Temporal variation of phytophagous insects of Calotropis gigantea (L.) in Southern Province of Sri Lanka

Abstract

Calotropis gigantea is a native plant to Sri Lanka having an ayurvedic medicinal value. People use the plant to gain fodder, fiber, and fertilizer. Despite its benefits, the plant is considered as an invasive species in Australia, the USA, etc. As the plant is medicinally, agriculturally, and ecologically valuable, the study was designed to investigate phytophagous insects of C. gigantea and their temporal variation. The field visits were conducted fortnightly from August 2015 to August 2016 in eleven sites in Southern Province (SP). During sampling, the number of insect species, their abundance, and the number of Calotropis fruits were recorded in selected trees. Twenty-nine insect species were recorded from C. gigantea and among them twelve species were phytophagous. Dacus persicus and Paramecops farinosa were destructive phytophagous insects. D. persicus was recorded in all three districts of SP throughout the year and the mean abundance varies significantly (p= 0.002) among districts. P. farinosa was only recorded from Hambantota district. Sphaeroderma sp. was the most abundant phytophagous insect and varied widely across (p = 0.000) districts of Southern Province. Danaus chrysippus larva was observed in all selected sites of SP. None of the insect abundance correlated with Calotropis fruit density, month of year and monthly rainfall.