ORAL TOXICITY AND REPELLENCY OF BORATES TO GERMAN COCKROACHES NDICTYOPTERA, BLATTELLIDAE)

The oral toxicities of boric acid and disodium octaborate tetrahydrate (DSOBTH) in dry-mixed, wet-mixed, and water-based solution baits were determined for German cockroaches, Blattella germanica L., in choice and nonchoice experiments. In dry-mixed, nonchoice bait tests, all coc kroaches died within 1 wk. Time to mortality decreased as the concentr ation of boric acid increased. The LT50s for DSOBTH were not significa ntly different for any concentrations tested. In choice tests, the ord er of LT50s of boric acid and DSOBTH were 6.25% = 12.5% > 25% = 50% an d 25% > 12.5% > 50% > 25%, respectively. Consumption of treated and co ntrol baits and the differences between the LT50s of the nonchoice and choice tests indicate repellency of the toxicants. Most German cockro aches died in 3-6 d in wet-mixed nonchoice tests, but all cockroaches survived the wet-mixed choice tests except at the lowest concentration of boric acid. This result indicated repellency. In nonchoice tests w ith water-based solutions, all cockroaches died in 5 d. In choice test s with boric acid solutions, mortality did not increase at concentrati ons > 1%. Choice/nonchoice ratios indicate no repellency of water-base d solutions. In addition, consumption of treated and blank solutions w as not significantly different for any concentration except 4% DSOBTH.