Potential of Gas-Propelled Aerosol Containing Synergized Pyrethrins for Localized Treatment of Cryptotermes brevis (Kalotermitidae: Blattodea).

Simple Summary: West Indian drywood termite (WIDT) is an invasive insect pest of wood and wood products in Australia, where confirmed infestations have been eliminated using mandatory structural fumigation; however, fumigation is costly, is disruptive, and does not prevent re-infestation. Localized treatments with registered insecticides are the most prevalent and cost-effective ways to treat drywood termite infestations; however, the use of liquid or foam insecticides does not ensure that an infestation has been completely eradicated. The amount of termite frass packed inside a gallery may prevent the chemical from reaching the target spot, and the treatment might not reach all termite galleries, especially during vertical application, which could be a barrier to complete eradication. The current study assessed the potential of aerosol-containing synergized pyrethrins as a spot treatment option for this pest. The results showed that wood surfaces treated with pyrethrins containing aerosol caused a high mortality of WIDT pseudergates in continuous and short exposures. Moreover, in different tests, an aerosol was passed through the loose fecal pellets packed in wooden or silicon tubing, causing high WIDT mortality. The possibility of synergized pyrethrin-containing aerosol as a choice for spot-treating C. brevis in Australia was investigated in laboratory tests. Topical toxicity tests, where C. brevis pseudergates were subjected to multiple doses of pyrethrin mist insecticide, showed the concentration-dependent death of termites with a median lethal dose (LD50) of 193.16 µg. Residual toxicity tests, where the termites were exposed to wood surfaces treated with pyrethrin-containing aerosol, showed a rapid mortality in short and continuous exposures. Less than 20% of the termites survived even when the termites were exposed to a treated wood surface for a minute. All the termites died within 1–5 h in continuous exposure tests, depending on the age of the treated surface. In repellency tests, the termites tended to visit treated surfaces, causing an overall lower survival of the termites. The synergized pyrethrin-containing aerosol remained insufficiently volatile to produce the complete mortality of the termites even after 196 h when there was no contact with a treated surface. The number of termites that survived following the application of the synergized aerosol through a simulated wood gallery or silicon tubing with fecal pellets was also negligible, demonstrating the ability of the aerosol to penetrate through pellets and ultimately resulting in a distribution that is ideal for treatment in the termite galleries. [ABSTRACT FROM AUTHOR]