Concentration-Dependent Feeding Deterrence to 20-Hydroxyecdysone for Three Subterranean Termite Species (Blattodea: Rhinotermitidae)

Abstract

Effective active ingredients in toxicant bait formulations must be non-deterrent to insect feeding behavior at lethal concentrations. This study evaluated feeding deterrence for Coptotermes formosanus Shiraki, C. gestroi (Wasmann), and Reticulitermes flavipes (Kollar) when provided access to cellulose impregnated with various concentrations of the insect molting hormone, 20-hydroxyecdysone (20E). Termites were exposed to 20E concentrations of 200, 500, 1000 and 2000 ppm and to noviflumuron at 5000 ppm in a 24 h choice-test, and the mass of substrate consumption from treated and untreated media pads was compared for each treatment. 20E feeding deterrence was detected at 500, 1000 and 2000 ppm for C. gestroi, and at 2000 ppm for C. formosanus. No significant differences in consumption of treated and untreated substrate was detected at any concentration for R. flavipes. Potential methods for reducing deterrence are discussed.

Bio-Attractant of termites bait from waste paper and extract Ocimum basilicum Linn against Subterranean Termites Coptotermes curvignathus Holmgren

“…The rate of termite consumption tends to increase with the higher concentration of basil leaf extract. In line with this result, Carnohan et al (2021) stated the concentration of extract was influence the feeding activity of termites. Some extract with higher concentration tend to increase the preference of termite to feed the bait.…”

Feeding cessation after feeding on 20‐hydroxyecdysone in the Formosan subterranean termite

“…One hundred workers and 10 soldiers were placed in each Petri dish. While previous studies provided promising results for 20E such as mortality, target concentration, and faster lethal time than CSIs, [43][44][45] the current study revealed some limitations for the potential use of 20E against subterranean termites. Based on the present study, we argue that 20E cannot be used as a sole AI to eliminate termite colonies.…”

“…8,43,44 To reduce the time taken for colony elimination, 20E, ecdysone, and halofenozide (ecdysone agonists) were tested against the economically important subterranean termites R. flavipes, C. formosanus and C. gestroi. [43][44][45] Results from previous studies suggested that 20E satisfied all requirements to be used as an AI for colony elimination: slow acting, non-repellent, and doseindependent lethal time. Thus far, at the individual level, application of 20E showed promising results, with mortality occurring after about 10 days and intoxicated termites dying from hyperecdysonism.…”

“…44 However, high concentrations of 20E caused feeding deterrence in termites and 1000 ppm was determined to be the threshold concentration to avoid feeding deterrence. 45 These studies indicated a potential for 20E triggering hyperecdysonism in termites as a way to accelerate colony elimination. However, these studies tested 20E on small groups of termites (only workers and soldiers) in Petri dishes in the laboratory, and colony-wide effects of 20E remain to be investigated.…”

“…In another study, the combination of noviflumuron and different concentrations of 20E also demonstrated that over 90% mortality could be achieved within 14 days 44 . However, high concentrations of 20E caused feeding deterrence in termites and 1000 ppm was determined to be the threshold concentration to avoid feeding deterrence 45 …”