Immigration of insects into bins storing newly harvested wheat on 12 Kansas farms

Adult insects entering 34 bins (36–238 t capacity) storing newly harvested hard red winter wheat on 12 farms in Kansas were sampled from July through December 1998 using ventilation traps. Insects moving through the grain stored in these bins were sampled using probe traps. During the fourth week of storage, probe traps captured Cryptolestes ferrugineus in all bins, Ahasverus advena in 32 bins, Typhaea stercorea in 31 bins, and Rhyzopertha dominica in 13 bins. Means±SE of 5.6±0.7 C. ferrugineus, 0.5±0.2 R. dominica, 3.5±0.3 A. advena, and 3.5±0.7 T. stercorea were caught per day in probe traps. Ventilation traps provided a more direct measure than probe traps of the total numbers of insects entering bins storing newly harvested wheat. Immigration of A. advena and T. stercorea increased more than that of other species during the storage period, exceeding that of C. ferrugineus and R. dominica during some weeks. Rhyzopertha dominica had the lowest immigration rate. Bin size did not influence ventilation trap catch but as many as a third more insects may immigrate into large bins at the eaves compared with small bins because of their larger circumference. The mean numbers of C. ferrugineus, R. dominica, A. advena and T. stercorea captured in ventilation traps at the bin cap were 7.8, 2.7, 15.1 and 18.3 times, respectively, those captured in ventilation traps at the bin eaves. The estimated means±SE for total numbers of insects entering a bin each day were 13.6±4.2 C. ferrugineus, 6.3±4.7 R. dominica, 5.8±1.4 A. advena, and 21.9±8.2 T. stercorea. Estimates of immigration rates can improve the accuracy with which insect densities are predicted using insect population growth models, and allow computer models to be used more effectively in managing insect pests. Insect infestations may be reduced by screening the openings between the bin cap and the roof, or the roof and the side walls.