Influence of Apple Cultivars on the Development and Fecundity of the Two-Spotted Spider Mite, Tetranychus urticae (Koch)

Abstract

Development and reproduction of two-spotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae) were studied under laboratory conditions (Temp.25±1°C; RH 70-80%; LD 16:8) to determine the influence of three apple cultivars (Fuji, Tsugaru and Hongro). The results indicated that the development of the mite increased more rapidly on Fuji than rest of the studied cultivars. Developmental periods of the mite were 7.06±0.14, 7.14±0.09 and 7.58±0.17 days in the cultivars of Fuji, Tsugaru and Hongro, respectively. Mortality (%) was 26.00±0.36, 30.11±0.73 and 40.11±0.53 and sex ratio were 75.88±0.60, 74.05±0.46 and 80:07±0.61 on Fuji, Tsugaru and Hongro, in that sequence. Oviposition periods were 17.28±0.28, 22.06±0.36 and 27.72±0.62 days with the adult longevity of 20.89±0.30, 26.22±0.31 and 31.44±1.00 days on Fuji, Tsugaru and Hongro cultivars, respectively. Those completed their lifecycle around the average of 27.94±0.37, 33.36±0.37 and 39.03±0.97 days, on Fuji, Tsugaru and Hongro cultivars, correspondingly. T. urticae performed better fecundity on Tsugaru than on the other cultivars, due mainly to high egg production (75.20±1.16 eggs/ female) followed by Fuji (71.17±1.17 eggs female^-1) and Hongro (45.44±1.62 eggs/ female). Mean generation time (T) of the population ranged from 16.73 days on Fuji while 20.18 days on Hongro. The net reproduction rate Ro was high on Fuji (47.36) and low on Hongro (32.72). The highest rm occurred on Fuji (0.23 ♀/♀/day) and the lowest on Hongro (0.18♀/♀/day).