Life history, phenology, host range and natural enemies of Acria meyricki Shashank and Ramamurthy (Lepidoptera: Depressariidae): an emerging defoliator of oil palm, Elaeis guineenis Jacq. In India

Oil palm leaf webworm, Acria meyricki Shashank and Ramamurthy (Lepidoptera: Depressariidae) is emerging as serious defoliator of oil palm, Elaeis guineensis Jacq. in India. It damages oil palm of all ages, from nursery to adult palms. A study was conducted in the laboratory to understand the biology and morphometrics of A. meyricki . Abundance and population dynamics of leaf webworm and its parasitoids were studied in oil plantations in Andhra Pradesh, India. Pest density (number of larvae / leaf) and parasitism rates of parasitoids were quantified. Influences of weather factors viz. , maximum and minimum temperature, morning and evening relative humidity and rainfall on the abundance of leaf webworm and its parasitoids were assessed. A female moth laid about 101.60 eggs in its life time. The caterpillars developed through six to seven instars. Total life cycle completed in 32.9 days (egg to adult). Leaf webworm preferred to defoliate the older and intermediate leaves of the palms. Early stage caterpillars of feed on green parenchymatous tissues of the leaflets from under surface leaving a thin parchment like upper epidermis undamaged, while, the later stages defoliate the leaves. In severe cases, leaflets appear widely eroded, thus curling, bending and drying consequently to the pest infestation. The activity of the pest in oil palm plantations was limited to cooler months of the year i.e. October to March. Pearson Co-efficient of correlation analysis showed that minimum and maximum temperatures had significant negative effect on the development of pest population (larval density). Three parasitoids viz. , Dolichogenidea (= Apanteles ) hyposidrae (Wilkinson) , Elasmus brevicornis Gahan and Brachymeria albotibialis (Ashmead) were identified during the study and their role in the pest population changes is discussed. Correlation analysis indicated that the parasitoids, D. hyposidrae and B. albotibialis were significantly and positively correlated with abundance of host larvae and pupae respectively. Results of feeding tests indicated that oil palm was the best host known of all species tested, with higher rate of larval pupation and adult emergence and the lower duration of time to pupation and adult emergence, which was followed by cocoa. The practical implications of this knowledge are discussed.