Effects of adult western corn rootworm (Diabrotica virgifera virgifera LeConte, Coleoptera: Chrysomelidae) silk feeding on yield parameters of sweet maize

The western corn rootworm [Diabrotica virgifera virgifera LeConte (WCR)] is an economic pest of maize in North America and in most maize growing regions in Europe. Although the maize root-feeding larval stage causes the primary damage, yield losses due to WCR adult silk clipping on maize ears can occur in inbred lines and commercial grain maize, for which WCR economic thresholds have been determined in North America and Central Europe. However, similar data for sweet maize are not available. The aim of this research was to determine if silk feeding damage in sweet maize resulted in production losses and, if so, at what WCR adult levels. The three-year study was conducted using the Suregold sweet maize variety in Hungary from 2016 to 2018. Nylon bridal veil cages were placed over maize ears at the beginning of R1 plant stage with 0, 1, 2, 4 or 8 beetles in 2016 and 0, 1, 2, 4, 8 or 12 beetles in 2017 and 2018 placed inside the cages. Uncaged ears were used as untreated controls. Silk length was measured daily until the end of silking. Adults were then removed from the cages, but the cages remained covering the ears until harvest. After harvest, cob weights were determined and fertility ratios were assessed. The three-year results showed that WCR densities of up to 8 adults/ear are not likely to lead to economic damage in sweet maize.