Biology of the Brinjal Shoot and Fruit Borer, Leucinodes orbonalis Guenée (Lepidoptera: Crambidae), under Laboratory Conditions

Abstract

The brinjal shoot and fruit borer, Leucinodes orbonalis Guenée (Lepidoptera: Crambidae), is a destructive insect pest of brinjal that causes substantial yield losses by damaging shoots and fruits throughout the crop growth period. A laboratory investigation was conducted during the summer of 2024 to study the biology and morphometrics of L. orbonalis on brinjal. Infested fruits collected from the field were used to establish a laboratory culture, and observations were recorded for the egg, larval, pupal, and adult stages under ambient laboratory conditions. The eggs were creamy white and were laid singly or in clusters, with mean lengths and widths of 0.72 ± 0.07 mm and 0.43 ± 0.05 mm, respectively. The incubation period ranged from 3–5 days, with a mean of 3.4 ± 0.7 days, and the mean hatching percentage was 64 ± 9.06%. The larvae completed five instars, with a total larval duration of 13.3 ± 1.45 days, whereas the mean pupal period was 8.25 ± 1.45 days. The mean pre-oviposition, oviposition, and post-oviposition periods were 1.0, 3.10 ± 0.64, and 1.20 ± 0.41 days, respectively. Female moths survived longer (5.05 ± 1.19 days) than males (3.05 ± 0.76 days) and laid a mean of 147.6 ± 28.67 eggs per female. The female-to-male sex ratio was 1.7:1. Morphometric observations indicated progressive increases in body size across successive larval instars, with the fifth instar measuring 17.22 ± 1.20 mm in length and 3.95 ± 0.57 mm in breadth. The pupa measured 11.76 ± 1.26 mm in length and 4.04 ± 0.42 mm in breadth, whereas adult females were larger than males in body dimensions and wing expanse. These findings provide condition-specific baseline information on the developmental biology and morphometric characteristics of L. orbonalis for subsequent validation in pest-development forecasting and integrated pest-management research.