Biology of the Cassava Mite, Tetranychus truncatus Ehara (Acari: Tetranychidae)

Abstract

The duration of developmental stages of Tetranychus truncatus Ehara was studied at four different temperature regimes (20, 25, 30 and 35˚C) on excised mulberry leaves. Longevity and fecundity of fe-male and sex ratio were also observed at 30˚C. Mites completed their development within this tem-perature range. T. truncatus eggs hatched to larvae in the shortest duration of 2.38 ± 0.06 days at 35˚C and the longest duration of 7.65 ± 0.05 days at 20˚C. Development time for completion of the life cycle de-creased significantly with increasing temperature. The longest (16.93 ± 0.11 days) and the shortest (5.34 ± 0.11 days) life cycle were observed at 20˚C and 35˚C respectively. The highest immature mortality was 13.94% at 35˚C followed by 10.35% at 20˚C. A female mite laid 55.07 eggs during its oviposition period of 10.93± 0.29 days at 30˚C. The oviposition rate was 5.13± 0.24 eggs/female/day at 30˚C. The sex ratio of T. truncatus at 30˚C was 1 : 3.12 (male: female)