Southwestern corn borer (Lepidoptera: Crambidae) dynamics on the Texas High Plains

Southwestern corn borer, Diatraea grandiosella Dyar, bores into the stalk and damages ears of maize, Zea mays L., in the southwestern U.S. Although chemical and cultural controls are used on the Texas High Plains, expanded acreage, nondisturbed fields, and favorable environmental conditions favor establishment of annual infestation by this insect pest. Understanding factors that influence severity and abundance of pests is essential in integrated pest management because insect phenology is impacted annually by dynamic interacting elements, especially environment. A model that predicts the occurrence of southwestern corn borer based on field data and temperature is necessary for efficient monitoring and management. Southwestern corn borer adults from three irrigated maize and two non-maize habitats on the Texas High Plains were collected in pheromone-baited traps each week from May-October 2008 and 2009. Weather data were obtained from the NOAA-National Climatic Data Center. Southwestern corn borer had two distinct periods of moth activity and a small overwintering flight as temperature warmed in the spring of 2008 and 2009. Most adults from the first generation emerged between late June and early July when average temperatures were approximately 23 and 24oC. More than 50% of the moths of the second generation were captured in mid-August. Significantly more moths were caught in commercial fields than in grassy areas with no maize nearby. Differences in numbers of adults trapped among locations can be attributed to the presence or absence of maize stubble, agricultural practices, variation in daily temperature, and extreme weather events.