Efficacy of selected localized injectable chemical treatments against Cryptotermes brevis (Isoptera: Kalotermitidae) in naturally infested lumber

Abstract:
A number of previous studies have reported superior levels of efficacy for slow-acting, non-repellent toxicants in laboratory simulations against drywood termites, but very little research has been conducted in naturally infested wood. We utilized boards naturally infested with Cryptotermes brevis (Walker), extracted from hardwood shipping pallets. We sought to compare the efficacy of various experimental treatments: untreated (nothing), solvent control (distilled water), 0.05% imidacloprid suspension concentrate (Premise 0.5 SC), 0.05% imidacloprid water soluble packets (Premise 75), 15% disodium octaborate tetrahydrate (DOT, Tim-Bor 98 SP), and 0.05% spinosad SC (Tracer). These treatments were randomly assigned to boards within size class blocks and two duration blocks, 28 and 56 days. Injections were limited to a single point on each board, which had the highest degree of visible drywood termite activity. Upon breakdown, boards were first cut into sections and split apart to extract termites. The numbers of living and dead termites extracted from individual sections were summed over boards and percent dead was calculated; treatment effects were analyzed with an ANOVA model. There was no effect of post-treatment duration, board-size, or the injection quantity on percent dead. Pooled mean (n=12) percent dead ranged from 17.1 % for Premise 0.5 SC to 60.2% for DOT, among the chemical treatments, while the water and non-treatment controls produced 32.4% and 4.5% dead, respectively. There were overall significant treatment effects. While individual mean comparisons indicated that DOT was significantly different from the untreated control, the remaining treatments were intermediate in their effects. None of the toxicants was significantly different from the solvent (water) control. Although the experimental conditions were highly constrained, the results demonstrate that spot-treatment is a hit-or-miss proposition. Interestingly, there was a relatively high degree of mortality (mean = 32% dead) resulting from the injection of water alone; a phenomenon known as “water poisoning” that may indicate that highly desiccation-tolerant species cannot tolerate emersion in liquid water, as has been observed by other authors.