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Authors: Nadeem, Sajid
Keywords: Applied Sciences
Agriculture & related technologies
Animal husbandry
Issue Date: 2010
Abstract: Present studies were conducted to improve production and storage extension of Trichogramma chilonis (Ishii), Chrysoperla carnea (Stephens) and their hosts for effective field releases against major insect pests of cotton. Different experiments comprised; the rearing of laboratory host, Sitotroga cerealella (Olivier), the impact of radiation on the shelf life extension of its eggs, storage of parasitoid (T. chilonis) and predator (C. carnea) at low temperatures, the searching ability of parasitoid under field conditions, evaluation of the field releases methods for parasitoid and predator and their field adaptations and effectiveness against target pests in the cotton. Development and evaluation of the rearing of S. cerealella on its naturally available cereal foods, like maize, barley, sorghum and wheat revealed that the rearing of S. cerealella was as equally good on sorghum and barley as compared to wheat grains. Whenever, the rearing of healthy and heavy sized adults were required, the rearing on maize showed good results but with reduced fecundity and prolonged life span. The parasitism by T. chilonis on the gamma irradiated eggs of S. cerealella was successfully achieved at the dose of 50 Gy up to 7 days. The cumulative effect of radiation and low temperatures on the storage of host eggs at 6, 8, 10, 12, 14 and 16 o C from 5 to 90 days showed non-significant effect as compared to their individual effects. Storage of host, S. cerealella eggs at 6 o C for 5 to 50 days was a comparatively more suitable for both short and long durations, however, host eggs stored at 10, 12, 14 and 16 o C proved good only for short term duration. Storage of the parasitoid, T. chilonis at a temperature of 10 o C, proved to be effective for highest percent emergence, percent parasitism and adult longevity. Among different concentrations of honey as adult food, its 10% solution showed best results for male and female longevity and other biological parameters, however, reduced longevity was observed with increased in concentration of honey solution. The optimum rearing temperature for T. chilonis was found to be 28 o C at which developmental period was optimal; parasitism, adult longevity and emergence of T. chilonis from host eggs were higher as compared to other temperatures. Storage temperature of 8 o C seemed to be optimum for C. carnea eggs for 20 days with minimum xxiidetrimental effects on developing embryo inside the egg. This temperature (10 o C) was almost good for short term (20 days) and long term (40 days) storage durations. Moreover, reproductive parameters of C. carnea adults remained good up to 90 days storage of eggs at this temperature. The impact of different rearing temperatures on the developmental and reproductive parameters of C. carnea proved best at 25 o C. Host eggs of Plodia interpunctella and S. cerealella showed no differences upon the quality of developmental traits of T. chilonis and C. carnea, and both hosts showed comparable results for rearing. Evaluation of the field releases of parasitoid T. chilonis, through different methods inferred that micro-cages not only increased the releases and parasitism but also protected the parasitoids from unfavorable environmental conditions. Evaluation of C. carnea releases in the field showed that the releases of larvae were having more survival as compared to the releases in egg form. Therefore, it is suggested that predator should be released in the larval form to get more consistent field results. Parasitism by T. chilonis on host eggs at different distances under the field conditions revealed that the searching ability and parasitism were gradually decreased as the distance increased from the place of release. Survival of T. chilonis and C. carnea under field conditions varied according to the prevailing environment of the field. Comparative evaluation of the bio-control agents (T. chilonis and C. carnea) in management of Helicoverpa armigera, Earias vittella, Bemisia tabaci, Thrips tabaci and Aphis gossypii in cotton under natural field conditions during the years 2007 and 2008 exhibited that integration of bio-control agents, enhanced the suppression of these pests as compared to the untreated control.
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