Tribolium castaneum (Coleoptera: Tenebrionidae) associated with rice mills: Fumigation efficacy and population rebound

Authors: Buckman, Karrie; Campbell, James - Jim; SUBRAMANYAM, BHADRIRAJU - Kansas State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2012
Publication Date: 2/11/2013
Citation: Buckman, K.A., Campbell, J.F., Subramanyam, B. 2013. Tribolium castaneum (Coleoptera: Tenebrionidae) associated with rice mills: Fumigation efficacy and population rebound. Journal of Economic Entomology. 106(1): 499-512. http://dx.doi.org/10.1603/EC12276.

Interpretive Summary: The red flour beetle is the most important insect pest infesting rice milling facilities in the U.S. While this pest has traditionally been managed by fumigation with methyl bromide, this fumigant is currently being phased out under the 1987 Montreal Protocol. The purpose of this study was to evaluate the effectiveness of sulfuryl fluoride (SF), an alternative to methyl bromide, in managing red flour beetle infestations in rice mills. Red flour beetle populations in and around seven rice mills were monitored before and after 25 fumigations with SF. Beetle populations were estimated by the number of adults captured in pheromone traps. The SF fumigations led to an average of 66% reduction in captures of red flour beetle adults. Beetle captures at the rice mills were strongly influenced by seasonal changes in temperature, with more beetles being captured during the warmer months and fewer during the cooler months. In addition, red flour beetle captures in traps located inside mills were positively correlated with captures in traps located outside of the mill. Seasonal temperature fluctuations also strongly impacted the length of time required for captures to return to pre-fumigation levels. Similar studies in wheat flour mills did not share the seasonal patterns or correlation between captures inside and outside the mills. These results highlight the importance of treatment timing in maximizing fumigation efficacy in rice mills and suggest there is a fundamental difference in red flour beetle population dynamics and in the impact of fumigation between wheat and rice mills.

Technical Abstract: The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is the most important stored-product insect pest infesting rice mills in the U.S. Due to the phasing out of methyl bromide in accordance with the 1987 Montreal Protocol, the efficacy of alternative fumigants in controlling flour beetles in mill structures must be evaluated. Long-term trapping data sets (2 – 6 years) of T. castaneum in and around seven rice mills were analyzed to assess the efficacy of sulfuryl fluoride fumigation (n = 25). Fumigation efficacy was evaluated as the percentage reduction in mean trap captures of adults and proportion of traps capturing at least one adult beetle. Beetle trap captures fluctuated seasonally, with increased captures during the warmer months of June through September that dropped off during the cooler months of October through March. Fumigations resulted in a 66 ± 6% (mean ± SE) reduction in mean trap captures within mills and a 52 ± 6% reduction in the proportion of traps capturing at least one adult beetle. Lengths of time for captures to reach pre-fumigation levels, or rebound rates, were variable and adult capture levels inside were most influenced by seasonal temperature changes. Temperatures inside mills followed those outside the mill closely, and a significant positive relationship between outside temperatures and trap captures was observed. Inside and outside trap captures exhibited a significant, positive relationship, but fumigations consistently led to reductions in beetle captures outside of mills, highlighting the interconnectedness of populations located inside and outside mill structures.