Managing blackberry harvest and health in the midst of a rainy and cool season UPDATED 7/11/13
In light of the wet weather and the forecast of more wet weather and a possible tropical storm next week, I asked for some recommendations from Specialists around the region. Here they are, I will update and welcome comments.
Dr. Carl Crozier, Soil Science, NC State University
Nitrogen management could be even more unpredictable than usual. Depending on timing of N, the nature of the soil profile, and the crop management (including mulching) system; excess water may have enhanced deeper N movement and/or N runoff or denitrification losses, and an elevated water table may have restricted crop rooting. Plant tissue analysis could be useful in assessing crop status.
Dr. Gina Fernandez, Horticulture, NC State University
Yesterday, I was at a blackberry farm in eastern NC. They were using a radar app (My Radar) to help determine when rain was coming. They were dodging rain showers the entire time, and with the help of the app they could determine if they should run a load of fruit into the packing shed, unload and by the time they were unloaded the shower had passed. There are several other apps that can pinpoint your location, so see what works best for your farm.
Another observation was that they said they would pick the fruit as long as the rain is not dripping off from the ends of the fruit. They also were covering the clamshells in the field with a layer of plastic to keep the rain out of the clamshell off the berries.
When you are tipping the primocanes, the smaller the diameter of the cane at pinching will minimize the potential for cane blight infection. If you have to use a pruners, a fungicide should be applied soon after the canes were cut. For more information see http://teamrubus.blogspot.com/2012/06/blackberry-tipping.html
Be sure to remove spent canes as soon as the fruit is harvested. Good air movement will be important to minimize disease pressure.
Dr. Penny Perkins, Post Harvest Handling NC State University
We’re finding the (rotating arm) trellis is helping greatly with fruit quality in this rain. I see a lot less ‘bleed out’ as rain sits far less on the fruit. What the eastern NC grower is doing is very similar to what we’re doing-dodging showers. We’re finding that the droplets from the wet fruit condense on the top (inside) of the clamshells, which for us is not a problem since we transfer to pints later. I would think that placing clamshells in the cooler then turning on fans to move air would help more than anything to evaporate the condensation.
Although these high rainfall years are unusual, the trellis is proving itself to be a huge asset in boosting berry quality (less soft, less bleaching, less sour fruit, and much better fungicide contact on fruit itself).
Dr. Hannah Burrack, Entomology, NC State University
SWD is the greatest insect concern because rain limits both the ability to apply insecticides as well as their residual activity. I put a post on the strawberry portal this year discussing this issue:
In blackberries, Mustang Max has shown some decent residual activity following rain, so that would be the material I’d use if I anticipated a rainy week ahead. Delegate might be another option, but we have less information on its rain fastness.
Also important is good sanitation after rain. Fruit that is on the overripe side has been exposed to SWD longer and at greater risk of infestation. Overripe fruit is also softer, making it potentially more attractive to SWD. This fruit should be removed before harvest so that it doesn’t make it into a clamshell.
Dr. Phil Brannen, Plant Pathology University of Georgia
Tell them to review the IPM spray guide at www.smallfruits.org. http://www.smallfruits.org/SmallFruitsRegGuide/Guides/2012/2012BrambleSprayGuide.pdf
Botrytis is the primary driver of their spray program at this point, but leaf spots and cane diseases will increase with this weather. Without knowing more, I would suggest Switch for the next couple of applications. We are observing substantial resistance development with other Botryticides, but at least one component of Switch will work. They should send Botrytis samples to Clemson University for resistance profiling. This will help them to better address which fungicides are active for the remainder of the season. Turnaround is 72 hours.
Dr. Guido Schnabel, Plant Pathology, Clemson University
Yes, we are able to process botrytis samples and screen for sensityvity to 7 classes of fungicides. See previous blog post: http://teamrubus.blogspot.com/2013/04/monitoring-of-fungicide-resistance.html
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