Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2010
Publication Date: June 1, 2010
Citation: Campbell, J.F., Toews, M.D., Arthur, F.H., Arbogast, R.T. 2010. Long Term Monitoring of Tribolium castaneum Populations in Two Flour Mills: Rebound After Fumigation. Journal of Economic Entomology. 103: 1002-1011. DOI: 10.1603/EC09348. Interpretive Summary: Methyl bromide fumigations of food processing plants to manage stored-product insect populations have been a major component of pest management programs. Limited information is available on effectiveness of these treatments and this has hampered the phase out of this fumigant under the Montreal Protocol and adoption of alternative treatments. Here, rebound in red flour beetle (Tribolium castaneum) pheromone trap captures after fumigation was evaluated for 21 fumigations in two wheat mills. Evaluation of the time it took for beetle captures to increase to different thresholds indicated that both time of year fumigation was performed and integrated pest management practices performed within the mill after fumigation both significantly impacted rebound time. Changes in trap captures from one monitoring period to the next were greater above the threshold of 2.5 beetles per trap per 2 week period, suggesting that this threshold might be useful as a management target to reduce risk. These findings provide baseline information on methyl bromide efficacy, but also illustrate how population growth can be manipulated to reduce the need to fumigate.
Technical Abstract: Structural fumigations of food processing plants to manage stored-product insects has been a major component of pest management programs, but limited information on field efficacy is available. Efficacy, based on pheromone trapping data, consists of initial reduction in captures after treatment and rebound in trap captures over time. Pattern of Tribolium castaneum rebound was evaluated after 21 fumigations in two flour mills. Rebound in mean number of beetles captured and the probability of a trap capturing one or more beetles was evaluated. Rebound to a threshold mean beetle capture of 2.5 beetles/trap/two week period took 174 days and rebound took longer after fall (248 days) than spring (104 days) fumigations. Rebound to the probability of capture threshold of 0.50 was 120 days, but there was no significant effect of season. Improvement in IPM practices in one of the mills was associated with an increase in time to reach mean beetle capture threshold (49 days before and 246 days after) but not in time to reach the probability of capture threshold (38 days before and 165 days after). There was a negative correlation between number captured after fumigation and time to rebound to threshold, and after improved IPM there was a significant reduction in the number of beetles per trap immediately after fumigation. Above these two thresholds the degree of change in trap captures is significantly greater than below, which suggests they might be useful in evaluating risk in a pest management program.