Effectiveness of three pesticides against carmine spider mite (Tetranychus cinnabarinus Boisduval) eggs on tomato in Botswana

The carmine spider mite (CSM; Tetranychus cinnabarinus Bois.) is one of the most destructive pests of vegetables, especially tomatoes. Its management in Botswana has, for years, relied on the use of pesticides. This study evaluated the efficacy of abamectin, methomyl and chlorfenapyr against CSM eggs under laboratory conditions in Botswana. Each treatment was replicated three times. The toxic effect was evaluated in the laboratory bioassay after 24, 48 and 72 h of application of pesticides. This study revealed that chlorfenapyr was relatively more effective since it had lower LD50 values than those for abamectin and methomyl. It was further revealed that at recommended rates, 90% mortalities occurred 48 h after application of methomyl and chlorfenapyr, while abamectin did not achieve 90% mortality throughout the study period. This implies that abamectin requires extra dosages to achieve mortalities comparable to those of the other two pesticides. The study has found that chlorfenapyr was the most effective insecticide followed by methomyl and then abamectin when applied on CSM eggs. Further research and field testing is necessary to confirm these laboratory findings. Key words: Abamectin, methomyl, chlorfenapyr, effectiveness, carmine spider mite, tomato.