Biological Control Of Asian Longhorned Beetle With Great Spotted Woodpecker In Agroforestry System

Poplar longhorned beetles(PLB),with particular respect to Asian longhorned beetle Anoplophora glabripennis,are one of the most important groups of pest insects in the northern provinces of China.In these provinces the increase in PLB population density during the past three decades provided abundance of food supply for insectivorous birds,like woodpeckers,and caused the population increase of Great Spotted Woodpecker Picoides major since the beginning of 1990's.In plast years,reduction of PLB population was observed as a consequence of the higher feeding activity of P.major.In the present PhD dissertation,the biology and feeding ecology of P.major were investigated,as well as the control effect of P.major against A.glabripennis population.Moreover,an attraction technique using artificial nest-woods was established based on our experimental investigations of nest and habitat analysis of P. major in the agroforestry ecosystem of Wulateqianqi,Inner Mongolia from July 2004 to June of 2008. The main results achieved during this period were the following:1.In the selected areas the breeding time of P.major was found to start from the beginning of April and to end in the middle of June.Females usually produced 4-7 eggs per one clutch,laying one egg per day.The duration of the incubation period was estimated around 13 days with about 51.2%eggs being hatched successfully.The nestling period was about 25 days before the young woodpecker flied away from the nest-cavity for the first time and the rate of breeding success was around 88.24%.2.Foraging and pecking were the main behaviours of P.major observed during our investigations. Behavioural rhythm was clearly present in summer with a rest peak at midday,but a rhythm in behaviour was not recorded in winter.The time spent by the birds for movement was much longer in summer than in winter and significant differences were observed of behavioural patterns in different seasons.However,there was no detectable difference in behaviour between the two sexes.3.Over the course of this study,foraging observations were recorded.The foraging times per day were 49.75±8.73,57.75±8.68,and 37.62±6.07 in spring,summer and winter respectively.The times per day when P.major pecked up A.glabripennis larvae during the three reported seasons were 1.58±0.27, 1.26±0.19 and 11.91±1.92,respectively.We found a significantly higher foraging on A.glabripennis larvae during the winter season compared to the other seasons(ANOVA:F=16.4010,df=2,P=0.0001). Therefore,winter was considered to be the crucial time to control A.glabripennis with P.major.The total annual rate of pecked A.glabripennis larvae by P.major was 30.72±29.06 and the rate of successful pecking was 88.33±25.00,not considering the impacting factors like different seasons and the age of A.glabripennis larvae,etc.However,the rate of pecked A.glabripennis larvae and rate of successful pecking were found to vary greatly during the different seasons,being 42.76±35.98,17.15±25.92 and 32.87±18.35 for rate of pecked larvae,and 89.76±18.43,74.00±42.53 and 94.94±11.10 for rate of successful pecking in spring,summer and winter respectively.The rate of successful pecking on young A.glabripennis larvae was much higher than that on old ones,but no detectable difference was observed between the rate of pecked larvae in different ages,that means no selection in the age of A. glabripennis larvae for P.major.The pecking times on branches was found to be more than on trunks, therefore we concluded that P.major prefers to forage from crown parts than from trunk parts of tree.In addition,P.major spent more time foraging on dead parts than on living parts of trees.According to these results,and to improve the effect of PLB population control,we decided to move away the dead trees and dead branches in order to push P.major foraging A.glabripennis larvae from the living parts of poplar trees.4.The foraging function of P.major on the larval population of A.glabripennis was modelled, considering the population density of A.glabripennis and the rate of damaged trees.Different models were developed for each season.In winter and spring,the foraging rate of P.major was negatively related with the population density of A.glabripennis and with the rate of damaged trees,but positively related in summer.Autumn was not taken into consideration,due to the lack of sufficient investigations during this period.Comparing the investigated areas with control areas,where P.major was not present, we found that A.glabripennis population increased relatively slower of 42.05%due to the predation of P.major.The territory occupied by one breeding pair of P.major varies in function of the different population density of A.glabripennis,being 86.32±58.34 ha in slightly infested areas,53.51±12.99 ha in moderate infested areas and 30.52±6.84 ha in heavily infested areas..Measurements like moving away the severely damaged trees was estimated to be able to improve the control effect against A. glabripennis with P.major in long term.5.Two nest-excavation peaks for P.major per year were observed.The first one occurred during late autumn-early winter and the second one occurred during the breeding time in spring.The average number of newly produced nests for one pair of P.major was 5.40±1.97 per year.The main affecting factors on the selection of nest sites were the age,height and rotten degree of tree and the concealment and protuberance for rain prevention of selected site.The orientation of nest-cavity entrance was found to be mainly directed to the north,north-east and east.The main affecting factors on the selection of habitats were the rate of dead trees,size of patch forest,age,height and diameter of tree and availability of food resource.The average area of habitat for one pair of P.major was estimated 72.53±38.01 ha, varying from 27.02 to 150.45 ha.Based on these findings we propose that attraction with artificial nest-wood on P.major should be carried out in agroforests,where there were full shelter belts and P.major living.However,there should not be a high proportion of dead trees because P.major might prefer the natural nest-woods than the artificial ones.Artificial nest-woods should be hanged each year and the optimal hanging time was from end of February to beginning of March.The proper number of nest-wood was estimated to be 8 for one pair of P.major.Nest-woods should be rotten inside with the presence of clear protuberances and with a diameter larger than 20 cm.In our experiences,it is better to hang the nest-woods as high as possible, but practically the optimal height is around 3.5 m being really labour-costing to hang the nest-woods higher than 4.0 m.Nest-woods should be arranged in one line along the shelter belts with distance of 100 m between each other or in two paralleled lines.Nest-woods should be hanged on the host trees with the direction oriented to north,north-east or east.Moreover,the nest-woods should be hanged in the central part of an agroforest area to avoid disturbance and destruction.