THE EFFECT OF SEASONAL VARIATION ON REPRODUCTION AND SURVIVAL OF EPHESTIA CAUTELLA WALKER (LEPIDOPTERA: PYRALIDAE) IN COCOA BEANS

J O AKINNEYE

Abstract



The effect of seasonal variation on the development of Ephestia cautella Walker (Lepidoptera: Pyralidae) was investigated in the laboratory at ambient temperature of 28±2oC and 75±5% relative humidity during wet set season and ambient temperature of 34±20C and 65±5% relative humidity during dry season. Fecundity, egg viability, number of generations and longevity of E. cautella were determined in both the dry and wet season of the year. Wet seasons describe April-September 2006 and April to September 2008 while Dry seasons describe October 2005-March 2006 and October 2007-March 2008. The E. cautella females laid more eggs in the wet seasons than in the dry seasons as they recorded 137.30 and 170.16 eggs in the two wet seasons respectively while they recorded 73.41 and 100.50 eggs in the two dry seasons respectively. The wet seasons recorded the longest egg-laying duration of 1 – 9 days and 1 – 15 days respectively while the egg-laying duration for the two dry seasons was 1 – 6 days. The wet seasons recorded the highest egg viability of 85 and 81% respectively while the dry seasons recorded the lowest egg viability. The highest developmental period of 45.60 and 45.50days was recorded for the two wet seasons respectively. The number of generation obtained in wet and dry seasons was 4 and 5 respectively. Isolated virgin adult male and female lived longer in wet season (25.0 and 12.0 days) than those isolated during dry seasons (12.0 and 6.0 days). Male in group of 20males in one vial lived an average of 7 days in dry season and an average of 15 days in wet season. Unmated male and female live longer than their mated counterpart. Moreover, it was noted that all the live stages of E. cautella was effervescent during wet season while dry season could enfeeble them. Hence the development of the insect was altered by seasons.

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