Population Fluctuation and Spatial Distribution of Thrips in Bean Farms (Phaseolus Vulgaris L.) in Lorestan Province, West of Iran

Considering the significant damage caused by thrips species to the bean crops, population fluctuation, species diversity, and spatial distribution thrips’ relationship to the growth stages of red bean (Phaseolus vulgaris L.) was investigated in the bean farms of Selseleh county (Lorestan province, west of Iran). Sampling was done at the same time as the bean became two leaves until the leaves dried in two farms located in the villages of Cham-Takleh and Dartang during the year 2021. The sampling was done in the farms by moving in a W-shape. In each sampling, 20 leaves were selected and then the thrips were collected by shaking the leaves on a white tray. In this study, 12 species of thrips were collected and identified. Amongst them, the highest frequency was related to onion thrips, Thrips tabaci Lindeman (69.43%). The results of population fluctuation showed that in Cham-Takleh, the highest density of onion thrips and flower thrips was 166.35 ± 4.99 and 16.85 ± 1.38, respectively, and in Dartang, the highest density was 159.3 ± 3.61 and 22.6 ± 1.32 on average. Also, in both locations, the highest values of biodiversity indices were observed in the reproductive stage of the bean. The highest values of Shannon-Wiener, Simpson, Pielou evenness, and Margalef richness indices in Cham-Takleh were 2.94, 0.93, 0.95, and 2.98, and in Dartang were 2.89, 0.91, 0.94, and 2.74, respectively. In general, the results of this study showed that the population peak of onion and flower thrips was observed in the reproductive and development of pod stages of beans, and their density gradually decreased in the farms. Considering that at this stage of the bean, thrips can cause a lot of damage to the bean crops, so appropriate management measures can be provided for the farmers.