Pakistan Research RepositoryTRI-TROPHIC LEVEL INTERACTION AMONG HOST PLANT (RAPESEED-MUSTARD), TURNIP APHIC (LIPAPHIS ERYSIMI KALT.), PARASITOID (DIAERETIELLA RAPARE M’INTOSH.) AND ITS AUGMENTATION ON BRASSICA NAPUSS. AhqabullahKakakhelauthorStudies were conducted on tri-trophic level interaction among host plant, turnip aphid, parasitoid and its augmentation on B.napus. impact of various moisture levels. Row spacing by intercropping B. Napus with wheat and effect of aphid’s population densities of L. erysimi on its growth and development when reared on susceptible and moderately resistant cultivars of rapeseed-mustard under field and laboratory conditions. The increase of aphid’s population density favoured the augmentation of D. rapae during pod stage of the crop development L. erysimi was smaller in size at flowering stage compared to pod and leaf stages under the field conditions. The female parasitoids attained the pattern of pod> leaf> flowering stages, whereas, males had an opposite pattern to that of females for increase in their body size. The average parasitism was 36.96% with the highest adult emergence of 83.09% at pod and lowest (78.92%) at leaf stage. The mean parasitization time was longer on Bulbul-98 compared to mixed crop and Toria-A. The developmental time of aphids increased with severity of water stress on both the host plants with a trend of shortest to longest period from field capacity to 50% field capacity. The fecundity of L erysimi was the highest (65.68 nymphs/aphid) at field capacity that decreased to 43.76 nymphs/aphid with decrease in water supply. The intrinsic rate of increase (-1m) was inversely proportion to moisture levels and growth of turmip aphid. The aphids were smaller in size on UCD 310/3 (B. carinata) at 75% field capacity and at field capacity on Bulbul-98 (B. napus). An indirect proportion between aphid’s hind tibial length and moisture levels was observed. Both male and female parasitoids were larger in size at field capacity followed by 75% field capacity and 50% field capacity on susccptible genotype. The parasitism was lowest at 50% field capacity on Bulbul-98 and highest at field capacity on UCD 310/3 with a trend of 50%<75%< field capacity for various water levels. The adult emergence was higher at field capacity ehased by 75 and 50% field capacity on both the host plants. Similarly D. rapae grew faster at the field capacity followed by 75 and 50% field capacity: However, they developed in comparatively less time on UCD 310/3 compared to Bulbul-98 and highest at field capacity on UCD 310/3 with a trend of 50% <75%< field capacity for various water levels. The adult emergence was higher at field capacity chased by 75 and 50% field capacity on both the host plants. Similarly D. rapae grew faster at the field capacity followed by 75 and 50% field capacity; however, they developed in comparatively less time on UCD 310/3 compared to Bulbul-98 The row spacing by intercropping B. napus with wheat significantly affected the body size of L. erysimi and D. rapae among all the treatments. The aphids and parasitoids were smaller in size on sole brassica and alternate row of wheat and brassica (1W X IB) whereas. They were larger on two rows of wheat per row of brassica (2W X IB) and three rows of wheat per row of brassica (3W X IB). When more space was providedto L. erysimi, their body size increased significantly at the growth rate of 2.54 um per 21.0 cm. Highest percentage of parasitism and adult emergence of D. rapae were recorded in 3 W IB and minimum in sole brassica followed by 1W X IB and 2W X IB. The parasitoids developed in less time in case of 3W X IB followed by 1W X IB 2W X IB and sole brassica crop L. erysimi was larger in size at 4 aphids per plant followed by 8 and 12 aphids per plant. The hind tibial length of female parasitoids was more at the lowest initial population denisity and vice versa. The male parasitoids were large-size on moderate aphid population density followed by low and high population densities. The percent was highest at 800 and minimum at 2400 aphids per brassica box with identical pattern for the percentage in adult emergence. The parasitoids took more time to develop on dense aphid populations followed by moderate and low ones. A strong relationship between aphids and female parasitoids exited in field as well as in pot experiments. The regression among different moisture levels, percent parasitism of D. rapae, row spacing by intercropping and aphid’s population densities was strongly affiliated with the second and third trophic levels in terms of body size Agriculture &amp; Veterinary Sciences(a)2006University of Arid Agriculture, Rawalpindi;Department of EntomologyThesis

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