INTRAPLANT DISTRIBUTION OF IMMATURE LIFESTAGES OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) ON TOMATO

The intraplant distributions of eggs, sessile nymphs, and pupae (red-e ye nymphs) of the whitefly Bemisia argentifolii Bellows & Perring [for merly 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 node s 6-8, and pupae at nodes 8-10. The nodal position of the most infeste d leaf tended to increase within the above ranges as the season progre ssed. The distribution of immature lifestages on leaflets at different nodes was independent of stem origination as long as the number of no des present were similar on main and lateral stems. The b dispersion I ndex from the Taylor power law for each lifestage did not vary signifi cantly over nodes and over main and lateral stems within the above ran ges of nodes for each lifestage. Single Ina and b values were calculat ed for each lifestage and were used to estimate minimum sample sizes ( a sample unit consisted of the terminal 3 leaflets from the above resp ective 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/mea n) increased with increasing density, of eggs but decreased with incre asing density of nymphs and pupae. The minimum sample size did not exc eed 13, 23, and 28 for eggs, nymphs, and pupae, respectively, at a den sity as low as 1 immature per sample.