Diurnal population trends of Megalurothrips sjostedti and Frankliniella occidentalis (Thysanoptera: Thripidae) and their natural enemies on French bean Phaseolus vulgaris (Fabaceae)

Abstract

A field experiment was conducted to track the daily population trends and occurrence of the flower thrips Megalurothrips sjostedti Trybom and Frankliniella occidenialis (Pergande), and their indigenous natural enemies Orius spp. and Ceranisus menes (Walker), infesting French beans. French beans in monocrop or interplanted with six companion crops (Zea mays L., Coriandrum sativum L., Tagetes erecta L., Brassica oleracea var. acephala L., Daucus carota L. and Capsicum annuum L.), and two chemical insecticides, methiocarb (Mesurol 500SC) and t.-cyhalothrin (Karate 1.75% EC), were evaluated for their effects on the abundance of flower thrips, throughout the day, at l-h intervals. The average population peak of thrips was found to occur at around 1300h, but each species had different peak periods. Adult F. occidentalis populations peaked at midday and adult M. sjostedti populations at 1500 h, while the larvae of the two thrips species peaked at around 1300 h. Orius spp. were the most abundant natural enemies and their populations peaked at around 1400 h. Ceranisus menes population also peaked at around 1400 h.