COMPARATIVE-ANALYSIS OF SELECTED SAMPLING METHODS FOR ADULT BEMISIA-TABACI (HOMOPTERA, ALEYRODIDAE) IN COTTON

We evaluated the reliability anti efficiency of various sticky traps a nd 2 direct-count sampling methods for estimating tbe abundance of Bem isia tabaci (Gennadius) adults in cotton, Gossypium hirsutum L., durin g a 3-yr period. Comparing sticky traps of various sizes, orientations , and placements, horizontally oriented traps (7.6 by 7.6 cm) with the upper surface exposed consistently captured the most adults per squar e centimeter over the season when placed at ground level at field edge s followed by those placed within fields at ground level. Before insec ticide applications, captures on all trap types and counts using a lea f-turn method and an oiled black pan method were highly correlated wit h the abundance of immatures in the field the same week, and even bett er col related with immatures counted 1 wk later. After insecticide ap plication, correlations were Lower and more variable. Regression equat ions relating adult abundance to immature populations varied significa ntly between sites and over years for all adult sampling methods. This , robust predictive relationships could not be formulated. The 2 direc t-count methods were highly correlated with one another, but the leaf- turn method was much less variable between individual samplers than th e black pan method when estimating populations in the same field. Acco unting for sample sizes needed for an acceptable level of precision an d the per unit cost (time) of each sampling method, the black pan meth od was 3.5 times more costly than the leaf-turn method, and sticky tra ps were from 3.6 to 19.7 times more costly in estimating populations i n the same fields. on average it took approximate to 6 min to estimate adult populations with a precision (SE/mean) of 0.25 using the leaf-t urn method. Based on between-sampler variability, and cost considerati ons, the leaf-turn method was the most reliable and efficient techniqu e for estimating adult abundance of those examined.