Interrelationship Between Host Density, Temperature, Offspring, Sex Ratio and Intrinsic Rate of Natural Increase of the Aphid Parasitoid Lysiphlebia mirzai Reared on Resistant and Susceptible Food Plant Cultivars (Hymenoptera: Braconidae: Aphidiinae)
Biswas, Shilu; Singh, Rajendra
Three factors, viz temperature [T], host density [N] and plant cultivar [C] resistant cultivar Ganga-5 [RC] and susceptible cultivar Type-41 [SC] were studied that could affect the intrinsic rate of natural increase [rm] and offspring sex ratio [sr] of the parasitoid [P] Lysiphlebia mirzai Shuja-Uddin 1975. Following relationships between rm, N and sr were observed: rm (RC) = 0.2628 - 0.1240 sr + 0.0174 ln N; rm(SC) = 0.2807 - 0.0939 sr + 0.0080 ln N. These relations show that with the increase of N or decrease in sr, rm increases. The pooled sr in the present study was 0.2682 and 0.4842 on RC and SC, respectively at 100 N and the observed values of rm were 0.330 and 0.282, respectively on RC and SC. The variation between the observed and estimated values by the above equations are very small: 3.4% on RC and 4.1% on SC which strengthen the confidence in the predictive power of these equations. Similarly there exists interrelationship between sr and T (°C). The regression equations between rm, N and T (12-22 °C) at both food plant C are as follows: rm (RC) = 0.0840 ln T + 0.0174 ln N - 0.0212; rm (SC) = 0.0287 ln T + 0.0080 ln N + 0.1448. By the help of these equations one can predict the growth rate of the population of L. mirzai at given T, N and sr. Higher values of constants linked with T and N on RC implies the better performance of the P at higher T and N at RC than SC. Though the development of RC offers a sound and very practical approach to the long range control of certain agricultural pests, and the variable breeding is traditionally in the botanical field of plant breeding and falls rather outside the scope of biological control workers. Information about its compatibility with biological control necessitate interdisciplinary action in achieving good pest management.