Pecan leaves can start to show symptoms of minor disease in the late season. Most of the time, it’s nothing to worry about. These foliar diseases won’t defoliate the trees in the next few weeks. The leaves are beginning to senesce anyway. UGA Extension Horticulturalist Dr. Lenny Wells has information on one of these issues:
One of these raising its head (now) is a relatively new disease we began seeing just 4 or 5 years ago. Symptoms are expressed initially as a dying or browning of the terminal leaflets on a compound leaf which progresses backward toward the base of the leaf. Eventually it moves into the leaf rachis (the main stem of the compound leaf) and the entire compound leaf may die. If you stand back and look at a tree infected with this disease the scattered dead compound leaves will look like dead brown patches in the tree. UGA research pathologist Tim Brenneman has identified this as a fungal pathogen called Neofusicoccum. I will be referring to it as “terminal die-back.”
Most minor foliar disease like this infect the leaves a month or two prior to symptom expression. Dr. Brenneman suggests use of a strobilurin or a DMI/strobilurin mix like Absolute or Quadris Top when conditions favor infection (usually prolonged wet conditions). Even if a grower has used these materials, their timing may have been off enough to allow infection. Once you see the symptoms its too late to do anything about it. But, even when terminal die-back occurs earlier in the season we have not seen any long-term damage to the trees and no effect on nut quality so don’t get too alarmed when you see this problem.