Certain conditions can cause premature drop of pecans. Due to cultural problems, infestations or infection, fruit drop is a severe case of damage that occurs due to an underlying health concern. Familiarize yourself potential problems and control methods for vigorous pecan trees and healthy fruit.
Pests and diseases are less likely to affect healthy trees than weakened or stressed plants. For vigorous growth, plant pecan trees in an area with full sun exposure; keep trees planted at a minimum of 30 feet from structures like homes or other buildings to avoid unwanted shade, according to the AgriLife Extension Texas A&M System. Grow pecan trees in moist, well-drained soil for optimal fruit growth.
Normal Fruit Drop
Fruit drop of healthy trees is a normal occurrence when nuts have reached maturity and are ready for harvest. Pecans are generally harvested from October to December and can be shaken from the tree through mechanical means, such as with the assistance of a tractor, before they fall on their own, according to the AgriLife Extension Texas A&M System. When the covering, or shuck, of the pecan begins to open naturally, pecans falling from the tree is nothing to worry about.
Pest infestations are often responsible for early fruit drop from pecan trees. The hickory shuckworm (Cydia caryana), for example, infests pecan trees, resulting in premature fruit drop, according to the University of Missouri Extension. Shuckworms lay their eggs on pecan fruit shucks and the larvae hatch and invade and feed on the nut. Hickory shuckworms are cream in color with white heads in the larval stage and, as dark brown pupae, they live within the pecan fruit.
Pecan scab (cladosporium caryigenum) is a disease of the pecan tree that causes premature fruit drop, according to the University of Missouri Extension. Scab is a fungal infection that attacks leaves and spreads throughout the tree. Look for muddy green spots that become black on leaf surfaces, as well as shucks. These spots often grow and join together to form abnormal lesions; affected areas also die, leaving a hole in their wake.
For control of fruit drop from pecan trees, apply an insecticide to kill shuckworms. Apply the insecticide during the middle of August as shells are hardening. For pecan scab management, plant resistant pecan tree varieties such as Barton or Green River, advises the University of Missouri Extension. Apply a preventive fungicide, such as benomyl, in a mixture with a non-benomyl fungicide.