Biology and management of Harpedona marginata Distant (Hemiptera: Miridae): A pest of Dioscorea species in Sri Lanka

Harpedona marginata Distant (Hemiptera: Miridae) is an emerging pest in Dioscorea cultivations in Sri Lanka. Pest damages were observed in July to September 2017/2018. Thirty three Dioscorea accessions were evaluated at Horticultural Crops Research and Development Institute (HORDI), Gannoruwa and all evaluated accessions were susceptible for this pest. The study was focused on morphological characterization, information on life cycle and chemical control measures of the pest. Male and female insects are morphologically very similar. Head and body have black, 3-4 mm in length. White colour patches were found on infested leaves. In severe infestation, leaves become brownish colour. H. marginata took 26.0 ± 0.47 days to complete its life cycle at 27 0C. Potential insecticides to control H. marginata in laboratory bioassay were 0.75% Neem formulation 5 ml/l (Lakgro neem), Neem seed water extract (30 g/l), Thiamethoxam 25% WG, 0.5 g/l (Actara), Imidacloprid 20% SL, 1 ml/l (Admire) and Thiamethoxam 25% WG + Cloranthraniliprole 20%SC 0.25 g/l (Vertako). Thiamethoxam 25% WG and 0.75% Neem formulations were shown positive results in controlling both adults and nymphal stages of H. marginata in field screening.