Wednesday, August 21, 2013

Pecan scab infection decreases nut size

Giles nut clusters with and without fungicide sprays

    It's been several years since we've had the weather conditions needed to promote the spread of pecan scab. However, the four weeks of rainy weather we experienced this year during late July and early August was prefect for promoting scab infections. Scab susceptible cultivars that were not protected with applications of fungicides are now covered with scab lesions.
    Two clusters of Giles pecans are pictured above. The cluster on the left received two fungicide applications this summer. The nuts on the right were not sprayed with a fungicide at any time this year. Besides covering the shuck with black lesions, scab infection during the nut sizing period has had  dramatic impact on nut size. The scab covered nuts are nearly one half the size of the healthy nuts.
    This fall, the yield losses due to scab infection on untreated Giles trees will be immense. Scab will increase the number of harvested sticktights, shrink average nut size and reduce percent kernel. Yes, fungicides are expensive but growers that made well timed applications will be rewarded with more pounds of high quality nuts this Fall.