Biology of shoot and fruit borer, Earias vittella Fabricius (Noctuidae: Lepidoptera) on okra

The biology of fruit and shoot borer (Earias vittella F.) was studied under the natural conditions in the instructional farm of Uttar Banga Krishi Viswavidyalay in pre-kharif, kharif and post-kharif on okra. The study revealed that the egg incubation in pre-kharif, kharif and post-kharif revealed that the egg incubation were 3.18±0.40, 3.61±0.70 and 4.25±0.67 and larval period were 11.00±0.88, 11.00±0.82 and 13.01±1.81 during corresponding seasons respectively. The pupal period in pre-kharif, kharif and postkharif were 13.01±1.81; 11.00±0.82; 10.97±2.15 days respectively. The adult male longevities observed were 3.64±0.67, 5.60±0.70 and 7.33±0.97 during pre-kharif, kharif and post-kharif. On the other hand female longevities observed were about 7.45±1.57b; 8.87±1.10; 9.41±1.51 days in corresponding seasons respectively. The female fecundity during pre-kharif, kharif and post-kharif were 91.55±10.93, 117.55b±10.60 and 132.04±5.83 eggs in their lifetime. The pre-oviposition during pre-kharif, kharif and post-kharif were 1.64±0.50, 1.52±0.53 and 1.88±0.57 and the oviposition periods in corresponding seasons were 2.73±0.47, 3.22±0.79 and 4.32±0.52. While post-oviposition periods in pre-kharif, kharif and post-kharif were 3.09±0.70, 4.14±0.63 and 3.23±0.92 respectively. Its total life-cycle was completed in 27.45±1.57, 31.60±1.90 and 41.35±2.55 days during pre-kharif, kharif and post-kharif respectively. Higher fecundity may lead to faster population growth that may surpass the economic threshold level (ETL), even though the shoot and fruit borer’s life cycle is longer in Kharif and post-kharif. Thus, it may be said that the kharif and poskharif seasons are the most susceptible to shoot fruit and shoot borer infestation.