The Damage And Ecological Characteristics Of Tomato Russet Mite Aculops Lycopersici (Tryon)

The tomato russet mite Aculops lycopersici (Tryon) was first found in America in 1892 and was described by Australian scholar Tryon in 1917. In China, it was first reported in Guangxi in 1980. From then on, it was found in Shanghai, Hebei and other provinces. In China there was little research on habits of A. lycopersici,and on the physiological and biochemical responses of tomato injured by A. lycopersici. The author investigated the distribution and formation of the injury of A. lycopersici on tomato plants, proposed the concepts of injury grading standards and individual (or district) severity of damage (DS), the unit area of mites (UA) and calculation formula. After systematic investigation of the performance of tomato russet mite in fields, we built a better affected model and control threshold of the tomato russet mite by using statistical analysis and calculus. Through researching the relationship between varieties and tomato russet mite, we also set up experimental population life table on different varieties, selected three resistant varieties and explored the resistance mechanisms.1.Under mite pest damage, plant growth and development indicators such as height, diameter, leaf area, green leaves, branches, the highest fruit branch affected to varying degrees. Our study shows that:there was significant difference in plant height and diameter between the different harm levels. Different degrees of damage demonstrated different loss rate, and a period of time will play a minor role in compensating the injured plants. However, when the damages were too serious, crop finally had yield loss because the compensated yield did not surpass the damage by mite itself. Loss of leaf area is the main reason leading to yield decrease. The loss of leaf area per plant is composed of two components, namely, the loss of single area and reduction of the number of green leaves. Single area lost is mainly affected by inhibiting the growth of leaves and premature cessation of growth. Green leaves decrease was caused by the reduction of the numbers of highest branch and branches. 2.Chlorophyll and soluble sugar contents were measured of different damage levels. Regression model of the loss of chlorophyll (CHL) and soluble sugar growth rate (SCI) were established on injured level.CHL=11.247DD-1.211±0.1198 R²=0.985SCI=exp (0.6487DD-1.8563)±0.0194 R²=0.992Soluble sugar and Vitamin C contents were measured at different damage levels. There was a significant reduction in tomato soluble sugar content when damage degree is two compared to control regional. There was a very significant difference in Vc content at three levels compared with the control regional at the 0.01 level.3.There would be a centre plant after the mites moved into field; therefore, the distribution in field was a type of aggregated distribution. According to the injury of the process of single leaf, the severity of the damage (DS) is divided into six basic levels: DS= (∑DiSi/∑Si)/n.We described the relationship between population and the temperature and rainfall. There was one peak for the population in open fields and were two peaks for that in greenhouses. The difference between the two populations lie in: (1) the time leading to peak was shorter in the population of green house (about 15 days) than that of open field (about 30 days); (2) the mite population density at peak stage was higher in greenhouse than that in open field. The population dynamics of A. lycopersici showed a trend of moving from the early low leaf to higher leaf in later season. In the first four weeks an average speed was one leaf per week and then speeded up at a speed of three leaves per week. On the basis of the biophysical characteristics of A. lycopersici, GIS was applied to analysis the adaptive distribution of A. lycopersici in China. It has been found that most area in China is adaptive for A. lycopersici, especially the South China, which is in a high risk of A. lycopersici invasions. Some area in East China and Middle China are also the adaptive area of A. lycopersici. Actions must be taken to prevent A.lycopersici from invasion into these regions.4.The concent of "Cumulative severity of damage" were proposed and successfully explained different loss of production in different ecological conditions. The economic threshold of the mites was decided for the population in Minghang (2007):ET_DS=0.034 (on injury level);ET_CDS=1.956 (on cumulative severity of damage) and ET_LD=9.8065.Development of tomato russet mite A. lycopersici on 12 tomato strains (the more hair ones YZ618, YZ619, the less hair ones YZ419, YZ507, YZ504, the wild ones YZ7, YZ5, the yellow-leaf ones YZ401, the conventional ones YZ406, YZ412, YZ413, YZ515) were studied in the field and laboratory. The results indicated that there were significant differences in population density of the mite on different tomato strains, with that on YZ504, YZ507,YZ419 higher, and that on YZ7, YZ618, YZ619 the lowest. There were also notable discrepancies in livability, developmental duration, egg production and other examined parameters of the mite on different strains in the laboratory: the egg production was the highest on YZ504, second highest on YZ507 and YZ419, the lowest on YZ7, and the ovipositional number on YZ504 was the biggest, second biggest on YZ507 and YZ419, the smallest on YZ7. Judged with the life parameters of the experimental populations of the mite, YZ7 and YZ618 were tomato strains resistant to the mite while YZ504, YZ419 and YZ507 were susceptible to the mite.6.The investigation of the correlation between the physical and chemical characters of three tomato varieties and A. lycopersici was carried out in the lab. Results showed that mite's amount on the multi-hair plants YZ618 was significantly less than YZ504 and YZ413. Mites inhabited on different parts of three tomato varieties, rare mites were found on the upper part of YZ618, and the amount of mites parasitized on the upper part of YZ504 was obviously more than the middle and lower part, while more mites were discovered on the upper and middle part of YZ413. The enzyme activities of polyphenol oxidase (PPO), peroxidase (POD) and ascorbic peroxidase (ASP) in leaves increased after infested by mites and the mite-resistant YZ618 was more sensitive. The correlation analysis indicated that PPO was the mite-resistant biochemistry factor induced by the mite infection, and ASP was the original mite-resistant biochemistry factor.However, there was no significant relationship between SOD and mite-resistance.