Rice skipper, Pelopidas thrax (hubner) (Hesperiidae: lepidoptera): An emerging insect pest in rice fields in Egypt, host plants, population fluctuation, damage and related natural enemies

Abstract

Rice (Oryza sativa L.) is a very important food crop in Egypt, particularly with shortage of wheat production for consumers. Insect pests are one of challenges against high yield productivity. Experiments and observations conducted at rice fields at Sakha Agricultural Research Station, Egypt during 2019, 2020 and 2021 seasons revealed occurrence of an emerging insect pest; rice skipper, Pelopidas thrax (Hubner) (Hesperiidae : Lepidoptera) . Larvae of skipper fed upon leaves of rice, barnyardgrass and juncle rice. Adult activity was low in June - July, increased by mid-August, and maximum by late August, and throughout September, with 3-4 seasonal peaks. In general, the damage in rice plants was low, so, the simulation technique, based upon removing certain areas of the flag leaves, was adapted. The treatments (removed areas); 0, 25, 50, 75 and 100 %. Induced reductions of 4.47-23.05% filled grain percentage, 2.07-6.61% in 1000-grain weight, and 5.95-31.86% in grain yield respectively. Seven parasitoid species were recorded. They are Trichogramma evanescens (on skipper eggs), Telenomus sp. (eggs), Chelonus sp. (egg-larva), Anomalon sp. (larvae), Cotesia ruficrus (lavae), Brachymeria sp. (pupae), and Exorista sp. (larvae). Also, two insect predators were found associated with P. thrax; Anatrichus pygmaeus, Paederus alfierii as well as the spider, Argiope trifasciata. Till now, Pelopidas thrax (Hubner) is considered a minor pest. Because of expected climatic changes and disturbances in rice ecosystem due to excessive use of pesticides, this skipper may become a major insect pest. Further studies are required to reveal additional biological and ecological aspects of this emerging insect.