Evaluation of Serbian commercial corn hybrid tolerance to feeding by larval western corn rootworm (Diabrotica virgifera virgifera Leconte) using the novel difference approach

Since the discovery of the pest in 1992, western corn rootworm (Diabrotica virgifera virgifera LeConte (WCR)) populations in Serbia have successfully been kept low with crop rotation. This has reduced the efficiency of screening maize for WCR resistance. A coop- erative project between Iowa State University and the Maize Research Institute, Zemun Polje evaluated 13 Ser- bian commercial maize varieties in Ames, Iowa over a two-year period using the difference approach. Maize hy- brids were planted on trap crops where high WCR popu- lations were assumed. Hybrids were evaluated for WCR resistance using a randomized complete block design with four replications. Treatments were paired-rows arranged in split plots with one row in each pair treated with insecticide and the other row left untreated. WCR in- jury was evaluated using a rating of root size and root re- growth (1-6 scale), root injury (0-3 Node-Injury Scale), root mass, lodging, and yield. The results indicated signif- icant differences among the Serbian hybrids in the pres- ence of moderate-to-high levels of western corn root- worms. The relative benefit of insecticide treatments for maize hybrids was a useful tool in evaluating resistant germplasm. However, conducting analyses on relative dif- ferences between insecticide treated and untreated plots was not as effective at detecting differences as comparing the plots independently.