Study On The Occurrence And Forecast Of Main Vegetable Pests And Diseases In Wenzhou

In recent years, with the adjustment of agricultural structure, the vegetable area in Wenzhou is increasing year by year. The annual planting area of vegetables amounts to more than110million. Since the wide variety of vegetables and rapid changes of cropping seasons, the occurrence of pests and diseases is very complex, thus being the main limit for the development of vegetable industry. Therefore, we investigated the occurrence and forecast of main vegetable pests in order to accurately guide the farmers to reduce dosage of chemical pesticides and mitigate environmental pollution, thus making the agricultural production more environmental. In this study, we studied on the occurrence and life cycle of Diamondback Moth, Spodoptera litura Fab. Spodoptera Exigua and Maruca vitrata (Fabricius) by the combination of indoor rearing, field cage, field observations, and trapping tools. In addition, we determined the physiological characteristics of Botrytis cinerea and Pseudoperonospora cubensis by means of observing the changes of humidity and temperature in greenhouses and investigating the disease progress periodically. Following are the main results obtained in the present study:1. The occurrence and life cycle of Diamondback Moth, Spodoptera litura Fab. Spodoptera Exigua and Maruca vitrata (Fabricius) were investigated. A natural population life table of Spodoptera litura Fab was set up. Different generations showed different insect mortalities. In addition, the population trend index, periods and causes of death in the key pesta were analyzed. The developmental threshold temperature and effective accumulated temperature of Maruca vitrata (Fabricius) were also determined.2. The spatial distribution pattern and sampling technique of Spodoptera litura Fab. were established, and so were Spodoptera Exigua. The spatial distribution pattern of Spodoptera litura egg mass was uniform in all of its spatial distribution. Young larvae showed a high degree of aggregation. After proliferation, the accumulation degree of old larvae declined. Overally, while the larval instars were large, its spatial distribution pattern tended to be evenly distributed from the aggregated distribution. Z-shaped and checkerboard were more effective for egg mass surveys. In contrast, pairs of diagonal and parallel line survey methods were better for young larvae, while Z-shaped was better for old larvae. Young and old larvae of onion Spodoptera Exigua distributed aggregately in the field, and the optimal sample was suggested.3、 Main factors that affected the field populations of the four insects were analyzed. We coule make a short-term forecast by calculating the developmental duration and effective accumulated temperature of the four kinds of insects, a medium-term forecast by combining the methods of investigating the pupa and the peak moth under lamp and estimating the spawning period of the circumstances. Furthermore, we were able to forecast the occurrence trend according to moth peak, and to forecast the amount of Spodoptera litura Fa. depending the population trend index.4. After the comparison of three pest forecasting tools, the new type of automatic-pest forecasting lamp,"Jiaduo", was chosen as the main tool for monitoring vegetable pests, because it was convenient and labor and time-effective.5. The physiological characteristics of Botrytis cinerea and Pseudoperonospora cubensis, and the major climatic factors favoring the occurrence of the diseases were determined. In addition, the reference factors for forecast and disease grading standards were proposed. Effective methods for forecast were also suggested.