Damage Characteristics And Spatial Distribution Of Three Species Of Insect Pests On Salix Psammophila

Salix psammophila is main tree for windbreak and sand fixation in northwest of China, which has been seriously harmed by 3 pests (Leucoma salicis, Holcocerus arenicola and Oberea oculata) in recent years. In order to understand damage characteristics, spatial distribution and relationship of three pests in S. psammophila were analyzed by using biostatistics and geostatistics method. Main conclusions are as follows:① Spatial characteristics of L. salicis larvae and pupae in S. psammophila woodlands:The results indicated that the population quantity of L. salicis larvae and pupae reached the maximum at top of the dune with 17.03±5.15 head/crowd and 15.24±5.26 head/crowd respectively, which had no significant difference comparing with the quantity distribution at bottom of the dune. The quantity of L. salicis larvae and pupae in perennial S. psammophila woodlands were the largest with the number of 20.31±2.39 head/crowd and 18.02±3.19 head/crowd respectively, which differed from those in biennial woodlands significantly. Geostatistical analysis showed that L. salicis larvae and pupae distributed as aggregated stripe in the sample plots of perennial woodlands at top of the dune, and biennial woodlands both at top and at bottom of the dune. The aggregated plaques decreased slightly from the aggregation center to edges. The L. salicis larvae and pupae in the sample plots of perennial woodlands at bottom of the dune distributed randomly. The spatial distribution patterns of the larvae and pupae were similar in different sample plots.② Damage characteristics and spatial distribution of H. arenicola larvae population on S. psammophila. The results of biostatistics analysis showed that the larvae of H. arenicola distributed on the roots,91.2% of total S. psammophila samples were found to be damaged by more than 5 heads/crowd; and different age groups of pests can harm the same plant at the same time.78.57% of the larvae population was concentrated in the roots within 10-40 cm underground; the population density of H. arenicola larvae related to diameter size and distribution of the root. The results of geostatistical analysis showed that H. arenicola larvae followed an aggregation distribution, and aggregation points were distributed in the northeast and southwest area of the sample plot and then spread to other areas.③ Damage characteristics and spatial distribution of O. oculata on S. psammophila. O. oculata larvae focused on base of S. psammophila in a single tunnel, the tunnel extended 10-15 cm on the ground and 5-8 cm underground. S. psammophila with 0.7-1.0 cm diameter were mainly damaged, which distributed at bottom and at top of the dune.Analyzing O. oculata larvae quantity at two woodlands, the damage percentage of S. psammophila at the bottom of the dune are higher than at the top of the dune, the larvae number were 2.53 ± 0.27 and 2.53 ± 0.20 head/crowd at the two woodlands, which was a significant difference. O. oculata larvae spatial distribution at bottom of the dune were aggragated, under different site conditions, the difference of spatial distribution in two woodlands is obvious, but the aggregation points were in a particular area in the two woodlands.④ Comparative analysis on damage characteristic and spatial distribution of three species of insect pests:Three species of insect pests damaged S. psammophila woodlands with larvae. Regardless of different areas within the same year, or in the same area at different years, three species of insect pests have gathered in a specific area. Combining spatial distribution map, analyze three species of insect pests in the three plots:Positive correlation between L. salicis larvae damage and H. arenicola larvae damage; negative correlation between L. salicis larvae damage and O. oculata larvae damage, and H. arenicola and O. oculata showed a negative correlation.