Wednesday, October 18, 2017

That one pecan that doesn't open

   Over the past several weeks I've be photographing pecan shuck-split and collecting nut samples. If you look at enough nut clusters like I do, you will usually come across a cluster that has one nut that doesn't seem to split at the same time as all the others (yellow arrow, photo at right). In fact, the shuck stays green and tight all the way until first Fall freeze and never opens. Whats going on here?

   The cluster pictured above yielded four nuts (photo at left). Three of the nuts were easily removed from split shucks. The forth was tightly held inside a green shuck. 

    I cut each nut in half to inspect the kernel within (photo at left). The three normal pecans were fully packed with kernel. The nut with the tight green shuck had the remnants of a kernel that stopped growing at the water stage (early August). Judging from the color of the unfilled seed coat, this kernel was aborted by the tree for some unknown physiological reason.  If the seed coat had been colored jet black, the nut would have been the victim of stinkbug feeding. If the nut had been hollowed out by pecan weevil, I would have found worms inside the green stick-tight. In each case, lack of kernel fill prevents the pecan shuck from opening properly.
   

Tuesday, October 17, 2017

Pecan germination in the shuck

   Vivipary: A ten dollar word that describes the premature germination of a pecan in the shuck during the Fall of the year.  Normally, pecan seeds are fully dormant in October and require a 90-day chilling period to stimulate germination. However, a heavy nut crop and unusually warm, moist, weather conditions during shucksplit can trigger vivipary. In the photo at right, the yellow arrow points to a pecan root emerging from a recently harvested pecan. When a sprouted pecan is harvested and dried under normal harvest conditions, the little root dies and the embryo inside the shell decays. Ultimately, embryo rot totally destroys the value of the kernel.
    Fortunately vivipary is a rather rare phenomenon in northern pecan areas. This year I've found only 2 sprouted nuts among the thousand of nuts I've collected for evaluation this winter. Most years I never see vivipary at all.

Monday, October 16, 2017

Pecan cultivars ripening by Oct 16

Lakota, 16 Oct. 2017
   Today, I took another tour of the grove to look for ripe pecans and enjoy the crisp Fall air and beautiful sunshine. I found five more pecan cultivars with split shucks (at right and below). This year, Giles and Lakota appear to be ripening a little later than normal while Caddo and Maramec have split earlier than normal. Caddo definately appears to have a scab problem even after 3 fungicide applications. Lakota is scab resisitant. The good news is that our spray program gave acceptible scab control on Giles, Maramec, and Mohawk.
Giles, 16 Oct 2017
Caddo, 16 Oct 2017
Maramec, 16 Oct. 2017
Mohawk, 16 Oct 2017


Tuesday, October 10, 2017

Pecan cultivars ripening in early October

Kanza, 7 Oct. 2017
    This week I found 7 more cultivars with split shucks. Many of these cultivars are scab resistant including; Kanza, Greenriver, Hark, Oswego, and USDA 64-4-2. It is so nice to find pecans with clean healthy shucks at the end of the season. In addition, our disease prevention spray program did a pretty good job on limiting the spread of scab on disease susceptible cultivars, Chetopa and Niblack.

Chetopa, 9 Oct. 2017
Greenriver, 9 Oct 2017
Hark, 7 Oct. 2017
Niblack, 9 Oct 2017
Oswego, 9 Oct. 2017
USDA 64-4-2, 9 Oct 2017