Document Type : Agricultural Entomology
Authors
Abstract
The whiteflies, Bemisia tabaci Gen. and Bemisia argentifolii Bellows & Perring and the leafhopper Empoasca decipiens Paoli are the most serious and polyphagous pests on wide rang of economic crops in Iran and other places especially in tropical regions. Both of the whiteflies in adult stage are too similar to identify them particularly in field conditions, so population fluctuation and spatial distribution of whiteflies as mixed of two species B. tabaci and B. argentifolii with E. decipiens was studied on eggplant crops in Varamin region weekly during 2006. The k parameter, index of dispersion, Lloyd’s mean crowding, Morisita’s index and regression methods (Taylor and Iwao) were used to estimate the spatial distribution pattern of insects. There was improved sampling program by k parameter and coefficients of regression models. Whiteflies were seen one week later than leafhopper in middle of May. The result indicated that the highest population density of B. tabaci + B. argentifolii and E. decipiens was early of June (4.89 per leaf) and early of August (6.69 per leaf). Both of populations were reached to zero in early of October. All of used methods except index of dispersion of whiteflies were shown an aggregated distribution for all species, but index of dispersion for whiteflies was determined random behavior. The reliable sample size (number of leaves) with maximum variance of 20% was about 38 and 20 leaf for whiteflies and leafhopper, respectively. Sampling program was improved by k parameter, 103.37 and 155.42, coefficients of Taylor 14.98 and 0.88 and Iwao’s coefficients 149.39 and 63.35 sample units for whiteflies and leafhopper, respectively. The difference between sample sizes may be due to different precision of indexes. Determining sampling program and spatial distribution pattern of the pest can effectively help to design and perform of IPM.
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