducted to evaluate the interactions of the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte and drought stress on maize. The experiment was a randomized complete block design combining five maize lines;  B73×Mo17, Pioneer’s Bt (Cry34/35Ab1) + AQUAmax drought-tolerant maize, AQUAmax alone, Bt alone, and the Bt isoline; in well-watered and drought stressed soil (achieved with a rainout shelter), under a moderate and zero western corn rootworm infestation. WCR infestation significantly impacted yield, but much less than the effect of drought. Under combined drought and rootworm pressure, the Bt + AQUAmax hybrid was significantly less water-stressed than the hybrid with Bt alone, and the yield of the Bt + AQUAmax hybrid was significantly higher than with the other maize pedigrees. Root complexity and root dry weight were also highest for the Bt + AQUAmax hybrid. Rootworm damage was not significantly impacted by moisture or its interactions with maize pedigree. These results indicate that the effect of drought on maize performance is much greater than the effect of WCR. The combination of AQUAmax and Bt resulted in a decreased effect of these stresses on maize performance. Overall, these results indicate that the effect of drought on maize performance is much greater than the effect of WCR. Data from 2013 will also be included.