|STARKUS, LAURA - Arkansas State University|
|MCKAY, TANJA - Arkansas State University|
Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2019
Publication Date: 10/14/2019
Citation: Arthur, F.H., Starkus, L.A., McKay, T. 2019. Degradation and residual efficacy of cyfluthrin as a surface treatment for control of Tribolium castaneum Herbst: effects of temperature and environment. Journal of Stored Products Research. 84:101514. https://doi.org/10.1016/j.jspr.2019.101514.
Interpretive Summary: The pyrethroid insecticide cyfluthrin (Tempo SC Ultra) is used as a residual surface treatment for flooring surfaces in grain storage bins and silos where rough rice is stored, and as a flooring surface treatment in rice milling facilities. However, there are little data regarding how long treatments remain effective after application or how time of year effects insecticide residual persistence. Placing red flour beetle adults on concrete arenas at different times after the concreate was treated with the low and high label rates of Tempo SC Ultra, showed that the time of year (summer vs. autumn) and location (inside an empty grain bin, inside a rice mill, or control location inside a laboratory) impacted the change in insecticide effectiveness over time post-treatment. For both summer and autumn, knockdown (a measure of how quickly the insects are affected by the insecticide) was generally faster on arenas inside the laboratory compared to the grain bin and mill. During the summer knockdown was slower on the arenas held inside the grain bin compared to the mill but was slower in autumn on arenas held inside the mill versus the grain bin. Results show that high and fluctuating temperatures during the summer may have increased degradation rates of the insecticide on the arenas held inside the grain bin. Previous studies using steady temperatures may have overestimated residual persistence under conditions found in grain bins. Facility managers can use this data to more accurately use cyfluthrin as a residual treatment to control stored product insects by taking into account the faster degradation at during the summer months.
Technical Abstract: Concrete arenas were treated with the low and high label rates of cyfluthrin Tempo SC Ultra® (10 and 20 mg Active Ingredient [AI]/m2, respectively) and stored during the summer and autumn in two separate years inside an empty grain bin, inside a rice mill, and inside a laboratory. Bioassays were conducted by removing the arenas at 0 (1 day) to 10 weeks post-treatment from the three locations where they were stored, and exposing adults of Tribolium castaneum (Herbst), the red flour beetle, for 30 minutes to 3 hours on the arenas. Rapidity of knockdown was used to assess residual efficacy. Application rate was significant (P < 0.05) for rapidity of knockdown for the summer storage period but not for autumn (P = 0.05). As the weeks progressed during summer, knockdown was progressively slower during the 30-minute to 3-hour exposure period on arenas held inside the grain bin and the arenas inside the rice mill and the laboratory. During autumn the order was reversed for the grain bin and laboratory as the weeks progressed but at 10 weeks knockdown after 3 hours was still much less on arenas held inside the bin and mill compared to the laboratory. Extreme high temperatures in the grain bin during the summer, and the fluctuating temperatures during autumn, may have promoted residual degradation on arenas held in the bin and mill compared to the constant temperatures in the laboratory. Results show that residual persistence of contact insecticides for control of stored product insects may be less on treated surfaces in field sites, and caution is warranted when predicting time periods for residual efficacy in studies outside of laboratory settings.