Thursday, November 30, 2017

The cost of scab infection

   We've been working hard at harvesting the 2017 pecan crop and I was struck by the obvious impacts pecan scab infection has had on some of our pecan cultivars. At the research station, we have a block of Giles and Chetopa trees, two scab susceptible cultivars. For each cultivar, I collected nuts from the harvester and arranged them by size for a photograph.

    Each photo  shows 3 normal sized pecans in the top row compared to scab-effected,  smaller nuts in the bottom row.  Although both cultivars showed signs of yield loss (smaller nuts) from scab, Giles looks harder hit.
   Looking back at our pecan scab control program in 2017, I think we made an error in waiting for the appearance of pecan nut casebearer before making our first scab spray. As it turns out, casebearer never developed to a damaging level but pecan scab got a good start on our nut crop in early June. I'm becoming convinced that I need to switch our pest control priorities. Next year, I'll time our June pesticide applications based on scab. If that means applying an insecticide a little early for casebearer, so be it. I'll just have to choose a long residual insecticide like Warrior or Intrepid to handle casebearer.