Monitoring scab

Native pecan infected by scab

     The 2017 growing season started off with ample rainfall and ideal conditions for the spread of pecan scab (photo at right). In response, we have made two fungicide applications this summer (Mid-June and early July). However, the weather in our area has turned off hot and dry and the spread of the disease has slowed dramatically.
     We got a late start in spraying for scab this year because I kept waiting for pecan nut casebearer to appear (it never did) before making a trip through the orchard with my sprayer. As a consequence, we have a light scab infestation on susceptible cultivars.

   In looking at several cultivars, I found that most scab susceptible cultivars have a non-damaging levels of scab on the shucks. The Giles nut cluster pictured at left is a good example of how our less that perfect scab control efforts have held disease spread to a minimum.

   

    Of course, a scab free cultivar like Kanza looks perfect at this time of year (photo at right). However, it is worth mentioning that Kanza does benefit from receiving fungicide applications. Kanza may be resistant to scab but it is susceptible to pecan anthracnose which can cause fungal leaf scorch and shuck rot.

    I also looked at Mandan to confirm my assertion that this fairly new pecan cultivar is susceptible to scab (photo at left). It appears that Mandan is not super-susceptible to scab but will definitely require a fungicide program to ensure top yields.