COMPARATIVE LIFE TABLE STATISTICS OF Exochomus Nigromaculatus (GOEZE) REARED ON THE PINK MEALYBUG, Maconellicoccus Hirsutus (GREEN), FED ON FOUR HOST PLANTS.

Abstract

Studies on the life and fertility tables of the coccinellid predator, Exochomus nigromaculatus (Gose). were conducted to estimate some of its biological aspects on four different host plants (hibiscus, Sprouted potatoes, Grape and Japanese pumpkins Cucurbita mostchata Duchesne) infested with hibiscus mealybug, Maconellicoccus hirsutus (Green). The stage duration, survival rate, 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 larval stage on Grape, Japanese pumpkins, hibiscus and Sprouted potatoes, were 14.60±0.94, 14.78±1.11, 15.05±0.71 and 17.14±0.94 days, respectively. The total developmental timeof immature stages lasted 29.11±1.1, 29.89±1.13, 30.70±1.03 and 32.27±1.2 days on hibiscus, pumpkin, grape and potatoes, respectively. The stage specific survival of life table data indicated that the mortality factor operated mainly during larval stage. The highest larval survival of 76.63±5.77% was recorded on potatoes followed by 68.9 ± 1.91% on hibiscus and 67.8±1.91 ± 5.1 % on grape; while the least (66.7±10 %) occurred on pumpkin. The fertility of E. nigromaculatus females was relatively high on hibiscus followed by potatoes, pumpkin and grape. The net reproductive rate was 30.37 ± 3.85, 29.18 ± 7.7, 28.94 ± 4.73 and 25.27±6.3 females/ female, respectively, while, the intrinsic rate of increase (rm) was 0.081 ± 0.02, 0.076 ± 0.01, 0.071± 0.01 and 0.068 ± 0.01 females/ female/ day, on pumpkin, hibiscus, grape and potatoes, respectively. The generation time lasted 49.4±6.6, 45.9±4.1, 45.6±4.0, and 43.42 ± 9.9 days, respectively.