MELIACEAE AND RUTACEAE LIMONOIDS AS TERMITE ANTIFEEDANTS EVALUATED USING RETICULITERMES-SPERATUS KOLBE (ISOPTERA, RHINOTERMITIDAE)

Four limonoids were evaluated by a no-choice bioassay method as termite antifeedants using Reticulitermes speratus Kolbe. Obacunone showed the highest degree of antifeeding potency (PC95 = 1133 ppm w/w), followed by nomilin (PC95 = 4475 ppm), azadirachtin (PC95 = 65,293 ppm), and limonin (with PC95 estimates beyond the bioassay limits), which was the least potent. None of the four limonoids exhibited any evidence of acute toxicity towards R. speratus, although termites fed on obacunone and nomilin at concentrations higher than their PC95 estimates tend to die faster than those in the unfed treatment. Obacunone and nomilin also showed a drastic antifeedant consumption (AC) reduction effect at concentrations higher than 510 and 1360 ppm, respectively. With azadirachtin and limonin, such an effect was not observed. The present data suggest that both obacunone and nomilin have an absolute antifeeding activity towards R. speratus.