Abstract:

The spatial distribution pattern and sampling technique of the small brown planthopper, Laodelphax striatellus, in paddy field in the Northwestern of Zhejiang province were studied by the methods of the aggregated indices method, Iwao method and Taylor power law method, in order to improve the monitoring, prediction and the sustained control level for this pest in paddy field. All of three methods shown that the distribution pattern of L. striatellus is the assemble distribution type, and the aggregation intensity increased with density of population. It was tested by Blackith’s population aggregation mean number (λ) method, when average population density (m) of adult and adult+nymph was less than 1.3978 and 1.4883 insect/tuft, respectively, their aggregation was caused by some environmental factors, such as surrounding environment, transplanting period, growth period and etc; when m≥1.3978 and 1.4883 insect/tuft, respectively, all λ≥2. The gathering was caused by the interaction of their biological characteristics and environment factor. Based on this distribution pattern, the model for determining the optimum theoretical sampling number and the optimum sequential sampling were proposed. The model were as follows: n=(1.96)2/D2(1.35595/m+0.41366) and T(n)=5n±4.13778 . These results provided scientific basis for sampling investigating precisely and controlling effectively the field populations of L. striatellus.