Trap catches of stored-product insects before and after heat treatment in a pilot feed mill

The pilot feed mill at Kansas State University was heated to temperatures of 50°C for 28–35 h during August 4–6, 1999 using natural gas heaters to kill stored-product insects. A three-parameter nonlinear regression model satisfactorily described temperature profiles on each of the four mill floors and was useful in showing differences among floors in the number of hours taken to reach 50°C and hours above 50°C. Pitfall traps with food and pheromone lures and sticky traps with pheromone lures were used to sample adults of beetles and moths, respectively, between July 8 and December 1, 1999 to evaluate heat treatment effectiveness. A total of 32 insect species representing 26 families in seven orders were captured in traps. Immediately after heat treatment, there was 95% reduction in total beetle captures in pitfall traps and 99% reduction in moth captures in sticky traps. Trap captures of the almond moth, Cadra cautella (Walker) and cigarette beetle, Lasioderma serricorne (L.) were significantly reduced and remained low after heat treatment. However, trap captures of the flat grain beetle, Cryptolestes pusillus (Schöenherr), Indianmeal moth, Plodia interpunctella (Hübner), and red flour beetle, Tribolium castaneum (Herbst) increased gradually after heat treatment, especially on the 1st and 4th floors. Our results indicated that traps are valuable tools for gauging the degree and duration of insect suppression obtained by heat treatment. In addition to trapping, visual inspection of the mill areas and absolute sampling of ingredients, products and spillage should be undertaken, so that areas of incipient insect reinfestation can be identified and potential problems rectified or averted.