Plant Answers  >  Pecan Nut Drop and Limb Breakage
OH, HELL NO!!
MY LIMBS ARE BREAKING AND MY NUTS ARE FALLING!!

By Larry Stein, Professor and
Extension Horticulturist

It is bad now and it*s going to get a lot worse! Big limbs full of hundreds of pecans are leaning, splitting and breaking on a daily basis. Many people wonder: "Why do these limbs fall?"


Big limbs are breaking and falling
AND IT IS ONLY GOING TO GET WORSE!!!

The reason is far from being clear and in most cases, there can be numerous reasons and, more often than not, is a combination of reasons.
Potential reasons for limb fall include: crop load, "breach" of the bark, wind, maybe drought, trapped bark, "shading out" and age.

Age itself does not necessarily make wood more prone to breakage. The strength of the wood is the same, but the stress and rigor from various outside forces are at play on the tree. As a young tree, limbs are vigorous and strong. It is nothing for the tree to carry 50 to 6 pounds of pecans. As the tree ages, it sets and carries more pecans until one day the limit of some of the branches is exceeded. A branch here and there snaps in two which successfully "breaches" the tree*s protective mechanism of the outer bark. The ideal thing to do when a limb breaks is to saw the rough, jagged broken area smooth in such a way that water is shed and cannot accumulate in the wound. However, this is a difficult task in large trees. On their own, trees will wall off the damaged area. Unfortunately, it is almost impossible for a tree to completely cover a rough area. So over time water accumulates and soon the heart wood (non living portion of the tree has begun to rot). Over time this rotted area grows larger and eventually another limb falls.

 


It is almost impossible for a tree to completely
cover a rough, damaged area to prevent water accumulation.


So the foundation wood of the limb is weakened and breakage occurs.

Realize we are talking about a cycle which may take over 10 years before the actual breakage occurs. In some cases, the initial breach may have occurred 30 years ago.

Pecan has also been accused of having "brittle wood," especially as it
gets older. Where the brittle wood theory comes from is probably due to
"shading out." Pecan is a sun-loving plant and leaves on branches must
receive full sunlight to remain healthy. As trees get larger and
branches begin to touch, the lower limbs receive less and less light and
over time they die! As a result, it is not uncommon for limbs to come
"raining out" of these older trees. So is the wood brittle? Yes, but
only because the limbs were already dead.

Trapped bark can be a problem when limbs form "V" crotches (where limbs
arise from the trunk of the tree). Over time the bark accumulates in
the "V" causing the areas to be weak. A good crop of nuts, leaves or a
wind can bring this limb to the ground again breaching the bark.

Realize that breaches in the bark can occur for many reasons. Hail
can be especially hard on trees. Most times the wounds heal, but a
small hole may remain. Eventually water can make the hole larger, or it
can be gnawed on by a squirrel. Woodpeckers also do their share of
breaching the bark -- what was a small hole gradually increases in size.
Water accumulates in the area and the wood rotting mechanisms are set
in place. Over time squirrels hollow out the area and it grows.

Some limb loss can be blamed directly on crop load; there is simply a
limit as to what a branch can hold. Other losses are from a combination
of factors including the wind, but in the end, it is those small,
seemingly insignificant breaches in the bark which leads to more limb
loss.

THINNING NUTS TO PREVENT BREAKAGE

The goal of growing pecans is to produce quality, well filled kernels.
In the past, pecan growers have tried to produce every nut the trees
set. However, we have found that most varieties are not capable of
filling every nut. Extra fertilizer and water will not allow the trees
to fill all of these pecans. There are simply too many pecans to fill,
or said another way, too many *mouths* (in this case, pecans) to
feed. It takes 6-8 leaves (90-120 leaflets) to fill out one pecan so
the greater the number of leaves on a tree, the greater the potential
production -- up to a certain point.

The key to uniform production is to get all trees to produce crops
every year and not produce a huge crop one year followed by nothing or
little the next year. This phenomenon is referred to as alternate bearing and occurs with most fruit and nut trees which retain and ripen
fruit late into the season. People always complain that they had a
heavy crop of pecans or citrus one year but the following year, they had
little or no fruit production. The tree has to *take a year off*
from the stress of producing a bumper crop. It has to take a year to
get strong enough to produce another good crop.

To determine if a tree*s overloaded, some growers do a visual,
subjective rating where 0 = nothing and 5 = overloaded of the trees in
May and again in early July. This rating can be obtained by counting
the number of terminals (end of the limbs) which have nuts. Count ten terminals on each side of the tree to come up with an average. If all
terminals end in pecan clusters then we know the tree is overloaded and
must be thinned by removing one-half of all clusters of nuts on terminal
growths of branches.

When you have decided to remove some of the nuts, you should remember
that by removing the extra pecans on a tree, you actually insure a
better quality pecan at harvest. The quality of the nuts on a tree with
too many pecans on that tree is very poor and the broken-limb damage to
the tree is permanent. When a tree is overloaded with nuts and limbs
are obviously severely drooping,


A tree is obviously overloaded with nuts when limbs are
severely drooping.


When limbs are drooping so much that pecans are in the
dirt!! you should know you need to thin the nuts!!

remove 50 percent of all the pecan clusters or groups of nuts by
cutting the entire clusters off with hand pruners or shears.


Remove 50 percent of all the pecan clusters or groups of nuts by cutting the entire clusters off with hand pruners or shears.

If the tree is large, use a pole pruner even if you have to rent or
borrow one. The sooner this can be done, the more dramatic the results
will be and the more limb breakage can be avoided. The nuts will
continue to enlarge and get heavier by the day so the sooner you remove
this excess crop, the better. These extra nut clusters should be
removed before the winds of a storm can do permanent damage. Propping
over-burden limbs with poles does not help the situation and only delays
the inevitable as well as ruining the entire crop. The nuts have to be
cut off so the tree can furnish adequate nutrients to the remaining
pecans.

The greatest benefits from removing excess nuts are realized when the
pecans are removed in early July. This not only improves nut quality
but prevents alternate bearing as well. The optimum thinning time is
determined by cutting pecans in half.


The optimum thinning time is determined by cutting pecans in half.

If you cut into the kernel sacs when the nut is cut in two, it is
time to thin the nuts. You will know you have hit the sacs if water runs out of the nut.


When you cut nuts at the optimum time to thin, they will be full of water -- see right side of nut


If there is no water present, there is still some benefit
to pecan quality to remove nuts.

The key is to remove the crop before the trees begin to decline with
leaf loss, shuck decline, and/or broken limbs. Once the leaves begin to drop and/or the shucks begin to blacken, it is too late to improve
the quality of the remaining pecans. However, still removing the extra pecans will prevent major tree damage from limb breakage. If enough
nuts are removed from the trees, percent kernel will be improved and pre-harvest germination reduced.

Another bit of good news: it is thought the stink bug does not cause major damage to pecan kernels until the nuts have passed the water stage. The water stage is when the pecans should be thinned so after you cut one-half of the nuts from your over-burdened trees, start a spray program for your nut crop using a Malathion or Thiodan
(endosulfan) product (organics can use Sabadilla or pyrethrum dust) every 7 days until the shucks (outer green covering of pecan) split.


Stinkbug damage (black spots on kernels) on pecan
halves.

If you thin your pecans NOW and start a stink bug spray program NOW,
you will have plenty of delicious pecans this fall to make some of the best pecan recipes on the face of the earth found at:
/Recipes/pecanrecipes/recindex.html

 


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