Toxicity, repellency, and horizontal transmission of fipronil in the formosan subterranean termite (Isoptera: Rhinotermitidae)

Toxicity of fipronil was evaluated against field-collected Coptotermes forynosanus Shiraki. In topical application assays, fipronil was highly effective against both workers and soldiers at very low doses. Acute toxicity after 24 b was significantly greater in workers than in soldiers. The LD(50)s were 2.59- and 2.91-fold greater with soldiers than with workers from the two tested colonies. The LD(50)s of fipronil at 72 h after treatment were <2.0 ng/insect, with no significant differences regarding the tested workers/soldiers or colonies. Treated soldiers placed with untreated workers significantly increased worker mortality. However, there was no significant horizontal transmission of fipronil from treated workers to untreated soldiers. Fipronil at rates of 0.063% or less showed no repellency, whereas sand treatments of 0.125% fipronil were repellent to termite workers.