How varying pest and trap densities affect Tribolium castaneum (Coleoptera: Tenebrionidae) capture in pheromone traps

Authors: Buckman, Karrie; Campbell, James - Jim

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2013
Publication Date: 2/27/2013
Citation: Buckman, K.A., Campbell, J.F. 2013. How varying pest and trap densities affect Tribolium castaneum (Coleoptera: Tenebrionidae) capture in pheromone traps. Entomologia Experimentalis et Applicata. 146(3): 404-412. doi: http://dx.doi.org/10.1111/eea.12039.

Interpretive Summary: The red flour beetle is an important insect pest of facilities which process and store grain. Integrated pest management frequently includes monitoring populations using traps that capture walking individuals. However, fundamental questions remain about the most effective way to implement monitoring programs and interpret monitoring data to estimate beetle density. Using experiments conducted in room-sized chambers where beetle density and number of traps could be controlled, we found that the number of individuals captured in traps increased as density of beetles increased, but the percentage of individuals captured remained constant. Applying a mathematical equation to estimate beetle density based on captures in traps, we found that a trap density of 4 traps per chamber (1 trap per 80 square feet) yielded the most accurate estimate of beetle density. The more traps placed in the chamber the greater the captures of beetles, but when trap density increased beyond 3 traps per chamber (1 trap per 108 square feet) the increases in beetle captures with each additional trap diminished to the point where there was little justification for the increased costs. This is the first scientific information available to guide the number of traps needed to monitor red flour beetles effectively and to estimate beetle density based on captures in traps.

Technical Abstract: The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is an important insect pest in food processing facilities. Pheromone trapping is frequently used to monitor red flour beetle populations in structures; however, the optimal trap density and the relationship between trap captures and beetle density is unknown. Two experiments were performed concurrently in environmentally controlled 30 square meter walk-in chambers to determine the relationship between pheromone trap captures of red flour beetles and beetle and trap number. In one experiment beetle density was kept constant at 200 individuals while trap number was varied from 1-8 per chamber, and in the other experiment trap number remained constant at 1 per chamber while beetle density varied from 20 to 800 individuals. Results indicated that approximately 1 out of 23 red flour beetles were captured in a trap. Number of beetles captured in traps increased significantly as beetle density increased; however, the proportion of beetles captured remained consistent across beetle densities with a mean of 4.7 ± 0.6% of individuals captured. Trap captures varied significantly with trap placement within experimental chambers, indicating that subtle differences in the trapping environment can influence trap captures. Data suggested that trap densities of 0.07 – 0.10 per square meter (2 – 3 traps per chamber) would maximize trap capture, while a trap density of 0.13 per square meter (4 traps per chamber) would maximize the predictive ability of a trapping equation estimating beetle density from trap captures. Results provide preliminary information needed to more thoroughly explore how environmental factors might influence red flour beetle trap capture in the absence of changes in beetle density. Further understanding of these relationships will allow for more accurate assessments of absolute beetle density from pheromone trap capture data.