| Batocera horsfieldi (Hope), considered as one of the most important stem-borer injurious insect in China, particularly attacks Fraxinus chinensisthatis regarded as a perfect species for greening in the coastal saline area. Actually, it becomes the main forest insect in Shouguang, Dongying and other city in Shandong province, and tends to spread. Studies in the spatial distribution, spatio-temporal variations and inter-ralationship with other tree species or plants of it in Fraxinus chinensis would be further illuminating the mechanism of outbreak and spreading. In addition, having a good knowledge of its biological and ecological habits, together with corresponding climate factors, will make a good performance in working out an effective control measures.Using geostatistics methods, we investigated the spatial distribution of Batocera horsfieldi (Hope) in three Fraxinus chinensis forest sites at different damage levels in the afforestation station, institute of forest science in Shandong province during 2013 to 2014. The study synthesizes the population of Batocera horsfieldi (Hope), local climate condition and environmental plants around forest. The results were: 1. The larvae preferred to concentrate in an area below 1 m (about 75%) from the bottom of the trees and increased with increasing damage levels above 1 m.2. Despite different models, Spherical, Exponential and Gaussian model, were fitted best to larvae spatial distribution in three kinds of infested forest, or in same forest in different year, the larvae was significant aggregation distribution, and the intensity of local spatial continuity was more than 64%.3. The year suffered the worst pest in 2013 whose population density was significant higher than any other years in all kinds of forests. The distance of spatial dependence of larvae was dropt down from 5.4-7.8 m in 2013 to less than 2 m in 2014, which indicated that the damage level fell down in 2014. It could be explained properly by climate conditions from June to August in different years:Appropriately higher temperatures would increase the population quantity and survival rate of larvae over winter while higher precipitations, or heavy rainfall events (>50 mm day-1) in the former year would perform the opposite.4. The spatial concentration location of the insect was changed between two years, which showed spreading trend that the insect spread from south to the north. However, the direction between the west and the east was not clear: the heavy damaged forest spread from the west to the east while the rests were opposite.5. The adults preferred Fraxinus chinensis in the stage of absorbing replenishing nutrition compared with other species, followed with wild rose(Rosa multiflora). But it was worth mentioning that the feeding amounts and life span of the adults would be higher under the mixed environment of those two species than each single condition. Therefore, the mixed environment in the stage of absorbing replenishing nutrition would change the spatial distribution of the insect and aggravate damage level to Fraxinus chinensis.The results indicated that the prevention of Batocera horsfieldi in Fraxinus chinensis should identify specific concentrated area and conduct integrated control pest measures (IPM), especially focus on the height below 1 m in damage forest. Climate condition and companion tree species also should be considered for making prevention and control measures in order to make prompt and proper adjustments. |
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