Louisiana Pecans: Diseases, Insects Featured at Grower Meeting

By Rick Bogren, LSU AgCenter

Choosing the proper fungicide and alternating among those in different chemical groups are important considerations in managing diseases in pecan trees, experts told the audience at the Tri-State Pecan Growers Convention on June 17.

About 160 pecan producers and other industry representatives attended the convention, said Stephen Norman, president of the Louisiana Pecan Growers Association, which hosted the meeting.

The convention serves growers in Louisiana, Arkansas, and Mississippi, Norman said.

“Several diseases have the potential to infect pecans,” said LSU AgCenter plant pathologist Randy Sanderlin.

Scab disease is the most common, Sanderlin said, followed by anthracnose, neofusicoccum, sooty mold as a result of honeydew from yellow aphids, and bacterial leaf scorch, which could be confused with the effects of pecan scorch mites.

“Even when there is no crop on the trees, growers should apply fungicides to protect leaves from pathogen infection at least through mid-June,” he said.

“After mid-June, the use of fungicides when there is no crop on the trees may not provide much value in the current year,” Sanderlin said. “However, the condition of the foliage this year will affect crop production for a least the next three years.”

It’s important to know the different fungicides, said Katherine Stevenson, a plant pathologist with the University of Georgia.

For scab disease in particular, alternating fungicides with different modes of action is important to avoid creating fungicide resistance in the pathogen, she said.

“Select the frequency and timing of applications, and know management options,” Stevenson said.

When it comes to controlling insects, having the proper pH in mix water is important to the success of insecticides, said AgCenter entomologist Dennis Ring.

Ring presented several examples of how the effective control of various insecticides is reduced by mixing them in water with the wrong pH.

Water pH can be changed by adding a buffer, but “add buffers little by little to reach the optimum pH in the spray water,” he said.

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The primary concern with insects is those that feed on nuts, and a secondary concern is those that feed on leaves. “We need leaves on trees as long as we can into December to make food for next year,” he said.

“Identify the problem and know how many insects are present, when to treat and the treatment required,” Ring said.

Pecan weevil is the most-damaging late-season pest. Use cages to collect and measure weevil populations, he said.

AgCenter pecan specialist Charlie Graham talked about the new FDA Food Safety Modernization Act and how it may relate to pecan growers.

Because pecans are rarely consumed raw by a majority of Americans, the crop is exempt from the regulations. “This is something we have to monitor over the next several years,” Graham said.


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