Friday, June 5, 2015

Mandan performance in northern pecan states

    Mandan is a relatively new pecan cultivar that, on paper, looks perfect for northern pecan growers. In past blog posts, I have voiced my concerns about this cultivar in terms of nut quality and scab susceptibility. This past winter, we were able to look at Mandan nut samples grown in three northern pecan states (photo at right).

    Results from of last winter's nut evaluations for Mandan are given in the table at right. When I compared the numbers in the table with the photo above I was surprised to find that the large Missouri nut had the lightest nut weight. It seems that Mandan nuts have such a thin shell that total average nut weight is largely determined by how well a Mandan tree can fill kernel (look at the differences in % kernel).

   Mandan produces a kernel with some serious defects. The Mandan sample from Kansas produced the best kernels of the three samples evaluated (photo at right). Looking carefully at these pecan kernels I find five problems.
  1. The dorsal groves are narrow and deep and can often trap inner-shell material.
  2. Every kernel produced a dark colored flap of seed coat at the end of the kernel (marked A).
  3. The kernel has prominent dark veins (marked B).
  4. The surface of the kernel is wrinkled, giving the nut meat a shriveled appearance (marked C).
  5. A dark spot often appears on the underside of the kernel (marked D) that is not insect related.

    The Missouri Mandan tree suffered from an extended dry period during mid-summer, giving us the opportunity to see how kernel quality is impacted by drought. Dry weather caused the Mandan kernel to be smaller, more wrinkled, and darker in color (photo at left). What is hard to see in the photo is the fact that the underside of the Missouri Mandan kernel is deeply depressed due to poor kernel fill.
    If you are interested in producing quality pecan kernels, I would avoid grafting Mandan into your orchard.