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)

Three factors, viz temperature [T], host density [N] and plant cultiva r [C] resistant cultivar Ganga-5 [RC] and susceptible cultivar Type-41 [SC] were studied that could affect the intrinsic rate of natural inc rease [r(m)] and offspring sex ratio [sr] of the parasitoid [P] Lysiph lebia mirzai Shuja-Uddin 1975. Following relationships between r(m,) N and sr were observed: r(m)(RC)=0.2628 - 0.1240 sr + 0.0174 ln N; r(m) (SC) = 0.2807 - 0.0939 sr + 0.0080 ln N. These relations show that wit h the increase of N or decrease in sr, r(m) increases. The pooled sr i n the present study was 0.2682 and 0.4842 on RC and SC, respectively a t 100 N and the observed values of r(m) were 0.330 and 0.282, respecti vely on RC and SC. The variation between the observed and estimated va lues 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 equat ions. Similarly there exists interrelationship between sr and T (degre es C). The regression equations between r(m,) N and T (12-22 degrees C ) at both food plant C are as follows: r(m) (RC) = 0.0840 In T + 0.017 4 ln N - 0.0212; r(m) (SC) = 0.0287 ln T + 0.0080 ln N + 0.1448. By th e help of these equations one can predict the growth rate of the popul ation of L. mirzai at given T, N and sr. Higher values of constants li nked with T and N on RC implies the better performance of the P at hig her 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 agri cultural pests, and the variable breeding is traditionally in the bota nical field of plant breeding and falls rather outside the scope of bi ological control workers. Information about its compatibility with bio logical control necessitate interdisciplinary action in achieving good pest management.