Spatial distribution of greenhouse whitefly (Trialeurodes vaporariorum Westwood) and a suggested sampling plan for estimating its density in greenhouses

Spatial distribution of the greenhouse whitefly population infesting tomato plants in greenhouses was analyzed. A leaf of tomato consists of 7 leaflets, each being used as a basic sampling unit. Distribution patterns between plants, between leaves and between leaflets were analyzed by the analysis of variance and the method. It was found that populations of all the developmental stages were composed of contagiously distributed colonies or individuals between leaves and between leaflets. On the other hand, they showed random distribution of colonies between plants. On leaflets, egg populations were distributed as colonies, each consisting of several eggs, while in larval and adult populations, individuals were distributed rather independently of each other. A three-stage sampling plan was developed to estimate the density at the assigned level of precision.