A PRELIMINARY STUDY ON THE DURATION OF DIFFERENT LIFE STAGES OF Tetranychus macfarlanei BAKER AND PRITCHARD INFESTING CHRYSANTHEMUM (Chrysanthemum sp.) AT 25°C AND 27°C UNDER LABORATORY CONDITIONS INKOLKATA

摘要

The life cycle of Tetranychus macfarlanei was studied on Chrysanthemum at two temperatures viz 25°C and 27°C in Kolkata, West Bengal and the duration of different life stages were recorded. The incubation period was 1.08±0.30 days at 25°C and thecorresponding figure for 27°C was 1.10±0.30 days. The larval period was 2.02±0.73 days at 25°C and 2.00±0.55 days at 27°C respectively. Protonymphal period lasted for 1.80±0.50 at 25°C and the corresponding figure for 27°C was 1.45±0.30 days. Deutonymphal period was2.40±0.35 days at 25°C and the corresponding figure for 27°C was 2.30±0.80 . Egg to adult period was 5.80±0.80 days at 25°C and the corresponding figure for 27°C was 5.50±0.18 days. Pre -oviposition period lasted for 1.50±0.18 days at 25°C and the corresponding figure for 27°C was 1.40 ±0.16. Oviposition Period was of 10.80±0.20 days at 25°C and in case of 27°C, the corresponding figure wasl4.30±0.10 days. Post — oviposition period was of 1.10±0.20 days in at 25°C and 2.00±0.35 at 27°C . The fecundity of mated female was 150.60±0.20 on chrysanthemum at 25°C and 148.00±0.10 days in case of unmated female. At 27°C, the corresponding figures were 166.80±0.22 days and 160.30±0.15 days respectively. The longevity of female was 18.20±0.75 days and 14.70±0.70 days in case of male at 25°C on chrysanthemum and 22.10±0.85 days and 13.50±0.80 days respectively at 27°C. The sex ratio was studied at 27°C and was found to be 3F: 1M .