08/26/1993

Midsummer Crop Thinning May Save Overloaded Pecan Trees

FAIRHOPE, Ala. - While most pecan growers are trying to figure out how to get more nuts on their trees, Auburn University researchers are trying to figure out how to get more nuts off trees at the Gulf Coast Substation here.

The concept of thinning a crop to get maximum production from the fruit left on the tree is not new to fruit producers--in fact it is routine. But to most pecan growers thinning is not only not routine, it's down right ridiculous. As one long time Baldwin County grower put it, "I thought I'd seen it all, but shaking green pecans in August takes the cake."

In tests by the Alabama Agricultural Experiment Station, seven varieties of pecans at the Gulf Coast Substation were thinned using a specially designed shaker. The trees originally had 90-95 percent of the terminals with nuts, an excessive crop load. The trees were shaken until either 20 percent, 50 percent or 70 percent of the terminals had nuts remaining. The green pecans, which were in the water stage of development, were weighed, and as many as 168 lbs. of nuts were removed from the heavily-loaded 11-year-old trees.

The theory behind thinning pecans at the water stage is to increase the quality of the remaining nuts. Thinning also leaves the tree in better condition to produce a heavier load of nuts the following year, which could offset the historic problem of alternate season bearing in pecans. In tests in Oklahoma, quality has been improved both years and total yield on thinned versus unthinned trees has been about the same.

"We won't know how successful we are in the long run for a couple of years, because we will have to wait and see how the trees that we thinned this August produce next year," noted Auburn researcher Bill Goff. For sure, this is a good year to put thinning to the test, because trees statewide are loaded with pecans, Goff concluded.

"In some varieties here at the Station, we have lost significant amounts of wood because of limbs being loaded down with pecans. So, we are seeing an immediate reduction in limb splitting in the trees we thinned. With such a heavy crop on some of these varieties, a thunderstorm, much less a hurricane, would have really torn them up," noted Ronnie McDaniel, associate superintendent of the Gulf Coast Substation.

McDaniel pointed out that improved shakers and careful attention by growers can allow thinning at the water stage without damaging trees. The bark of pecans is highly susceptible to damage at this stage, but McDaniel pointed out that researchers shook about 80 trees with no apparent damage.

This research and projects on weed control, pest management and irrigation management will be shown to visitors attending the Annual Alabama Pecan Growers meeting, which will be held at the Gulf Coast Substation Sept. 16-17.

"You can look at the trees we shook, and see that the limbs have straightened up. On trees we didn't shake, we continue to have prune out broken limbs. We don't know how many pecans we lost on broken limbs, but it would be signficant, and 20-30-foot limbs don't grow back over night," McDaniel concluded.

Whether pecan thinning will become as common as peach or apple pruning remains to be seen. "This test won't give us all the answers, but it will give us some valuable information. If thinning helps offset alternate season bearing and keeps quality uniform over a long period of time, then these results will be valuable in deed," Goff concluded.

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News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
by Roy Roberson

August 26, 1993