Respectively, associate professor, Department of Plant Physiology and
Pathology, and associate professor, Department of Entomology.
The pecan tree must be protected from attack by the many destructive
diseases and insects that affect it to produce a bountiful nut crop.
The diseases that affect the pecan, especially those caused by fungi,
are rapidly spread throughout the trees in an orchard in the early
spring. During this season of frequent rains, the spores of the disease
fungi germinate and invade the young tender tissues of the shoots,
leaves and nuts. Under conditions of prolonged damp weather, when the
humidity remains high, the disease organisms reproduce at a rapid rate
and cause severe shedding of leaves and nuts.
Pecans are attacked by more than 20 species of insects that cause damage
to leaves, nuts, twigs, buds, branches and even the bark. The
development of commercial pecan acreages has provided ideal conditions
for the increase in severity of both disease and insect damage because
of the abundant food supply in a concentrated planting of pecans. In its
natural habitat the pecan is less subject to the devastations of
diseases and insects.
The many destructive insects and diseases must be controlled for
successful pecan production. The pecan grower must also understand the
nature and habits of the various disease and insect pests that threaten
his crop and use certain cultural practices which help to reduce damage
from diseases and insects.
_Pecan Diseases and Their Control_
The diseases which affect the pecan are of four different types: namely
fungus, bacterial, virus and physiological. The fungus diseases, the
most numerous and widespread, are caused by small microscopic molds.
Approximately 12 different fungus organisms cause harmful diseases of
the pecan.
The bacterial disease organisms, unlike the disease producing fungi, are
single celled and can be seen only under a microscope. Bacterial
diseases are fewer and of less economic importance than fungus diseases.
Virus diseases are caused by extremely small agents which can be seen
only under special ultra-microscopes such as the electron microscope.
Plant viruses are protein substances, but their exact nature is unknown.
Physiological disorders (sometimes called physiological diseases) are
caused by a variety of environmental conditions. A physiological
disorder in a pecan tree may result from infertile soil, excessive
moisture, or the absence or degree of available nutritional mineral
elements to the growing tree. These various environmental factors have
special adverse effects, manifested by specific symptoms caused by
insufficient levels of a given nutritional mineral element or elements,
which are easily corrected by supplying the tree the necessary mineral
elements either through soil application or foliage sprays.