| Ophraella communa (Coleoptera:Chrysomelidae) of North American origin is a recently recovered herbivorous insect in China mainland, which defoliates alien invasive ragweed Ambrosia artemisiifolia (Compositae) at both larval and adult stages. This insect only attacks ragweed, but occasionally was found on Xanthium canadense, a plant that is closely related to ragweed, A. artemisiifolia. It is accordingly considered as a potential biological control agent to control ragweed in some areas, where ragweed is being grown to rear the insect and then released into the field. Artificial diet has numerous advantages over the plant-feeding method in mass production of biological control agents. The thesis was designed to study semi-artificial diets of O. communa, so as to efficiently mass-produce the biological control agent.1. A preliminary study on semi-artificial diets for O. communaBased on the semi-artificial diets for other leaf beetles (Chrysomelidae), the orthogonal experimental design was employed for 19 factors at mixed levels (L32(45×216)) in this study. Eight main components for adult survival were obtained, including wheat-meal,10%KOH, dextrose, menthyl-p-hydroxybenzoate, Ambrosia plant powder, agar, cholesterol, and soybean oil. Eight main components for the 2nd instar larval development were obtained, including rolled oats, agar, wheat meal, dextrose, choline chloride,10% KOH, water, and soybean oil. The results form a basis for further study of the artificial diet of O. communa.2. Assay for main nutrition ingredientsof A. artemisiifoliaNutrition ingredients of the host plant was assayed, including soluble sugar, soluble protein, VC, ash content, pH, and water content. The results are following:soluble sugar 1.43±0.01 (%), soluble protein 43.97±0.58 (mg/100g), Vc 18.73±0.81 (mg/100g), ash content 14.49±0.23 (%), water content 85.15±0.16(%), PH volume 8.20±0.09, leaf mass density 0.32±0.01 (g/cm2), leaf density 1.23±0.22 (g/cm3).3. Feed testing with different formulae of semi-artificial dietsDesigning the semi-artificial diets formula, respectively according to the main nutrition ingredient content of the ragweed, the ragweed leaf meal content in the semi-artificial diets, several known semi-artificial diets formula of Galercinae insects. It is concluded that dietd formulae No.6 and No.14 were better than others for adult.:The life span of adult fed with No.6 diet and No.14 diet were 22.51±0.87 days and19.54±1.05 days,respectively, and eggs were laid.One larva of second instar was successfully reared to adult by No.14 diet.4. Effect of the juvenile hormone analogue ZR-512 on life-span, oviposition and body weight of O. communaExperiments were conducted to examine effects of the juvenile hormone analogue ZR-512 on the life-span, oviposition, and body weight of the adult leaf beetle. The result showed no significant effects of the juvenile hormone analogue at different concentrations on longevity, but some influences on body weight and oviposition. O. communa reached heavy weight at 0.05ug per individual and laid eggs to maximum at 0.Olug per individual after receiving the juvenile hormone analogue. The average hatching rate of eggs laid by adults receiving the hormone treatment was significantly different compared to the control group, suggested that the impact of juvenile hormone to egg hatching rates was not significant. |
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