Mysterious spots on tunnel raspberries

An Extension agent found these spots on tunnel raspberries last week. The fruit has been sent to the clinic for identification. We have a couple of theories on what it may be, and will let you know what it is as soon as we receive confirmation.

Blackberry pinching/tipping

When primocanes reach 3-5 ft, they need to be pinched or tipped (see top photo above). Pinching does two things. First, it maintains a manageable canopy height. Second, it  will enable the canes to produce laterals. These laterals will produce fruit next year.

The ideal diameter to pinch is small enough so you can remove it easily with your hands and not use a pruner. Wider diameter cuts that need a pruners create larger wounds. These large wounds do not heal as quickly and are therefore more prone to infection. The middle photo above shows a cane before tipping and the bottom photo shows the same cane after it has been tipped.

The primary disease that occurs as a result of the larger pruning wounds is Cane Blight. Cane Blight of Blackberry, is caused by Leptosphaeria coniothyrium. For more information on this disease see Dr. Phil Brannens publication at http://www.caes.uga.edu/publications/pubDetail.cfm?pk_id=7380.

Blackberry season approaching

Yesterday I visited 2 blackberry farms. One of the farms has a "Shift Trellis." This type of trellis is moved to different positions through the season. In the spring before buds break it is placed in a horizontal position so the fruiting laterals grow toward the sun, all on the same side of the canopy. Once the fruit has set, the trellis is shifted to about a one o'clock position, so the fruit faces the afternoon sun. Here is a picture of the fruit in the green stage.