| Lycium barbarum is particularly vulnerable to pests and diseases for the reason that its vegetative growth and reproductive development are at the same time. There are five main pests in the main wolfberry producing areas in China, which are Paratrioza sinica, Aceria pallida, Jaapiella sp., Aphis sp. and Psilothrips indicus. With the increase of L. barbarum cultivation, the damage caused by pests becomes more and more serious. So far the prevention and control of wolfberry's pests have been mainly dependent on chemical pesticides. However, for the long-term, frequent and vast using of pesticides, the problem of pesticide residues has become one of the most important handicaps to China wolfberry industrialized development. Therefore, the field production needs safe and effective control technique to improve the quality of wolfberry.Bionic glue and defoliant are new physics methods to prevent and control pests instead of using chemical pesticides.This thesis made a comparative analysis to the effects of different treatments on the population dynamics of pests and their natural predators, and the number of buds and fruit according to the field experimental results in Zhongning county of Ningxia Province. The main results were as follows:1. Effects of different treatments on the main pests' population dynamics of L. barbarum: During mid-April to late-June, the excessive growth of P. sinica, Aphis sp., A. pallida and Jaapiella sp. was brought under effective control with the help of bionic glue in bionic glue treatment, but the control effect on P. indicus was not so good. In mid-July due to the degradation of bionic glue, the damage caused by P. sinica, and Aphis sp. increased rapidly. In late July, spraying defoliant could reduce the population of P. sinica, A. pallida, Aphis sp. and P. indicus rapidly to zero, but for Jaapiella sp., which larvae had emerged from gall and drilled into hidden places, it was invalid. Frequent spraying chemical pesticide had excellent control efficacy to P. sinica and Aphis sp., but the control effect to the pests, which lived in hidden places such as Jaapiella sp., A. pallida, and P. indicus, was ineffective. The trees in control treatment was damaged seriously by P. sinica and Aphis sp., for the reason that the place had little human disturbance. The outbreak of P. sinica and Aphis sp. caused the defoliation of leaves and weakened the growth of L. barbarum seriously, and the population growth of Jaapiella sp., A. pallida, and P. indicus was restrained.2. Effects of different treatments on the main natural enemies' population dynamics: During mid-April to late June, bionic glue had been sprayed three times in bionic glue treatment, which brought some bad influence on the egg production of Chrysopa initima. With the degradation of bionic glue, the influence waned gradually. In late July, the population of Monodontomerus sp. grew rapidly. As bionic glue has been degraded seriously, there were little influence on its population. Compared with pesticide, bionic glue was helpful to conserve and utilize Monodontomerus sp. In late July, with the help of defoliant, old leaves were replaced by new young leaves, which could attract more adult C. initima to lay eggs. As we didn't do any treatment after spraying defoliant, the population of Monodontomerus sp. grew rapidly, compared with pesticide treatment. However, pesticide had little influence to C. initima. In control treatment, the number of C. initima and Monodontomerus sp. was lower than the others. That was because nylon net, which was covered in the outside of control treatment, prevented natural predators from entering.3. Effect of different treatments on the number of fruit:During mid-April to mid-June, compared with pesticide treatment, bionic glue treatment had more fruit at boom bearing period. As the stickiness of bionic glue lost gradually, the number of pests grew rapidly, resulting in poor fruit growth. However, after spraying defoliant, the population of pests in bionic glue and defoliant treatment, and pesticide and defoliant treatment decreased rapidly and new leaves sprouted quickly, which were beneficial to the growth of buds and fruit. In pesticide treatment, frequent spraying pesticide suppressed the pest growth significantly. So fruit growth was protected from damage. Nevertheless, there were no treatment after early August, which caused the damage of A. pallida growth. Therefore fruit growth was adversely affected. In control treatment, pest damage was so serious that tree vigor got untimely weakened, and the quality and yield of fruit were affected seriously.4. Effect of defoliation treatment on the number of leaves:In late July after defoliation treatment, leaves fell off quickly and absolutely.24 hours later after spraying defoliant, defoliation rate reached to 84.5%. A week later, a lot of new leaves came out quickly. In mid-August, the number of new leaves was found to be 1.95 times than that before spraying defoliant. In late August, huge amounts of buds came out. Defoliation treatment could not only accelerate the old leaves loss, but also promote new branches and buds formation. |
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