Abstract

Scope and method of study. These studies were conducted to examine relationships between C. ferrugineus population density and quantity of adult insects captured in traps placed in stored wheat. Experiments included a sequence of laboratory studies, a study using electronic insect detection in small steel bins, and a 17-week study conducted in the concrete silos of two country elevators in north central Oklahoma. The laboratory experiments elaborated differences in insect captures under different insect densities, temperatures, probe trap diameters, and number of holes per individual trap. The electronic monitoring study demonstrated how the system could be used in stored wheat and elicited utility in ecological studies of stored-product insects. The field study correlated insect captures in traps with insect density determined with bulk grain samples. Grain temperature, grade, and grading factors were collected throughout the field study to help improve insect population estimates.

Findings and conclusions. Laboratory studies determined that adult C. ferrugineus captures in both WB II probe traps and PC traps were directly dependent on insect density in the grain. Insect captures showed a quadratic response to grain temperature between 20 and 40°C. Probe diameter and number of holes per individual trap did not affect number of insect captures. Finally, dead insects were recovered in probe traps when the insects were found in an aggregated dispersion pattern. The electronic monitoring data showed that electronic counts increased with increasing mean daily air temperature. There was a marked increase in electronic counts in the early evening hours of summer days. Counts did not consistently change in time after probes were positioned in the grain bins. In the field study, grain temperature was important in describing how many adult insects were captured in traps. Multiple regression analysis determined that dockage content, temperature, and probe trap captures together allowed better predictions of actual insect density than probe trap captures alone. Grain samples, obtained from the bottom of the concrete silos immediately after harvest, were heavily infested with key pest species suggesting residual insect infestations.