Field evaluation of fipronil and chlorfenapyr against the desert subterranean termite (Heterotermes aureus)

Non-repellent insecticides are a fundamental tool for the control of subterranean termites. One of their advantages is the possibility of transference among nestmates which results in mortality at a distance from the site of application. We tested two non-repellent termiticides, Fipronil and Chlorfenapyr, for their effect on termite foraging activity of colonies of the desert subterranean termite (Heterotermes aureus). Testing was done in the Santa Rita Experimental Range in southern Arizona. We established nine experimental grids (three for each insecticide treatment and the untreated control) consisting of 51 termite monitoring stations each. Termites were collected monthly and counted. For the fipronil experiment, we monitored termite activity for nine months before and 18 months after treatment. For the chlorfenapyr experiment, termite activity was recorded for 12 months before and after application. Multiple regression analyses were performed to detect activity changes in the treated grids that had no corresponding changes in the controls. In the fipronil treated grids, a significant reduction in termite activity was observed in the stations close to the treated area and a few of the other stations on the grid. The effect on the entire grids was not significant. In contrast, chlorfenapyr produced a reduction in termite activity that encompassed entire grids. Our results indicate that both insecticides tested have an effect beyond the immediate site of application. The area covered by this effect is greater for chlorfenapyr.