Abstract

Information on spatial and temporal dynamics of the lesser grain borer (LGB), Rhyzopertha dominica (F.), in agricultural landscapes is not adequate. This research was undertaken with the objective of determining the flight capacity, seasonal patterns and spatial distribution, and seasonal egg-development status in relation to flight. A mark-release-recapture study was undertaken on the Konza Prairie Biological Research Station, Kansas State University, Manhattan, Kansas during 2003 and 2004 to assess potential dispersal capacity of this species. The beetles were reared in the laboratory and one- to two-week-old unsexed beetles were released in the center of a grid of 46 Lindgren funnel traps placed in concentric circles at 50, 100, 200, 400, 600, 800, and 1,000 m from the center towards north, north-east, east, south-east, south, south-west, west, and northwest directions away from the release point. Of a total of 62,400 beetles released over multiple dates, 872 (1.4%) were recaptured. Beetles dispersed a mean (±SEM) distance of 380.4 ±10.5 m, with a range of 50 and 1,000 m (maximum distance in grid). However, Delta sticky traps placed as far away as 3.6 km from the release center recaptured a few (n=3) marked beetles suggesting that R. dominica is capable to fly significantly longer distances than our recapture grid. There was no difference between the sexes in dispersal distance and dissection of recaptured female beetles revealed mature and immature eggs suggesting that this species is iteroparous.

Beetles were also trapped at two- to three-week-intervals in an agricultural landscape in Dickinson Co., Kansas, using a grid of 203 aggregation pheromone baited sticky traps from May to November 2003 and April to November 2004, to assess the spatial-temporal distribution of beetles in relation to farm bins and other geographic features. During spring of both years, beetles were captured near wooded areas, whereas during summer beetles were trapped in both wooded areas and near farm grain storage locations and during fall were trapped predominantly in wooded areas. Three flight activity peaks of trapped beetles were observed in spring, summer, and fall. A degree-day model and female egg development status suggest the existence of two generations of this species in Kansas. The spatial distribution of the captures of beetles in spring and fall suggests that R. dominica overwinters mostly in deciduous forest areas.