Tuesday, November 6, 2012

Giles ripening effected by crop load

    Thirty years ago, Giles was one of the most popular cultivars to propagate in Kansas. Selected from a native grove outside of Chetopa, Giles seemed like the perfect pecan for our growing under our conditions. But grow any cultivar long enough and you'll discover you still haven't found the perfect pecan cultivar.
    Giles has a tendency to over-produce. This leads to all the typical problems associated with alternate bearing including poor kernel quality during "on" years and next to zero crop during "off" years.  However, this year we've seen a new problem with our Giles trees--incomplete ripening.  A quick survey of Giles nuts still hanging from the tree reveals that some nuts have split shuck normally while others have not opened at all (photo above, right). At this point in the season, the nuts have have failed to split, will never open.
     I peeled out some of the "stick-tight" nuts  and cracked open the shells to see if poor kernel development was the reason for lack of proper ripening (like we saw with Posey). In every case, the kernel in the sticktight nuts were just as well filled out as nuts that ripened properly.  Something else was causing sticktights.

    Earlier this summer we recorded the amount of fruiting shoots produced by 20 of our Giles trees. These counts revealed a wide variation in crop load. We had Giles trees with as low as 16% fruiting shoots to as high as 70% fruiting shoots.  To see if crop load influenced the amount of incomplete ripening found on a Giles tree, I decided to climb into the hydraulic lift and make some nut counts.  My results can be seen in the graph above. The heavier the crop load (greater % fruiting shoots) the more incomplete ripening or stick-tights we found in the trees.
    Incomplete ripening due to fruiting stress may occur in other cultivars but it is most pronounced with Giles. The drought we experienced this past summer may have also contributed to making the problem worse in 2012.