LIFE AND FERTILITY TABLES OF SAN JOSE SCALE, Quadraspidiotus perniciosus COMSTOCK ON DIFFERENT HOST PLANTS

Investigations of life and fertility tables of San Jose Scale (SJS), Quadraspidiotus perniciosus Comstock were conducted to study some of its biological aspects on different host plants (apple, plum and pear). The stage duration, mortality percentage, the net reproductive rate and the intrinsic rate of natural increase were examined. The developmental periods were significantly affected by host plant. The mean duration of the first instar nymph on apple, plum and pear seedlings were 15.8±1.0, 17.5±0.9 and 18.2±0.9 days, respectively. The 2nd instar female lasted by 18.4±1.5, 19.5±1.8 and 21.7±1.2 days; while the 2nd instar male lased 12.2±0.6, 13.4±0.5 and 14.1±0.7 days, respectively. The duration of prepupal and pupal stages reared on apple, plum and pear seedlings lasted 7.5±0.9, 6.3±1.2 and 6.5±0.8 days, respectively. The stage specific mortality of life table data indicated that the death factors operated mainly during first and second instar nymph. The fertility of Q. perniciosus females was relatively high on pear followed by plum and apple. The net reproductive rate was 21.7, 29.5 and 30.9 females/ female on apple, plum and pear, respectively. The intrinsic rate of increase (rm) was 0.043, 0.049 and 0.051 females/ female/ day, respectively. In the same order, the time of generation was 71.7, 69.4 and 67.7 days, respectively.