Picking Off Pecan Weevils
October 25, 2000
Agricultural Research Service entomologists
are helping pecan farmers devise new strategies to control crop-damaging pecan
weevils (Curculio caryae), pests that cost growers $14 million annually
Older pecan trees have alternate years of heavy and light crops, called
alternate bearing. Pecan weevils are attuned to trees production peaks.
They burrow into soil surrounding trees and emerge to reproduce during the year
when trees are most productive, every two years.
Researchers at ARS
Fruit and Tree Nut Research Laboratory in Byron, Ga., are studying weevil
emergence behaviors to determine how many pests fly into tree canopies and
crawl up tree trunks.
To control weevils, growers typically treat the canopy with pesticides,
killing beneficial insects that would feed on other pecan pests such as aphids
and mites. ARS researchers found that many adult weevils crawl to the trunk
after emerging from the ground. If researchers can determine what percentage of
weevils fly versus crawl onto trees, growers can use this information to treat
specific tree portions, cutting down on pesticide use, which is good news for
ARS researchers are also working with University of Georgia scientists on developing a
naturally occurring fungus, Beauveria bassiana, as a promising weevil
control. In a preliminary field study applying a fungal moat around
a tree, the fungus killed 90 percent of weevils during the first two days. The
researchers will study changes in the fungus effectiveness and
persistence over time.
Another promising weevil control study just starting at Byron focuses on
microscopic, insect-killing worms called nematodes. The researchers will
evaluate which out of 30 species of insect-killing nematodes is best at
controlling pecan weevils.
ARS is the U.S. Department of
Agricultures chief research agency.
Scientific contact: Ted E. Cottrell and David Shapiro, ARS
Southeastern Fruit and Tree Nut Research Laboratory, Byron, Ga., phone (912)
956-6421, fax (912) 956-2929, email@example.com,