Evaluation of corn hybrids for tolerance to corn rootworm (Diabrotica virgifera virgifera LeConte) larval feeding

The western corn rootworm (Diabrotica virgifera virgifera LeConte (WCR)) is a major pest of corn in USA. The pest arrived in Croatia in 1995, and today over 250.000 ha are infested. Insecticides are regularly used to control WCR, but the cost is high, can pose environmental risks, and may become ineffective due to resistance. Growing corn that is resistant to corn rootworms would be a valuable alternative to insecticides. Nine Croatian (Institute of Agriculture, Osijek) and two Pioneer Hi-Bred Int. Inc. (Johnston, Iowa, USA) commercial corn hybrids were evaluated for WCR resistance at two locations using complete randomized block design with four replications. One location was in east Croatia (Osijek) and one was in the USA (Iowa). The hybrids’ tolerance to larval feeding was rated using root injury, root regrowth and root size. Root injury was rated using the Node-Injury Scale 0–3 and evaluation of root size and root regrowth were done by scale 1–6. In an analysis of variance combined across locations, root injury didn’t show any significantly differences among hybrids, but root regrowth and root size were significantly different.