Seasonal fluctuations of Cotesia flavipes Cameron (Hymenoptera: Braconidae) parasitism in borers of sorghum and sugarcane in southern India

Abstract

Field experiments were carried out at Coimbatore, Tamil Nadu State, India, for four consecutive years (1990-94), to monitor the seasonal activity of Cotesia flcivipes Cameron (Hymenoptera: Braconidae), a larval parasitoid of gramineous borers, including the sugarcane shoot borer (Chilo infuscatellus Snellen), sugarcane internode borer (Chilo sacchariphagus indicus (Kapur) and sorghum stemborer (Chilo partellus Swinhoe) (all Lepidoptera: Crambidae). The highest levels of parasitism (0.0–17.9%) were recorded on Ch. partellus followed by Ch. sacchariphagus indicus (0.0–8.3%) and Ch. infuscatellus (0.0–1.1%). The parasitoid was collected in Ch. partellns and Ch. sacchariphagus indiens in all the four study years, whereas it was not observed in Ch. infuscatellus during 1993-94. Parasitism rates in Ch. partellus were positively correlated with minimum temperature and afternoon RH. In Ch. sacchariphagus indiens, parasitism levels showed significant negative correlation with minimum temperature. Parasitism rates in Ch. sacchariphagus indidus larvae collected during harvest from seven sugar factory areas of Tamil Nadu State were lower in 1992-93 (0.0–1.8%) and higher in 1993-94 (0.0–3.2%) than those recorded at Coimbatore in the corresponding period (December-March). Cotesia flavipes was the only larval parasitoid recorded from the borers both at Coimbatore and the seven sugar factory areas surveyed in Tamil Nadu.