Biological Control of Pecan Weevils in the Southeast

Pecan (Carya illinoensis) is the most valuable nut crop native to North America. There are more than 492,000 acres of managed pecans in the United States, with major production in the Southeast, Southwest and parts of the Midwest. Total annual value of the crop to U.S. growers generally exceeds $300 million.

Insects and mites can cause severe crop losses in pecans. Of major concern is the pecan weevil, Curculio caryae (Fig. 1). This weevil attacks the pecan nut in late season, causing serious crop losses in many areas of the Southeast, Texas and Oklahoma. It is considered a key pecan pest, as damaging populations occur year after year. Without insecticide treatments, crop losses can exceed 75 percent.

Our research goal was to provide an alternative control strategy for pecan growers who, for a variety of reasons, find conventional spraying of insecticides unsuitable. This includes organic growers, and owners of dooryard trees, small orchards and commercial orchards who have concerns regarding spray drift. We attempted to sort and identify naturally occurring fungal strains that were effective at killing pecan weevils and provided improved fungal persistence in the orchard, thus extending the effective period of control. We also sought to develop an efficient and practical method of applying the fungal formulations in pecan orchards. This fact sheet provides information about the life cycle of the pecan weevil and its impacts on pecan crops; identifies fungal pathogens that can control pecan weevils; and outlines methods for application of these fungal pathogens in orchards.

Geographic adaptability: The techniques discussed here are applicable to pecans grown in areas of the southeastern United States where pecan weevil is a key pest.

Want more information? See the related SARE grant(s) LS03-153, Integrating Biological Control into Pecan Weevil Management: A Sustainable Approach.