Study On The Important Natural Enemies Eucryptorrhynchus Brandti (Harold) Of Invasive Plant Ailanthus Altissima (Mill.) Swingle In Northern American

Ailanthus altissima (Mill.) Swingle was an invasive plant in the United States, for it is capable of prolific roots and stump sprouting as well as producing a generous amount of seed. If allowed to establish itself, A. altissima will create a pure stand, with little opportunity for other plant species. A. altissima has also been found to produce allelopathic compounds in its bark and leaflets that are toxic to numerous woody and herbaceous species. Eucryptorrhynchus brandti (Harold), which mainly fed on A. altissima, was a forestry pest in China and was considered to be a potential natural enemies of A.altissima. Both field and laboratory surveys were carried out to observe the biology of E. brandti, combined with related materials, the potential distribution of E.brandti in the United States were predicted using CLIMEX. Futhermore, the host specificity of E. brandti were also tested.1. E. brandti, which occurred one generation in Ninxia, Gansu, Anhui and Shandong, respectively, has been known to distribute in 15 provinces,municipalities and autonomous regions. E. brandti overwintered by adult and larvae. E.brandti mainly fed on A. altissima with circumference longer than 60 cm.2. Influence of constant temperatures (20℃, 24℃, 28℃, 32℃, and 36℃) on the development and survival rate of E.brandti were also studied. The result showed that the developmental durations was shortest , but the survival rate was highest at 32℃. The development initial temperature calculated by linear regression model and Logistic model were 3.1324℃,6.7194℃,respectively,and effective accumulative temperature calculated by two methods were 6.7194℃and 1352.8 degree-day, respectively. The SCP(supercooling point) determined at pre-winter, mid-winter and post-winter were -13.16℃,-15.30℃and -5.23℃, respectively. Female adult's SCP of Shandong, Liaoning and Shanxi population which determined in July were -7.80℃,-6.86℃and -9.83℃, respectively, while male's SCP were -8.12℃, -9.76℃and -10.48℃, respectively. High temperature influenced the development of egg and naive larvae. After treated 72h at 50℃, egg mortality reached 55% and larvae morality reached 100%. Low temperature greatly influenced morality of eggs and larvae, after treated 12h at -14℃, egg morality reached 100% and egg morality reached 100% after 6h. at -20℃After treated 48h at -14℃, larva morality was 95%, while treated 48h at -20℃, morality reached 100%. Adult weevils could resist low temperature, highest morality was 20% above -15℃, but below -17℃, adult morality reached 100% after 6h.3. 35 plant species from 24 families were used to test host specificity of E. brandti. Non-choice experiment showed that adult weevils fed on 7 species from 5 families, larvae fed on 10 species from 8 families. Choice experiment showed that adult fed on 4 species from 2 families. But E. brandti could only complete whole generations in A. altissima.4."Compare location"method of CLIMEX was used to predict the potential distribution of A. altissima in the United States. Result demonstrated that 58 locations of 20 states, most of which were located in middle and western America, were suitable for the development of E. brandti, but potential distribution of E.brandti in the United States was smaller than actual distribution of A.altissima in the United States.