Abstract

A study was undertaken over two cropping seasons, 2018/2019 and 2019/2020, to determine the economic injury level for carmine spider mite, Tetranychus cinnabarinus (Boisduval) on tomato Solanum lycopersicum in Botswana. Tomato plants were infested with adult spider mites for durations of 0 (no exposure), 1, 2, 3, 4, 5, 6 and 7 weeks (complete exposure). The corresponding treatments were 7, 6, 5, 4, 3, 2, 1 and 0 sprays with Abamectin. The results showed a significant reduction in the number of spider mites per plant as the frequency of spraying increased. An inverse relationship between spider mite exposure and yield was also observed following three weeks exposure. Yield loss increased to more than 50% when the pesticide was not applied to control spider mites. Economic decision levels are fundamental components of cost effective IPM programs and can be effective tools for making decisions about the application of pesticides against carmine spider mite in Botswana.

Key words: Spider mite exposure, Tetranychus cinnabarinus, economic injury level, yield loss, Solanum lycopersicum.