Gray mold in caneberries

Gray mold in Ouachita blackberries. July 2, 2012. North Carolina.

Cultural Practices for Gray Mold Control in Brambles*

Temperatures in June were well below normal and now we are getting above normal amounts of rain. These are ideal conditions for a disease called gray mold. So even though this disease is not usually a problem here in NC, gray mold is showing up in the blackberry plantings. Following from an article that appeared in the Summer 2013 issue of the BRAMBLE, this information is useful for both blackberry and raspberry plantings.

Cultural practices are the major means of control for several important bramble diseases, including gray mold. The following practices should be carefully considered and implemented whenever possible in the disease management program.

• Avoid Excessive Fertilization: Base fertility on soil and foliar analysis. Avoid use of excessive fertilizer, especially nitrogen.
• Control Weeds In and Around the Planting: Weeds in the planting prevent air circulation and result in fruit and foliage staying wet for longer periods. Controlling wild brambles (which are weeds) near the planting is also important because they can serve as a reservoir for several important diseases and insect pests.
• Practice Sanitation (Removal of Overwintering Inoculum): Pruning out all old fruited canes and any diseased new canes (primocanes) immediately after harvest and removing them from the planting breaks the disease cycle and greatly reduces the inoculum.
• Manage the plant population and canopy to increase air circulation and exposure to sunlight: Ideally, rows for red raspberries should not be over 2 feet wide and contain about 3 or 4 canes per square foot. Specialized trellis designs for Rubus spp. can further improve air circulation and increase exposure to sunlight, as well as increase harvest efficiency. Trickle irrigation, (vs. overhead sprinkler irrigation), greatlyreduces wetting of foliage. Removing young fruiting shoots (before 4 inches long) from the lower 20 inches of canes will remove fruit that might become soiled.
• Adjust Production Practices to Prevent Plant Injury and Infection: Many plant pathogens take advantage of wounds in order to penetrate and infect the plant. Using sharp pruning tools will help minimize damage to canes during pruning operations. Prune only when necessary (avoid cosmetic pruning of primocanes) and avoid pruning during periods when plants are wet or immediately before wet weather is forecast. Provide proper cane support through trellising or otherwise tying the canes to in avoiding abrasions from sharp spines and wind whipping of plants during windy conditions. Proper spacing between rows and the use of the proper size equipment will also prevent plant damage.
• For chemical control options see the SRSFC IPM guide, pg 24 (and 15) http://www.smallfruits.org/SmallFruitsRegGuide/Guides/2013/2013BrambleSprayGuide6_17_2013.pdf

*Copied from the Bramble Newsletter, which was edited – because of space limitations – from a much longer article by Mike Ellis & Mizuho Nita, Ohio State

University. See the full article at www.fruit.cornell.edu/nybn/newslettpdfs/2013/nybn1205a.pdf.