Kernel Necrosis of ‘Pawnee’ Pecan: Expanded Distribution and Relation to Yield, Tree Size, and Canopy Location

Abstract

Pecan [Carya illinoinensis (Wangenh.) K. Koch.] kernel necrosis is a malady characterized by development of a dark necrotic area at the basal end of the kernel. This problem is particularly severe on ‘Pawnee’ at some locations during certain years. Currently, the cause of kernel necrosis is not known. Initially, this problem appeared confined to certain cultivars in a north Texas orchard in the Red River Basin and ‘Oklahoma’ in a central Oklahoma orchard adjacent to the Deep Fork River. After El Paso, TX, producer reports of an unknown problem on ‘Pawnee’, mature nuts from orchards near El Paso, north Texas, and southern, central and northeastern Oklahoma were evaluated for kernel necrosis. Kernel necrosis was abundant on ‘Pawnee’ nuts from El Paso and southern Oklahoma, moderate at the north Texas site, and at low levels in one northeastern Oklahoma orchard. None was found in two ‘Pawnee’ orchards, one in central Oklahoma and the other in northeastern Oklahoma. In another study, yield was monitored on hedge-pruned ‘Pawnee’ pecan trees over a 5-year period to determine the relationship with kernel necrosis. The incidence of kernel necrosis was greater when yield was less. A third study sampled nuts from the lower and upper one-third of canopies from randomly selected trees varying in trunk size. Kernel necrosis frequency was similar in the upper canopy among different trunk sizes, but the incidence in the lower tree canopy decreased as trunk size increased.