Asked June 23, 2015, 11:48 PM EDT
Clackamas County Oregon
Your fruits may be affected by redberry mites. These mites are very tiny and are quite different than the more common spider mites. They survive the winter underneath the bud scales. Sprays must be used while the fruit is still green.
In home gardens, choose between lime-sulfur and a superior-type horticultural oil. Apply lime-sulfur to the canes in spring when vegetative buds are about a half-inch long; repeat application in the fall. Or apply a superior-type oil and apply when floricane lateral growth (fruiting growth) are 2 to 6 inches long; a fall application is optional. If you have not used horticultural oils on your blackberry plantings before, it’s wise to test it on a small portion of the planting first, to check for possible damage from the oil. Several more cautions include these: Don’t apply oils within one month of treating with sulfur; And don’t apply oils when temperatures exceed 90 degrees.
Because of our recent mini-heatwaves with clear skies, we need to be certain this is not sunscald. In this case, the affected drupelets (individual fruit cells) on the sunny side of the berries turn white. They eventually dry and turn brown.
Resources for you:
Growing Blackberries in Your Home Garden - https://catalog.extension.oregonstate.edu/sites/catalog.extension.oregonstate.edu/files/project/pdf/ec1303.pdf
Growing Raspberries in Your Home Garden - http://extension.oregonstate.edu/deschutes/sites/default/files/ec1306.pdf