Oviposition Behaviour of Sugarcane Adapted Strain of Trichogramma chilonis Ishii (Trichogrammatidae: Hymenoptera)

Abstract

The present study investigates the oviposition behaviour and associated biological attributes of a sugarcane-adapted strain internode borer, Chilo sacchariphagus indicus and top borer Scirpophaga nivella of Trichogramma chilonis under controlled laboratory conditions. Key parameters including fecundity, development period, adult emergence, female emergence and sex ratio were assessed over a five-day oviposition period. Results revealed a significant decline in fecundity from day one (29.7 eggs/female) to day five (7.1 eggs/female), indicating that peak reproductive output occurs immediately post-emergence. The development period remained statistically unchanged across days, ranging from 8.37 to 8.67 days, suggesting that the timing of oviposition does not influence immature development. Adult emergence varied between 83.4% and 89.9%, with the highest emergence recorded on the first day. Female emergence exhibited a gradual decline from 80.5% on day two to 64.1% on day five, with the highest sex ratio (4.2:1) observed on day two. These findings highlight the importance of early oviposition in maximizing reproductive efficiency and female-biased progeny, which are critical for effective biological control. The results demonstrated a progressive decline in fecundity from 28.5 eggs/female on day one to 6.8 eggs/female by day five. The development period remained relatively constant across all days, ranging from 8.37 to 8.67 days, suggesting minimal influence of oviposition timing on immature development. Adult emergence showed a narrow range (85.5–88.2%), with the highest emergence recorded on the first day. A clear decline in female emergence was observed from 81.3% (day one) to 66.6% (day five), indicating reduced reproductive efficiency with female age. The sex ratio remained female-biased throughout the oviposition window, peaking at 4.4:1 on the first day and declining to 2.2:1 by the fifth day.