Predicting movement of stalk borer (Lepidoptera: Noctuidae) larvae in corn

Abstract

The stalk borer [ Papaipema nebris (Guenee)], is a sporadic, yet serious pest of corn, ( Zea mays L.), in the midwestern USA, particularly where corn fields are adjacent to grassy areas, such as roadside ditches, grass waterways, and terraces. An important management strategy is to apply an insecticide when the larvae move from the initial grass or broadleaf hosts to corn hosts. After the larvae bore into corn stalks, they are much more difficult to manage. Therefore, predicting the movement of larvae from weed hosts to corn hosts is crucial. This study was conducted to determine probable dates for stalk borer larval movement using climatic data from 67 locations across portions of South Dakota, Nebraska, Kansas, Minnesota, Iowa, Missouri, Wisconsin, Illinois, Michigan, and Indiana. We also examined the difference in probable dates of larval movement using the entire climate data record (60–90 yr) as opposed to using the 30-yr climatic normal record (1961–1990). The minimum number of degree-days (780 Celsius degree-days 4.4 °C base temperature) in which larvae move from initial weed hosts to corn, were accumulated for each year in the climate record beginning 1 March and correlated with calendar dates. The mean date of larval movement in the in the states examined spans approximately 3 weeks, from 2 June in the southern portions to 23 June in the northern portions. Standard deviations about the mean date of larval movement were 5, 6, and 7 days in the southern, central, and northern portions, respectively. There was little difference between predicted dates using long-term climatic data compared to those using 30-yr climatic normal data.