Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2004
Publication Date: September 1, 2004
Citation: Campbell, J.F., Arbogast, R.T. 2004. Stored-product insects in a flour mill: population dynamics and response to fumigation treatments. Entomologia Experimentalis et Applicata. 112:217-225. Interpretive Summary: For food processing facilities, the distribution of pests in and around facilities and the influence of season and pest management practices on pest population dynamics are not well understood, but this information is important for selecting management tools, determining need for treatment, and evaluating efficacy and causes of rebound after treatments. Use of pheromone trapping to assess pest populations is increasing in the food industry and could be a useful tool for making pest management decisions, but because these traps capture primarily insects that are moving between resource patches, it can be difficult to relate pheromone trap capture with actual infestation levels within a facility. The objective of this study was to investigate seasonal trends in stored-product insect trap capture, relationships between trap captures inside and outside the mill and between pheromone trap capture and product infestation, and impact of fumigation on pest populations. Our results indicate that pest species followed one of two general patterns. The first pattern was that source patches for the insects lay over a spatial scale greater than the mill itself, effectively linking activity inside and outside the mill. This reduced the efficacy of treatments such as fumigation and decreased the ability of pheromone trapping to predict level of infestation within the mill. The second pattern suggests source patches for the insects lay over a spatial scale contained within the mill itself with pheromone/food traps capturing primarily insects moving among these internal patches. Pheromone trapping was correlated with infestation and fumigation was more effective. Variation in the rate of pest resurgence after fumigation treatment was determined. The combination of using different monitoring methods and placing traps both inside and outside the facility provided complementary information that helped resolve some of the issues with pheromone trap interpretation. These findings will ultimately help improve our ability to monitor stored-product pest populations using pheromone traps.
Technical Abstract: In a wheat flour mill, seasonal trends in stored-product insect trap capture, relationships between trap captures inside and outside the mill and between pheromone trap capture and product infestation, and impact of fumigation on pest populations were assessed. Mark-recapture was used to evaluate the potential for movement of insects outside the mill into the mill. For Plodia interpunctella (Hübner) (Lepidoptera, Pyralidae) and Trogoderma variabile Ballion Coleoptera, Dermestidae), pheromone trap captures outside were higher than inside the mill, inside and outside trap captures were correlated, both indoor and outdoor trap captures tended to cycle according to a seasonal pattern, fumigations did not consistently influence pheromone trap captures, and in only one instance were they found in product samples. Mark-recapture data indicated that P. interpunctella was capable of entering the building from outside. Tribolium castaneum (Herbst) (Coleoptera, Tenebrionidae) trap captures, in contrast, tended to be lower outside compared to inside, followed a pattern of sharp decline after fumigation treatment and then steadily increased (0.002-0.005 beetles/trap/day) until the next fumigation, this pattern, other then potentially the rate of increase, was not impacted by season and outside trap capture levels, and T. castaneum was the primary species infesting the product. The information generated in this study provides some of the information need to develop improved monitoring and management programs.