Kernel necrosis is a malady characterized by necrotic tissue at the basal end (stem end) of the kernel (Fig. 1) (Smith et al., 2007). It was first reported in an orchard near Charlie, TX, and has since been identified in several orchards with ‘Pawnee’ trees located in the Red River Basin located along the Oklahoma and Texas border (unpublished observations). No symptoms of kernel necrosis were visible on the shuck (involucre), although the intact fruit appeared slightly larger than normal fruit. Kernel necrosis was more prominent on ‘Pawnee’, ‘Choctaw’, and ‘Oklahoma’ and rarely, if ever, occurred on other observed cultivars (Smith et al., 2007). At maturity, nuts (pericarp and cotyledons) with kernel necrosis had a larger shell volume than nuts with normal kernels. The orchard near Charlie, TX, received unusually large amounts of nitrogen (N) from a combination of the producer's applications (112 kg·ha−1 N in March and June plus 84 kg·ha−1 N in September) and nitrate (NO3) -contaminated irrigation water (≈160 kg·ha−1 N annually). Accumulated NO3-N in the upper 45 cm of soil was 197 kg·ha−1 N in 2006 with a July leaf N value of ≈2.8%. During a 5-year study, the average percentage of kernel necrosis ranged from ≈1.4% to 22.2% of the crop, but individual trees sometimes had a much larger percentage of kernel necrosis. It was hypothesized that excess N was involved in kernel necrosis; however, a 5-year N rate study found no relationship between N application and kernel necrosis (Smith et al., 2007). Supplemental foliar applications of copper and nickel also failed to affect the incidence of kernel necrosis (Wagle et al., 2011).
Producers in the Rio Grande Basin near El Paso, TX, reported an unidentified problem on ‘Pawnee’ kernels in 2011. Samples from selected orchards near El Paso were evaluated for kernel necrosis along with samples from northeastern, southern, and central Oklahoma and northern Texas orchards. Occurrence of kernel necrosis from additional orchards is reported here. Results of studies of the relationship of kernel necrosis with crop load, tree size, and its distribution in the tree canopy are reported.
Draper, N.R. & Smith, H. 1966 Applied regression analysis. Wiley, New York, NY
Wagle, P., Smith, M.W., Wood, B.W. & Rohla, C.T. 2011 Supplemental foliar nickel and copper applications do not reduce kernel necrosis in pecan trees receiving excess nitrogen Commun. Soil Sci. Plant Anal. 42 2219 2228