Pecan growers are thinning it out

By JULIET BRISKIN | Central Texas Edition

August 23, 2001 -- Hedging in pecan orchards has become a hot topic as producers look for ways to generate young wood on over-crowded trees. Recently the Comanche County Extension Commercial Horticulture Committee held a pecan field day that addressed various methods of thinning trees to improve the quality and quantity of pecans.

Hedging, a relatively new technique, was discussed and a tour of a local Comanche pecan producer's orchard allowed participants to see first hand the effects of this thinning method.

"The purpose of this program," said Bob Whitney, Comanche County Extension agent, "is to show growers from this area how to better manage trees that are getting over crowded." According to Whitney the trees that were planted too close together years ago are now posing a severe problem.

Dr. Tommy Thompson, research horticulturist for Texas A&M University, spoke to participants about the effects of hedging on trees, orchard spacing techniques and new pecan varieties that can help enhance existing orchards and create more productive new orchards.

"Today we did a lot of talking about accomplishing one objective," said Thompson, "and that was getting light to the sight of the pecan trees. There is no one answer for this." One important thing to remember said Thompson is that pecans have to have light all the way to the orchard floor.

"If you don't thin out your trees when they get to be 12, 15, 18 years old you are going to have problems," he said. "Your orchard may be a nice place to have a family reunion because everything is shaded, but you are not going to be making a lot of pecans."

According to Thompson, overcrowding of pecan trees will affect both the quality and the quantity of pecans. "Many people feel that you need to have, at the very minimum, 25 percent of the orchard floor with sun on it at high noon," he said. "If you don't have that you need to hedge or thin your trees."

Taking out trees is one option, but many producers have a hard time doing this said Thompson. "It is pretty drastic, but you just have to do it," he said. "It is not as bad as it seems. Yes you are going to take out a lot of your yield the first year, but the remaining trees will compensate for the trees that have been removed."

Another technique Thompson discussed was whisking. "When your orchard gets too crowded, you plan which trees will eventually be removed," he said. "Then you bring the canopy of those trees in, which allows the permanent adjoining trees to move into that area gradually."

After a couple of years of whisking the chosen trees, they will be removed. "This has been done in California walnut orchards for years," said Thompson. "They have had great success with this method and it is not as drastic as going in and removing trees immediately."

Hedging is a relatively new technique where a row of trees is cut similar to a hedge. There are various types of machines that are now being produced that are for the express purpose of hedging but they can be costly. Thompson suggested using a specialized frame that "bolts up under a tractor and has a big sickle attached."

According to Thompson, hedging is time consuming. "If you do it in the wintertime it is a lot cooler," he said, "and it is a slower time of year as far as labor is concerned." After the last crop is harvested and when the temperatures have dropped is when he suggests hedging.

During the tour of Bill Sorrell's orchard outside Comanche, participants were able to see rows of trees that had been hedged and ones that had not. According to Sorrell he cut his trees about eight feet from the center on both sides creating a 16-foot wide hedge.

Through trial and error Sorrell has learned the best way to make the hedge cuts. "If you cut at an angle the limbs just slide down," he said. "If you cut flat the limbs will dump right back on to the tree and the saw does not operate as well."

After the tour Bill Ree, Extension entomologist, discussed pecan weevil prevention. "Our whole program for the pecan weevil," he said, "is aimed at preventing the female from laying eggs in the pecan." According to Ree, weevils do not spread very much. "Most movement of the weevil is man assisted," he stated.

The pecan weevil spends two to three years in the soil. "We can't do anything about the weevils in the soil," said Ree. "The only opportunity we have to manage weevils is when the adults emerge from the soil and before they lay their eggs."

"In managing weevils we have to consider three things," Ree stated. "The first is kernel development, second is monitoring adult weevils and the third is using effective insecticides." The weevils come out of the ground around the first of August and the first treatment with insecticide should be done around August 20 to 22, according to Ree.

"Along with that date I would be out cutting off some pecans and looking at how my kernel development is coming along," he stated. "When you are checking for kernel development you need to look toward the tip end of the nut. The nut matures from the tip back and the female weevil knows that. Her early egg laying will be at that tip end."

When monitoring adult emergence Ree feels that using some type of trap is the best method. There are numerous types of traps available and according to Ree they all have advantages and disadvantages.