Thursday, November 7, 2013

Scab at season's end

Giles, 4 Nov. 2013
    This past summer we ran some fungicide trials which included a "no spray" treatment. Not surprisingly, fifteen inches of rain in mid-summer helped pecan scab spread rapidly on susceptible cultivars. The photo at right demonstrates what scab can do to the Giles pecan cultivar. The nut the points downward and the nut that point towards the camera will end up in the reject pile as stick-tights. The nuts with open shucks on the right and left sides of the cluster will be harvestable but are smaller in size and not as well filled. All four nuts in this nut cluster were covered in black scab lesions.

Giles, 4 Nov. 2013
      Compare that to Giles nuts treated with three applications of fungicide over the course of the season (photo at left). We didn't get perfect scab control because you can see some scab lesions on nuts at left, but we controlled the disease enough to prevent a reduction in nut size and quality. All of the nuts pictured still had green shucks that had split shucks. Giles nuts tend to stay fairly "closed" after shuck split. After a hard freeze kills the green shuck, the shucks will open up fully. Unlike the scabby nuts pictured above, all of these nuts (at left) will be marketable.
    Scab control this past year was a little tricky. We ended up applying fungicides much later into the season than we even have in previous growing seasons. I was pretty happy with the scab control we achieved. This past season proved how important it is to stay in touch with nut development stage and to make pesticide applications according to the tree's time line rather than the calender date.