Title of Thesis

Investigations on Chrysoperla Carna (Stephens) (Neuroptera: Chrysopidae") as biological Control Agent Against Cotton Pests

Author(s)

Muzammil Sattar

Abstract
Studies on effect of different hosts on biology of Chrysoperla carnea (Stephens) carried out under laboratory conditions at 26±2°C and 65±5% R. H. indicated that the incubation period of eggs of C. carnea females feeding on different hosts as larvae was significantly (P <0.001) different from each other. The order of larval period on different prey species was Sitotroga cerealella > Aphis gossypii > Phenacoccus solenopsis > mixed host diet > Pectinophora gossypiella > Helicoverpa armigera.The maximum (100%) and minimum (50%) survival to adult stage was recorded on S. cerealella and P.gossypiella as hosts. The highest fecundity per female (503.3±9.17) and fertility (85.61±0.68) of eggs were recorded for females reared on S. cerealella eggs as a larval diet. C. carnea larvae consumed maximum amount of food when feeding on S. cerealella eggs followed by A. gossypii. The insects reared on artificial diet laid more eggs which were significantly more fertile than the eggs of insects feeding on S. cerealella. Survival to adult stage was also significantly higher for those insects feeding on artificial diet as larvae. Larval density had significant (P <0.001) effect on larval and pupal duration, pupal weight and percent adult emergence. When C. carnea was reared on different temperature regimes, 26°C was found to be the optimum temperature regime with significantly higher pupal recovery, adult emergence, fecundity and fertility of eggs. Experiments conducted at lower temperature regimes for extending the shelf-life of C. carnea indicated that duration of storage and temperature significantly affected egg survival. No egg survived when stored at 5°C. Egg stored at 7 and 9°C had 66.0 and 71.52% survival and all eggs were killed when stored for more than one week. Lower temperature had negative effect on survival of first instar C. carnea. Second and third instar C. carnea larvae showed better survival at lower temperature during storage compared with first instar. Compared with eggs and larvae, pupal stage of C. carnea was more sensitive to lower temperature regimes. Duration of storage and temperature adversely affected fecundity of females and fertility of eggs.
Larval mass-rearing methods indicated that rearing of individual larva in plastic tubes yielded highest larval survival and percent adult emergence compared with other two methods. Different concentrations of various proteins in the artificial adult diet of C. carnea had a significant (P <0.001) effect on fecundity and fertility of eggs. The highest fecundity (785.12±25.75) and fertility (89.23±0.36) of eggs was recorded for adults feeding on diet containing Nu lure (5.0 ml diet-1). Among all colours tested, C. carnea females preferred black colour as a substrate for egg-laying and laid the highest (91.00%) eggs. C. carnea laid highest number of eggs when a sex ratio of 1: 3 (male: females) was maintained. Radiation of C. carnea larvae and pupae affected the biological parameters. Larval period were extended when larvae were irradiated as first, second and third instars at 5 Gy. At higher dose levels, the biological parameters were affected negatively. Toxicity of insecticides against eggs of C. carnea varied significantly. Spinosad was non-toxic causing no egg mortality, abamectin was slightly toxic causing 2.5% mortality, while methomyl was highly toxic insecticide causing 26.25% mortality at field application dose rate. When C. carnea larvae and adults were exposed to insecticides, methomyl was found the most toxic and spinosad the least toxic insecticides.
C. carnea egg cards were released in cotton (cv. NIAB-78) field for population management of sucking insect pests. Aphid, Aphis gossypii population reduction in predator released treatments was significant (P <0.001). By the end of season predator was able to cause 76.13 and 75.02% population reduction of aphid during 2005 and 2006, respectively. Release of C. carnea cards in cotton crop significantly (P <0.001) reduced the population of jassid, Amrasca devastans; thrips, Scirtothrips dorsalis and whitefly, Bemisia tabaci. The level of population reduction varied between different pest species. Population reduction was 83.70 and 76.07% for jassid; 37.59 and 60.32% for thrips and 51.84 and 44.08% for whitefly during 2005 and 2006, respectively. Release of C. carnea egg cards also had a significant effect on resident population of C. carnea in predator released treatments compared with control treatments. When C. carnea larvae were released in field cage study, third instar larvae were significantly (P <0.001) more effective than first and second instars in reducing sucking insect pest population in cotton.

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