Development and Validation of Prediction Equations for Estimation and Control of Pecan Weevil 1 Populations 2

Abstract

Data collected in 1972, 1973, and 1974 were used to develop equations for estimating pecan weevil, Curculio caryae (Horn), populations from trap catch at 2-day intervals. Two of these equations were modified by adding a survival factor, validated under field conditions for estimating the number of pecan weevils in a tree, and for timing insecticide applications. Timing of insecticide applications based upon a threshold of 40 weevils/tree as estimated by the prediction equation resulted in 2.4, 0.6, and 0.4% of the nuts with grubs in 1974, 1975, and 1976, respectively. The high number (>350 collected in traps under a tree with a history of a high infestation) of weevils emerging under pecan trees in 1974 and low numbers (<40 collected in traps under the same tree) in 1976 was a further check on the accuracy of the evaluation of weevil damage (nuts with grubs) and control in 1974. The pecan weevil has predominately a 2-yr life cycle and grubs entering the soil in 1974 emerged as adults in 1976. Also, a method is provided which allows practicing entomologists or pecan growers to readily predict number of pecan weevils in a tree from trap catch.