Mechanical thinning of pecans provides financial benefits

Monte Nesbitt, Bill Goff, Ron McDaniel, Malcomb Pegues

             Crop thinning has been proven to have two effects on pecan trees; improving kernel grade and reducing the severity of biennial or “alternate” bearing (nut crops every other year).  The practice of reducing crop load with mechanical trunk shakers was introduced in the state of Alabama in 1993 through a study of differential levels of thinning on several pecan cultivars at the Gulf Coast Regional Research and Extension Center in Fairhope, AL.  Results from the Fairhope experiment showed that pecan cultivars respond differently to thinning. 

Some pecan cultivars, like ‘Cape Fear’, produce poorly developed kernels when the crop is big, and shaking some nuts off the tree in late July will improve the overall kernel percentage and the dollar value of the crop.  If the dollar value improvement is great enough to compensate for the nuts that were shaken off, the grower makes more money the first year by thinning.  If more nuts are produced the following year than would have been without thinning, the practice pays dividends twice.  Other cultivars, like ‘Stuart’, maintain good quality with big crops, thus thinning can reduce profits the first year, and the grower only comes out ahead financially, if the improvement in yield the second year compensates for the money lost the first year. 

The wholesale pecan market is quite volatile from year to year, due in part to the alternate bearing of pecans.  When the pecan crop is large regionally or nationally, prices are depressed.  The converse is true in light production years.  Growers can come out ahead financially, by crop thinning if they are able to shift their heaviest production to the light years and be “off-cycle” with the national crop.  In that scenario, higher prices in the second year more easily offset the reduction in yield the first year.  Growers who direct market their crop and have more price stability, benefit from thinning by having trees that are more regular bearers from year to year.

‘Pawnee’ is a commercial cultivar that is known to alternate bear badly; however, it tends to make good quality kernels in big crop years and demands a premium price, because it is very early maturing.  We had previously not tested the effects of mechanical thinning on ‘Pawnee’.  One-half of a uniform group of 18 year-old ‘Pawnee’ trees were shaken in late July 1999, to remove 30-40% of the crop.  The other half were not shaken.  Yields were collected from each tree and nut samples were analyzed to determine quality improvement.  Thinning had no effect on kernel percentage in 1999, which meant that dollar value per acre was reduced that year.  In 2000, trees that were thinned yielded 33 more pounds of nuts per tree and dollar value for both years combined was in favor of thinning.