Sunday, September 27, 2015

Scab on 'Mandan' pecan

    The cultivar release notes published when Mandan was first made available to the public claimed that nuts produced by this tree are resistant to pecan scab. Although not extremely susceptible to scab we have found Mandan shucks infected with the disease.
    This past season we applied a fungicide three times to our Mandan trees during the months of June and July. For the most part, we have kept the shucks mostly clean with only a few small scab lesions appearing by late summer (photo at right).

   However, where we didn't get good fungicide coverage on the nuts, I found several clusters of Mandan nuts covered with scab lesions (photo at left). Mandan also seems to be susceptible to powdery mildew.
    While taking this photo of scabby nuts, I found a crab spider resting on one of the nuts. Crab spiders are a common insect predator in pecan tree canopies with female spiders often hiding their eggs at the base of nut clusters.