The Study On The Virulence Variation For Plutella Xylostella In Different Species Of Hosts

In this research, the diamondback moth (Plutella xylostella L.) was studied in the ecological system. By the long-term feeding with six different cruciferous vegetables and host shift treatments, the food consumption, the amount of fecundity, the level of acetyl cholinesterase esterase and the activity of carboxylesterase in diamondback moth were observed. Based on the data collected, the adaptability to different host, the virulence variation as well as the distribution law of diamondback moth were analyzed. My study provides the theoretical supports to the proper redistribution of rational vegetables and the control of diamondback moth in regional vegetable ecosystems.The results can be concluded as:1. Significant difference was observed among six host plants consumed by diamondback moth. The order of food consumption changes to different species of host plant, from large to small, is: mustard greens>Chinese cabbage>Chinese flowering cabbage>carrot>Chinese kale>cabbage. In field, a variety of vegetables are available, which may be the reason for diamondback moth rampancy.2. Fecundity sizes of diamondback moth are not different in significance by treating with six different host plants. A more obvious reducing trend was observed in fecundity size by feeding diamondback moth with radish. The less obvious decreasing trend was also observed in mustard greens and kale as well.3. Changes in the level of acetylcholinesterase activity of diamondback moth follow the order: mustard greens> Chinese cabbage >carrot > cabbage> Chinese flowering cabbage > Chinese kale. But the difference is less significant than that of carboxylesterase activity. The changes exhibit a decreasing trend in treatments with mustard, Chinese cabbage, kale and cabbage; while in radish treatment, the acetylcholinesterase level changes in an increase-decrease wave-shaped pattern. The esterase activity in diamondback moth changes as following: mustard greens> carrot > Chinese cabbage > Chinese flowering cabbage> cabbage> Chinese kale. The mustard shown the most significantly positive effect on diamondback moth, which increased from 0.6070 to 0.6930; cabbage has a negative effect on diamondback moth, with the value decreased from 0.5577 to 0.5210. It indicates that the enzyme activity and turnover rate can be regulated differently by various host plants.4. With host shift, the food consumption of diamondback moth responds differently. In the host shift from mustard, Chinese flowering cabbage, Chinese cabbage, radish and cabbage transferred to Kale, the food consumption changes are more obvious. The change is not significant during the shift from Chinese flowering cabbage or Chinese cabbage to mustard.The changing pattern of acetylcholinesterase activity exhibits inconsistently with host shift. In short-term feeding conditions, the increasing trend was observed in host shifts from radish to mustard, or from Chinese cabbage to other host plant. The long-term feeding treatment showed different trends in both direction and rate of acetylcholinesterase activity. The changes of carboxylesterase were more significant in host shift experiments, indicating that the pesticide susceptibility can be impacted by host shifts treatment.