Effect of seasonal variation on the biology of lesser grain borer, Rhyzopertha dominica, (Fabricius) on paddy

The life cycle of lesser grain borer, Rhyzopertha dominica, on paddy var Pusa 1121 was studied for seasonal variation at room temperature during winter at 14 to 22±5 oC in winter and at 25±6 oC in rainy season. The result shows that fecundity was more in rainy season (247.6± 13.12 eggs) as compare to winter (123±18.49 eggs). The incubation period was very similar in both seasons i.e. (11.1± 1.52 days) in winter and (11.4±1.50 days) in the rainy season. The total larval and pupal period was 39±3.19 days and the developmental period was 49.8± 4.26 days in rainy season as compare to 81.7±5.89 days and 93.2±9.84 days in winter, respectively. The seasonal variations also have the impact on the longevity of male: female, which was longer (36.5±3.71: 39.3±3.41 days) in winter and shorter (29.1±2.88: 34.9±2.07 days) in rainy season. The sex ratio was 0.80: 1.19 in winter and 0.90: 1.1 in the rainy season. Higher mean growth index 2.91 was recorded in rainy season and lower growth index 1.21 was observed in winter.