بررسی تغییرات جمعیت و الگوی توزیع فضایی سنک گلابیStephanitis pyri (F.) روی درختان گلابی در استان لرستان

The pear lace bug, Stephanytis pyri (F.) (Hemiptera: Tingidae) is one of the main pests of pear trees in different regions of Iran. Lace bug damage is not usually economic, but serious invasions can cause considerable damage or even death to the host. In the present study, the pest population fluctuations and spatial distribution were investigated in pear orchards of Khorramabad (Lorestan province), during 2019-2020. Sampling was carried out once every 14 days from April to November in both years. In each sampling date, 70 leaves were randomly collected from the trees and the number of lace bugs was counted under a stereomicroscope. To estimate the spatial distribution pattern, data were analyzed through the Index of dispersion, Lloyd's mean crowding, Green index, Morisita's index, and two regression models (Taylor’s and Iwao’s). The pear lace bug overwintered as an adult within weeds until late May; after that, they migrated to the pear trees and distributed on the leaves. As a result, there was a positive and significant correlation between population density and temperature in both years. Moreover, the highest population density of the pest was observed in August and July (in 2018 and 2019, respectively). The spatial distribution pattern of pests using non-regression methods was aggregated and by using Taylor and Iwao regression methods in 2019, the pattern of insect distribution was determined as random and in 2020 as cumulative. The results of this study can be used to determine the required number of samples and management programs for this pest.