Factors influencing trap captures of Tribolium castaneum in mills

Tribolium castaneum is an important pest of food processing/storage facilities, and monitoring has been an important method to gather information on population status and response to management strategies. However, it is difficult to draw conclusions on the relationship between number of beetles captured in traps and the actual population density in part because the environment surrounding a trap can affect insect capture. We investigated the distribution of T. castaneum in a five-floor commercial flour mill during a seven year monitoring program, during which frequent fumigations occurred, to evaluate how different components of the environment (both environmental and physical factors) might be correlated with trap captures. Captures in traps before and after fumigation were significantly correlated (P<0.001) at the individual trap level. Among the factors we measured in each trap location, mean temperature was the one most often significantly correlated with trap capture: captures increased with temperature. Other factors such as spillage, distance to wall, and relative humidity also had significant correlations with trap capture. Principal component analysis also supported the hypothesis that temperature in the location where traps were placed was the most significant factor. Although temperature was the factor most often correlated with trap capture, it did not explain a majority of the variation. Therefore, other unmeasured factors may also play a role in determining the variation in trap capture. Our results indicate how trap placement can have an influence on captures, although whether traps are more efficient in capturing in these areas or insect populations are greater in these areas, is not known.