广州小斑螟发生与环境因子的关系

The relationship between Oligochroa cantonella Caradja and environmental factors

广州小斑螟是红树林的一种灾害性的食叶害虫。通过室内饲养和野外观察,对广州小斑螟的发生和环境因素的关系进行了详细的研究。结果表明,随着龄级的增加,取食量增大;在不同样地不同滩位的虫口密度差异性规律不同;在单株白骨壤的不同方位虫口密度差异显著,正南方向虫口密度最高,正西、正北虫口密度最低;在单株白骨壤的中上部明显高于下部;广州小斑螟大龄幼虫较耐水淹,水淹6 h的死亡率为0;不同地区温度的差异可导致广州小斑螟的发育进度的不同。

The morphological and biological characteristics of Oligochroa cantonella Caradja, a leaf-eating pest of mangroves, were studied by laboratory rearing and field observations. In the laboratory, food consumption increased with age class. Mature larvae consumed the greatest amount of food, especially the 4th and 5th instars, which consumed most of the food supplied for the entire period of larval development. It was concluded that the 4th- and 5th-instar larvae were most harmful, and emphasis should be given to the prevention and treatment of larvae before the 4th-instar stage, populations had a regular distribution, which is very different. In Shatian county, the population density on the inner bar was significantly greater than on the beach. In addition, differences in density were found between populations with different orientations and at different sites of Avicennia marina. The density of O. cantonella was greatest in south-facing populations, and in the middle and upper sites. This may be a tidal effect with the lower site of A. marina being flooded for longer than the upper site, which was only submerged at high tide. By contrast, in Dongwei county, the population density in the crown of A. marina was higher than that at the tide line. The population density in the middle site of A. marina was greater than that in the upper site, and the population density in the upper leaves of A. marina was more than that in the lower leaves. These results may be explained as follows. First, the larvae in the upper site of A. marina were easier prey for wasps and hornets. Second, the larvae of O. cantonella feed in the crown in the evening and morning, moving to the inner and middle-lower site of the crown during the day. In addition, the older larvae were more resistant to flooding, with no mortality observed even after 6 hours＇ submergence. After 8 hours＇ submergence larval mortality increased significantly, with 100% mortality being recorded in those larvae submerged for 12 hours. The results indicated that the larvae of O. cantonella were resistant to submergence and adapted to the intertidal environment. Finally, the developmental progress of O. cantonella was found to be influenced by temperature in different regions. Pupae accounted for about 50% of all the worm stages in Shatian county Beihai city, while the pupa of 0. cantonella accounted for about 47.1% of all worm states in Yuzhouping county Fangchenggang city. The overall developmental time of O. cantonella in Fangchengang city lagged 5---7 days behind that in Beihai city.