Evaluation of Some Essential Oils as Repellents to the Indian HoneybeeApis Cerana Indica1. Gustatory Repellency and Toxicity

SummaryEssential oils were obtained by water distillation of seeds of ajwan (Trachyspermum ammi (L.)) and leaves of chenopodium (Chenopodium ambrosioides L.), citronella (Cymbopogon nardus (L.)), eucalyptus (Eucalyptus spp.) and lantana (Lantana camara L.). Oils were evaluated in the laboratory for gustatory repellency (CCR50) and stomach toxicity (LD50) to worker honeybees of A. c. indica using benzaldehyde as a reference standard. Oils of ajwan, citronella, chenopodium, lantana and eucalyptus respectively were 6·49, 5·95, 3·20, 1·31 and 0·69 times as repellent and 3·74, 1·15, 2·15, 1·10 and 1·36 times as toxic to bees as benzaldehyde. The order of safety to bees (ratio of LC50 to CCR50) was citronella (11·36) > ajwan (3·81) > chenopodium (3·27) > lantana (2·62) > benzaldehyde (2·19) > eucalyptus (1.11). On the basis of its high gustatory repellency, low toxicity and high margin of safety, citronella appears to be a promising candidate for further repellency tests.