Effects Of Scirtothrips Dorsalis Hood Damage On Ginkgo Biloba L. Growth, Physiological And Biochemical Characteristics

Yellow tea thrips, Scirtothrips dorsalis Hood, also known as tea thrips, belongs to Thysanoptera, Thripidae. It is one of the most important leaf-eating insects to Ginkgo biloba L. .The main hosts are tea, peanuts, strawberries, grapes, mangoes. Outbreak in 1989. The author observed the morphological features indoor and set up in different densities, and effects of infesting in different S. dorsalis densities and damaged different days on plant growth, physiological and photosynthetic index of G. biloba were studied. The major results were listed as follows:1 Effects of infesting in different S. dorsalis densities on the plant growth of G. bilobaIn this section the leaf area, the fresh weihgt of unit area, the length of new wattle, the width at base of new wattle were studied. In these 4 indexes the thrips damaged fresh weight per unit area of greatest, followed by the length of new wattle, the leaf area, the width at base of new wattle of the smallest impact.After damaging 40d, five groups of the leaf area with the growth rate are 8.0%, 5.2%, 3.6%, 2.8%, 1.9% respectively, the latter 4 groups between the treated and control are significant differences, the 15/leaf and 20/leaf groups are no differences. The growth rate of the length of new wattle respectively, are 18.1%, 11.5%, 5.8%, 0.8% -0.8%, the first 4 groups were significant differences, 15/leaf and 20/leaf are no difference; new wattle growth rates are 13.8%, 4.5%, 4.9%, 3.0%, 0.9%, with the exception of 5/leaf and 10/leaf are no differences, other groups are significant differences; new wattle base diameter increased by 2.0%, 1.1%, 1.4%, 0.7%, 0.3%. In addition to 10/leaf processing, control and other groups are significant differences(p≤0.05). 2 Effects of infesting in different S. dorsalis densities on the physiological index of G. bilobaEffects of infesting in different S. dorsalis densities and damaged days on physiological index of G. biloba leaves were determined. The results suggested that, compared with the control, chlorophyl, soluble sugar and soluble protein were all reduced slowly, decreased by 48.9%, 37.3% and 33.3%, respectively, after damaging 40d with the insect densities of 20/leaf. During infest period, the content of tannin showed a dramatic decreases with a 50.7% reduction after infesting 10d with the insect densities of 20/leaf. While the content of tannin increased in different degree with the rising of the thrip densities after infesting 20d.3 Effects of infesting in different S. dorsalis densities on the photosynthetic index of G. bilobaIn this section photosynthetic index of G. biloba were stuied. After damaging, the photosynthetic rate, stomatal conductance and transpiration rate were reduced, intercellular CO2 concentration has increased. After damaging 10d ,there are significant differences in photosynthetic rate and stomatal conductance; after damaging 20d , there are significant differences in transpiration rate ; after damaging 30d, there is significant differences in intercellular CO2 concentration .After damaging 40d, the photosynthetic rate, stomatal conductance and transpiration rate decreased by 63.3%, 58.5%, 55.5%; intercellular CO2 concentration, as compared with the control with an increase of 2.8%, 8 %, 10%, 20%.Four photosynthetic indicators, the greatest changes in photosynthetic rate, intercellular CO2 concentration in the changed smallest.