Q.
I had two pecan trees that are now 25 years old. One variety has round nuts and
the other one has oblong nuts. This is the first year in 25 years they have
produced nuts that have black spots and are bitter tasting but the outside of
the nut looks normal. Any idea what the problem might be?
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| Pecan scab. Picture from Texas A and M University. |
A.
Pecan nut problems are hard to diagnose. The nuts themselves can be bitter if
some of the husk is attached to the nut. But yours sounds like a disease issue
to me. Perhaps it was our wet early summer and spring that created the problem.
The most common disease of pecans is scab.
When it is a wet spring, after a rain, it is wise to spray the trees in March
with a fungicide such as Bordeaux or copper sulfate. If it rains again, spray
it again after the rain has stopped. The problem is spraying these trees top to
bottom since there are no systemic fungicides that can be applied to the soil
and taken up by the roots. The lesions on the outside surface of the shell this
disease produces are difficult to see and does produce an “off flavor” once
inside the meat.
I must guess a little bit, but the
varieties popular about 25 years ago in the West were oblong nut varieties
called “Western Schley”, “Mahan”, “Wichita”, “Mohawk”, and “Cheyenne”. The
older and round nut varieties were either “Burkett” or possibly “Choctaw”. The
reason I mention it is because there are probably well over a hundred varieties
of pecan. The more recent hybrids are smaller, produce nuts sooner, less likely
to bear nuts every other year (alternate bearing), and don’t need a pollinator
tree. Also “Choctaw” and “Cheyenne” varieties were considered “resistant “to
this disease.
Even though pecan trees can handle our
summer heat and poor soils, I don’t recommend them for our area because of
their size and water use. Pecan trees can get big, growing 60 to 100 feet tall
and 30 to 50 feet wide, and have no semi-dwarf or dwarf varieties that I know. Their
size dictate they use a lot of water. They do have a sizeable tap root so they
possibly could be used where there is shallow underground water.