D3138: Efficacy of insecticides applied through chemigation for western corn rootworm (Diabrotica virgifera virgifera LeConte) and other maize pests

The western corn rootworm (WCR) Diabrotica virgifera virgifera, is native to North America and is recognized as an economically important pest of continuous maize. Larvae feed belowground on maize roots, while adult beetles feed on silks and ear tips, which may inhibit pollination. Adult control is complicated due to the prolonged emergence of beetles, insect migration, treatment timing, and insecticide resistance. Most applications targeting ear-feeding pests are done by aerial spraying, however, some growers apply pesticides utilizing the center irrigation pivot, known as chemigation. Pyrethroids are a common insecticide mode of action used in the control of adult beetles, however, resistance has been documented in Nebraska. Diamides are increasingly used to target lepidopteran pests, but rootworm beetles are in the field at the same time. The objective of this project is to evaluate the efficiency of chemigation in controlling WCR beetles and other ear-feeding pests in maize. The WCR population abundance, percentage of injured ears, type of injury (categorizing injury type to each pest) and evaluation of potential yield loss were assessed. Bifenthrin and chlorantraniliprole were applied via center pivot irrigation at its highest (6.4 and 20 fl oz/ac, respectively) and lowest (2.1 and 14 fl oz/ac) label rates, using two water-carrying volumes (0.25 and 0.75 acre-inches). This project evaluated the viability of chemigation as an application method to control adult beetles and other important maize pests. Moreover, results from this study can provide evidence to help reduce production and application costs in maize by adopting chemigation methods.