Residual Effects of Termiticides on Mortality of Formosan Subterranean Termites, Coptotermes Formosanus Shiraki, in Substrates Subjected to Flooding
Semester of Graduation
Master of Science (MS)
Department of Entomology
Formosan subterranean termites (Coptotermes formosanus Shiraki) are one of the most important economic insects in the Southern US since they cause severe and costly damage to properties. Soil treatment with termiticides is the most widely used and reliable method for termite prevention, but their efficacy after a home floods, an all too common event for a homeowner in recent years, has prompted many pest control companies to suggest a new treatment is necessary. This can be expensive and possibly unnecessary. However, several factors such as termiticide water solubility and binding properties, soil type and soil leachability and the inherent toxicity of different termiticides, even at low concentrations, must be considered. We set out to address this little studied issue in a controlled laboratory setting. Colonies of C. formosanus were collected from Brechtel Memorial Park in New Orleans using a termite milk crate trap method. The termiticides chosen for study are among the most commonly used today and included: fipronil, imidacloprid, chlorantraniliprole and bifenthrin. Evaluation of 1, 10 and 25 ppm of each termiticides in sand and soil (Wt/Wt basis; 3 replications for each combination using two colony groups) was done. Comparison of the mortality of C. formosanus in no- choice bioassays exposed to flooded (for 1 week) and unflooded substrates were done. The results indicate that for bifenthrin and fipronil mortality of C. formosanus was not affected by flooding regardless of soil type except at the lowest concentration tested. Chlorantraniliprole toxicity was lower after a flood at 1 ppm in sand but otherwise similar at higher concentrations. In soil, mortality was generally low but unexpectedly higher at 10 ppm and 25 ppm in flooded compared to unflooded soil. For all concentrations of imidacloprid treated sand, mortality of C. formosanus was reduced after a flood. However, at high concentrations in soil, flooded conditions increased its toxic effects on C. formosanus.
Sapkota, Rajani, "Residual Effects of Termiticides on Mortality of Formosan Subterranean Termites, Coptotermes Formosanus Shiraki, in Substrates Subjected to Flooding" (2018). LSU Master's Theses. 4761.