Three non-chemical approaches to pecan pest management are choosing an adapted pecan variety, keeping the soil moist and fertile, and conserving beneficial insects.
Adapted varieties: One of the most important decisions in growing pecans is choosing a pecan variety that is adapted to the climate of your region of the state. Also, look for adapted varieties that are less susceptible to pecan scab, a serious fungal disease that attacks leaves and nuts. For a list of varieties adapted to different regions of Texas, including their susceptibility to scab, check the map (Fig. 1) and refer to the Texas AgriLife publication Texas Fruit and Nut Production: Improved Pecans, which can be found at http://www.agrilifebookstore.org/.
Soil moisture and fertility: Providing adequate irrigation and soil fertility can help the trees grow vigorously and defend against insect and disease attack. For instance, trees under drought stress are especially vulnerable to infestation by tree borers. The Improved Pecans publication, referenced above, provides guidelines on growing pecans in Texas.
Beneficial insects: Predatory and parasitic insects that attack pecan insect pests include assassin bugs, lacewings, lady beetles, predatory mites, spiders, and many kinds of tiny wasps that parasitize insect pests (Fig. 2).
These beneficial insects exist naturally and can help reduce pest numbers. Conserve their populations by minimizing insecticide applications and using selective insecticides that control the pest with minimal damage to natural enemy populations. As examples, spinosad and B.t. formulations are less toxic to most beneficial insects and other non-target species than are broad-spectrum insecticides such as esfenvalerate and other pyrethroids. However, research has shown that buying and releasing lacewings, convergent lady beetles, or Trichogramma wasps does not provide significant pest control in pecan.
Figure 2. Common beneficial insects (clockwise from top left): lacewing egg larva, and adult (photos by Whitney Cranshaw, Colorado State University (egg), Salvador Vitanza (larva), Johnny N. Dell, Bugwood.org (adult); harmonia larva (photo by Bill Ree, Texas A&M AgriLife Extension Service); wheelbug adult (photo by Bill Ree, Texas A&M AgriLife Extension Service); and Asian lady beetles (photo by Bill Ree, Texas A&M AgriLife Extension Service).