Spatial distribution of Scythropus yasumatsui adults and sampling techniques for this species in the Jujube growing region of Northern Shaanxi
Author of the article:YAN Xiong-Fei** PU Tai-Xun LI Gang LIU Yong-Hua
Author's Workplace：College of Life and Science
Key Words：Scythropus yasumatsui; adult; spatial distribution pattern; sampling technique
Abstract： [Objectives] Scythropus yasumatsui Kono et Morimoto is one of the most important pests of jujube trees. In recent years, S. yasunatsui irruptions in the jujube growing region along the banks of the Yellow River in North Shaanxi have caused enormous economic losses to the jujube industry of this region. The aim of this research is to determine the spatial distribution pattern of S. yasumatsui adults in the region, and develop effective sampling techniques for this species, thereby providing a theoretical basis for more accurate monitoring, prediction and control of this pest. [Methods] We selected 5 representative jujube fields as sampling sites in Jia County in 2015, and evaluated five different sampling methods (five-point sampling, double diagonal sampling, chessboard sampling, parallel sampling lines and Z-shaped sampling). The number of adult weevils on each jujube tree was recorded using stratified sampling. The suitability, representativeness and variability of the five sampling methods were compared and analyzed using t-tests. The spatial distribution pattern of S. yasumatsui adults in the jujube region was studied using aggregation indices, Iwao’s m* - m regression analysis method and Taylor's power law. The theoretical sampling number and a sequential sampling model for adult weevils was determined using Iwao's theoretical sampling and sequential sampling formulae. [Results] All five sampling methods were effective but the parallel sampling method was the best. S. yasumatsui adults have an aggregated spatial distribution in the jujube growing region of Northern Shaanxi. The basic component of the distribution was a group of individuals; individuals attract each other so the greater the density the higher the degree of aggregation. The reason for this aggregation is either some environmental factors or an innate tendency of this weevil to aggregate. The optimum theoretical sampling model was N=t2/D2 (18.995/m+0.020 3) and the optimum sequential sampling model was . [Conclusion] The parallel line sampling method was the best for investigating the spatial distribution of S. yasumatsui adults，which was found to be aggregated. These results provide basic data for monitoring, predicting, and the effective and sustainable control of S. yasumatsui in the jujube growing region of Northern Shaanxi.