| The green peach aphid Myzus persicae (Sulzer) is one of the most common pests of agricultural crops and vegetables in the greenhouse as well as in field crops. M. persicae feeds on plant phloem, causing water stress, wilting, and reduces growth rate of the plant. Its continuous infestation causes substantial yield loss. For controlling of this important pest indiscriminate use of insecticides is practiced which is not only health hazardous and environment pollutant, but also it cause aphids develop resistance against pesticides.Aphids reared on artificial diet can facilitate the studies on nutritional physiology which will help to evaluate the impact of insecticidal substances on aphids as well as natural enemies. It will be ultimately helpful for the mass-rearing of natural enemies. Natural enemies plays vital role to manage the various insect pests including aphids and they are environmentally safe and their effects are long lasting. Variety of predators and parasitoids are released for suppression of variety of pests. Among them green lacewing, Chrysoperla sinica (Tjeder) (Neuroptera: Chrysopidae) is one of the most effective and prolific predators of several insect pest species such as aphids, jassids, thrips, leafhoppers and mites that is distributed throughout China. Extensive studies have been carried on this predatory insect. Therefore it has been mass-reared on natural as well as artificial diets. Chrysoperla sinica reared on artificial diets resulted prolonged developmental duration, reduced survival rate, lower fecundity and adult longevity as well. Those factors could limit its application extensively. Therefore we screen out the suitable pH value of artificial diet for green peach aphid in this article; then we fed C. sinica with artificially reared green peach aphid to observe developmental period, nutrition content and enzymatic activities. Moreover, we also determined the ability of 3rd-instar green lacewing to control green peach aphid. We offered both artificially and naturally reared aphid to chrysopid laravae to assess intraspecific competition. The results are briefly discussed as under.1. In this part of experiment we investigated survival rate, reproduction and antioxidant enzyme activities of M. persicae on the artificial diet with different pH values. In order to determin the optimal pH value of artificial diet for M. persicae. The aphids feeding on the diets with different pH value were significantly different in survival rate after 3 days. The highest survival rate and intrinsic rate (rm) of diets were recorded on 7.0 pH. The fecundity and intrinsic rate were 36.62 and 0.159. The activities of superoxide dismutase (SOD) and catalase (CAT) in all treatments increased significantly as compared with the control which reached the maximum within 24h, and then declined. During the investigation, the antioxidant enzyme activities of pH 7.0 and pH 7.2 slightly changed, and recovered after 48h to near normal level. Results showed that pH= 7.0 was suitable diets rearing for green peach aphid.2. In this part of experiment C. sinica was fed with M. persicae, which reared on artificial diet, rape seeds as well as soybean aphid. We determined their effects on preimaginal developmental, reproduction, nutrient contents and digestive enzyme activities. The results depicts that degeneration and regeneration were observed when C. sinica reared on green peach aphid fed on artificial diet (CGAD) for three generations. In third generation development of CGAD was significantly longer when 3rd-instar larvae were fed with M. persicae reared on rape seed. Furthermore, pupal weight of C. sinica was also significantly lower when it consumed M. persicae, reared on rape seed and soybean aphid as well. The overall preimaginal developmental period was not significantly different in all three treatments. Larval survival rate was higher when chrysopid larvae were fed with Aphis glycines Mastumars. The fecundity of CGAD was slightly lower but no significant differences were observed as compared to C. sinica fed with A. glycines. Total carbohydrate content of M. persicae reared on artificial diet was significantly higher than, A. glycines. Trehalase activity was significantly higher than all other treatments; it was 1.2 and 1.37 times higher in M. persicae reared on rape and A. glycines, respectively. Although the negative effects for growth and development of CGAD were observed, the total developmental duration of larvae, larval survival rate, emergence rate, pupal duration, preimaginal developmental duration and longevity of adult were no significant differences between CGAD and 2 controls. There were no significant differences in adult fecundity of CGAD and other treatments except the third generation of CGAD, so this method could be feasible for mass-rearing of green lacewing.3. The consumption of aphids by all the instars of C. sinica larvae was increased as number of aphids increased which followed a negatively accelerated growth curve. It was consistent with the mode of Holling typeâ…¡functional response. And the functional response model of CGAD was Na=0.5870Nt / (1+0.0007Nt). The attack coefficient of CGAD was 0.5870, and its handling time was 0.0012. It was significantly lower than C. sinica reared with green peach aphid and soybean aphid. As larval age of C. sinica, increased its ability of attack increased and the handling time shortened. The number of aphids preyed by 2nd or 3rd instar larval was greater than 1st instar. Theoretical maximum daily predation rate of green peach aphid by CGAD was 848.1. So green lacewing reared by this method can control M. persicae effectively.4. Intraspecific competition of 3rd-instar larvae showed that, as the numbers of larvae increased, the searching efficiency reduced. When 250 M. persicae were offered, with 3rd instar larvae of C. sinica increased from 1 to 5, its searching efficiency of CGAD was reduced from 0.35 to 0.16, respectively. The factor of intraspecific competition was 0.49, it was the most competitive in the three treatments. When 5 larvae of lacewing were kept in a Petri dish, the competition intensity of CGAD was increased significantly, the factor of competition intensity was 0.54, while the treatment of green peach reared on rape seed was 0.48. So we should consider the damage aphids caused when using this method to control aphids, and release the amount of green lacewing properly to avoid cannibalism.
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