PECANS ARE FALLING.

PECANS ARE FALLING.

            I have written about this before, but I am getting questions so I thought I should publish this again.  Pecan nuts grow in two phases.  The first phase includes pollination, nut enlargement, and water stages.  This usually occurs between the dates of May 1 to August 15.  Phase II is kernel filling and shell hardening.  This usually occurs from August 15 to November 1.  Close to the date when the first phase of nut development is complete, the third nut drop, called the August drop occurs.  This usually occurs from August to mid-September sometimes it goes into October. It causes greater concern to pecan growers and homeowners because of the large size of the nuts at this time.  Although the percentage shed is generally low, 8 to 10 percent.  Some trees in the area this year have had higher percent shed however.   Embryo abortion is considered to be the reason for this late drop.

            By the time August drop takes place, the embryo has attained full size, the ovary has about completed its enlargement and the pecans will soon begin to harden.  Cutting into the pecans they are still wet however.  Premature shedding will occur when something affects the embryo.  If the embryo aborts after the shell hardens, the nut usually matures, but will be hollow or what is commonly called a pop.  Although the causal factors for embryo abortion are not known, some researchers consider the following situations, to be related to embryo abortion:

•                  A severe drought or later stress.  This is more likely to occur in poor soils and it frequently takes place during the water stage.

•                  A prolonged period of excess moisture.  Lack of air in the soil impairs the root system capacity to absorb water and nutrients required by the pecan tree.  Happen when we get a lot of monsoonal moisture, not an issue this year

•                  Hot, dry winds can increase water loss by increasing the pecan tree moisture requirements due to high transpiration rates.

•                  Insects (Shuck-worm, southern green stinkbug, pecan weevil).  Puncturing of the ovary wall, the future nutshell will cause nuts to fall in 3 or 4 days.

•                  Any physical damages that can disturb the ovary wall (shell) of pecans.  This can be birds, bugs, a lot of things. 

            The fact is we really don’t know, that why we say “something” and we make or best guess.  I personnel think it could be low nutrition.   Justus von Liebig's Law of the Minimum states that yield is proportional to the amount of the most limiting nutrient, whichever nutrient it may be.  So if you have not collected your leaf sample for analysis and you have a large nut drop, you might consider doing it. 

            In general this has been a stressful year due to the changes of temperature cool then hot, and water requirements of the trees.  Rainwater not only helps supply water to the trees it also has a higher leaching capacity for leaching salts from around the roots.  Salt can cause a physiological drought in the trees, which cause embryo abortion.    Look at a sampling of the fallen nuts and check for insect damage to the shuck or the shell.  Pecan Weevil has increased its territory in Texas so if you find a whole in the nut and a grub inside contact that to the Extension Office.

            If you are having a high August nut drop, all you can do is water correctly, not to much, and not to little and take care of the crop you have left, send a leaf sample to a lab for nutrition assessment so you may take corrective action before next years crop.  Subscribe to Eddy County Ag news at: http://nmsueddyag.blogspot.com/  Eddy County Extension Service, New Mexico State University is an equal opportunity/affirmative action employer and educator.  All programs are available to everyone regardless of race, color, religion, sex, age, handicap, or national origin.  New Mexico State University, U.S. Department of Agriculture, and the Eddy County Government Cooperating.