Standardised sampling plan for Bemisia tabaci (Homoptera: Aleyrodidae) in outdoor tomatoes

The objective of this work was to determine a standardised sampling plan for Bemisia tabaci Genn. (Homoptera: Aleyrodidae) in outdoor tomatoes. Eight commercial crops of tomato in the Municipalities of Coimbra and Viçosa, Minas Gerais State, Brazil were used to assess the density of nymphs and adults of B. tabaci on tomato leaves. Twelve sampling methods were compared. Each consisted of one of two sampling techniques (beating tomato leaves in plastic trays and direct counting of insects on leaf surfaces), one of three sizes of sampling units (one, two and three leaves) in either the apical and basal parts of the canopy of tomato plants. The most appropriate sampling methods were beating one apical leaf in the tray to assess adults and by direct counting of nymphs on a basal leaf of tomato plants. The number of samples, when estimating the population density with a specified precision level equal to 20%, was 45 samples/plantation for nymphs (Kcommon = 0.737) and 24 samples/plantation for adults of B. tabaci (Kcommon = 1.10).