LSU AgCenter Entomologist Warns About Pecan Phylloxera

Linda Benedict  |  4/22/2005 8:45:00 PM

News Release Distributed 04/08/05

SHREVEPORT – As Louisiana enters the pecan-growing season, LSU AgCenter specialists warn growers to be on the lookout for a dot-sized insect known as the phylloxera.

Dr. Michael Hall, an entomologist at the LSU AgCenter’s Pecan Research and Extension Station near Shreveport, said he has noticed bud breaks occurring on some of the earlier maturing pecan cultivars.

"This means the emergence of pecan phylloxera will soon be, if not already, occurring," Hall said.

The pecan phylloxera is an aphid-like insect that leaves galls, or knots, on leaf veins, leaf rachises, stems and nuts of pecans. The insects overwinter as eggs in the body of a dead female phylloxera. The eggs hatch in the spring, about the time the buds are beginning to open, Hall said.

"In Northwest Louisiana, the phylloxera hatch from mid- to late March," Hall said. "Once they hatch, the phylloxera move to the newly open buds and begin feeding.

"As an insect feeds, a gall begins to form around the insect, eventually enclosing it. It is only this generation that forms galls and causes the damage."

There is no treatment threshold for this insect, Hall said. Control measures, if necessary, should be initiated about the time the buds show a half-inch to three-quarters of an inch of new growth.

"Treatment applications should be made prior to gall formation, because control measures are no longer effective once the phylloxera are in the gall," Hall said.

Peak pecan phylloxera emergence usually occurs between April 6 and April 10, Hall said. Weather changes, primarily temperature changes, can cause these dates to vary slightly. Hall advises growers to begin scouting for phylloxera at the onset of bud break.

"Use a 10X or higher hand lens or magnifying glass to inspect buds for the presence of pecan phylloxera," he said.

The pecan phylloxera is a small insect that is yellowish-orange, with dark gray legs.

If phylloxera are detected, Hall suggests using insecticides such as Lorsban 4E at 1.5 pints to 2 pints per acre or Provado 1.6F at 4 ounches an acre. Other insecticides labeled for use against the pest include Warrior at 3 ounces an acre and Mustang Max at 3 ounces an acre.

Hall cautions not to spray, however, if phylloxera are not detected.

For questions about pecan phylloxera, contact Hall at (318) 797-8034 ext. 2320, or e-mail him at mhall@agcenter.lsu.edu.

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Writer: A. Denise Coolman at (318) 633-5865 or dcoolman@agcenter.lsu.edu

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