CONSEQUENCE OF HOST PLANTS AND SEASONS ON THE BIOLOGY OF THE TWO-SPOTTED SPIDER MITE TETRANYCHUS URTICAE (KOCH)

Abstract

The two-spotted spider mite, Tetranychus urticae Koch (Tetranychidae), is highly polyphagous and serious pest of vegetables, fruits and other crops in Bangladesh. There are many factors are responsible for buildup the population of Tetranychus urticae. Among them seasons and the diverse host plants may have the effects on this pest; therefore the developmental and reproductive biology of the two-spotted spider mite, Tetranychus urticae were studied in summer provided leaves of bean and cow-pea, as well in winter while fed brinjal, cow-pea, cabbage and bean. All the parameters were studied under prevailing laboratory conditions. Immature developmental time and adult longevity were inversely related to seasons. The results indicated that the development of the two-spotted spider mite increased more rapidly on bean in summer than rest of the tested hosts. The longest developmental period was 41.94 and 41.07 days for female and male, respectively in winter when the T. urticae was fed on cow-pea. On the contrary, it was shortest 11.25 and 10.39 days for female and male in summer while reared on bean. Lifetime fecundity was highest (62.71 + 1.45) on bean in summer and it was lowest (36.4 + 0.42) on bean in winter. The sex ratio (proportion of male) was highest (0.35) in winter and lowest (0.24) in summer on cowpea. Survivorship during immature development varied from 82.14 to 95.65%, with the lowest rate on bean in summer. Life table parameters were also analyzed and the generation time (7) was lowest (20.37) in summer when fed on bean, the net reproductive rate Ry was highest (36.29) in summer when fed cowpea and both r,, (0.17) and A (1.19) were highest in summer when fed on bean.