Biology, Ecology And Chemical Control Of Oblodiplosis Robiniae Haldemann

Robinia pseudoacacia has been one of the native species since introduced from America in the end of the 19th century. It has played an important role in wind and sand, water and soil conservation, afforestation of barren hills and Landscaping. But Oblodiplosis robiniae Haldemann has done serious harm to it in our country. Oblodiplosis robiniae Haldemann is one of important invasive insect pests newly discovered and reported in 2006 in china which falls under the class of Cecidomyiidae of Diptera. Native to North America, one characteristic of this species attacking leaf of black locust tree is infestation. It has posed a serious threat to ecology, economy and society of the black locust forest. We should conduct in-depth study on the biology and management of technology of Oblodiplosis robiniae Haldemann for its control.In this paper, the biology, ecology and chemical control of Oblodiplosis robiniae Haldemann were preliminarily studied both in field and in the laboratory.This result offers the effective control measures. The main result of study is as follows:1 Morphological characteristicsThe eggs of Oblodiplosis robiniae Haldemann is circle, pale-yellow, the length (0.32±0.01) mm, the maximum width (0.12±0.02) mm.The larvae just hatching is oval, the body transparent and soft, the length (0.33±0.03) mm and the maximum width (0.12±0.01) mm.The larvae is 3~4 instars and the overwintering mature larvae cocooned in the soil.The color of the cocoon is gray, the length (2.67±0.21) mm and the maximum width (1.45±0.20) mm. And the pupa is obtected.2 Biology of Oblodiplosis robiniae Haldemann(1) Oblodiplosis robiniae Haldemann have 6 generations in one year, and generation overlap. It overwinters with mature larvae cocooning in the soil.The overwintering generation adult become to emergence from the soil in first ten day of April of next year. And the mature larvae become overwintering in the soil from the gall. The research on overwintering generation adult emergence period suggested that the eclosion peak appeared in the middle and late ten days of April. The reseach in the laboratory suggested that the eclosion peak appeared in 08:00 and 18:00 and the hatching peak in 04:00 and 20:00 each day.(2) We determined adult longevity and oviposition of Oblodiplosis robiniae Haldemann in different temperature in the laboratory. At the range of 18℃to 34℃, adult longevity and oviposition of Oblodiplosis robiniae Haldemann shortened with the temperature increasing. The average fecundity one female adult ran to the peak at 26℃, 43.33 eggs.(3) In the laboratory, we feed adult of Oblodiplosis robiniae Haldemann with different sophorae honey and sugar concentration and found that the female longevity was prolonged by supplementary nutrition, separated in the concentration of 5% and 1%, but the male not. The affect of 5% sophorae honey concentration and 1% sugar concentration have significant affect on adult longevity and oviposition.3 Ecology of Oblodiplosis robiniae Haldemann(1) We determined the developmental duration of larvae and pupas in different temperature in the laboratory and fond that they were related significantly to temperature. At the range of 18℃to 34℃, the developmental duration of larvae and pupas shortened with the temperature increasing. And we calculated the thermal threshold and the effective accumulated temperature for the development with the Least Square Method. The thermal threshold of eggs and pupae is 8.90 and 9.28℃and the effective accumulated temperature is 41.10 and 88.01 day degrees.(2) For the first time we found that the overwintering mature larvae cocooned in the soil, mostly in 0~3㎝ and the space distribution was aggregated. We surveyed the larvae density at different levels and directions of the tree in spring, summer and fall shoot period. The result was the larvae density of the upper significantly higher than the middle and the lower and there was no significant difference among the east, south, west and north.(3) The investigation of population dynamics of the larvae from April to September suggested that the harm of the larvae began from the middle ten days of April, reached peak in middle ten days of June and end in middle ten days of September.4 Chemical control(1) The selective toxicity of three kinds of insecticides to the larvae of Oblodiplosis robiniae Haldemann was determined in the laboratory. The LC50 of chlorbenzuron, imidacloprid andchlorpyrifos is 90.6499 mg/kg, 10.0682 mg/kg and 74.9488 mg/kg.(2) Soil treatment with 40% chlorpyrifos EC of three concentrations, the effect was significant. Among them, 500 x of 40% chlorpyrifos EC is best, reached 100%.(3) Prevention and treatment efficacy of three kinds of insecticides in early and mature gall period suggested that the effect in early gall period was significantly better than that in mature gall period.