Intraplant Distribution of Immature Lifestages of Bemisia argentifolii (Homoptera: Aleyrodidae) on Tomato

Abstract

The intraplant distributions of eggs, sessile nymphs, and pupae (red-eye nymphs) of the whitefly Bemisia argentifolii Bellows & Perring [formerly referred to as strain B of the sweetpotato whitefly, B. tabaci (Gennadius)] were studied on the terminal 3 leaflets of leaves on main and lateral stems of tomato, Lycopersicon esculentum Miller, in field plots. The distributions of specific lifestages depended on the age of leaves. Eggs were most abundant and variation generally low or lowest on leaflets at nodes 4-6 (counting from the terminal), nymphs at nodes 6-8, and pupae at nodes 8-10. The nodal position of the most infested leaf tended to increase within the above ranges as the season progressed. The distribution of immature lifestages on leaflets at different nodes was independent of stem origination as long as the number of nodes present were similar on main and lateral stems. The b dispersion index from the Taylor power law for each lifestage did not vary significantly over nodes and over main and lateral stems within the above ranges of nodes for each lifestage. Single lna and b values were calculated for each lifestage and were used to estimate minimum sample sizes (a sample unit consisted of the terminal 3 leaflets from the above respective nodes for each lifestage on either a main or lateral stem of 1 plant). Estimated minimum sample sizes at a precision of 0.25 (SEM/mean) increased with increasing density of eggs but decreased with increasing density of nymphs and pupae. The minimum sample size did not exceed 13, 23, and 28 for eggs, nymphs, and pupae, respectively, at a density as low as 1 immature per sample.