- Author: Mark Bolda
A couple of pictures below from a farm call concerning unusual damage on the tips of growing raspberry. Some of the leaves are affected as in Photo #1, but others are pretty well aborted and not growing at all. Incidence wasn't more than 5%, but still this is disconcerting and I was over at the grower field within 15 minutes to take stock of the situation. No flowers or fruit yet on the plants.
No signs of frass or webbing that would be associated with leafrollers (some like to feed at the nitrogen rich tips), and I've checked this sort of thing in caneberries before and haven't found that viruses or nutrients are at cause either.
But we did find lygus and Photo #2 explains that we may have identified the cause. While some lygus were to be found wandering around on leaves, others were nestled in the growing point of the plant, which on the very young leaf can show up as a lot of damage later on when it fully expands. It's quite possible that this insect activity could be causing the tip to die entirely in a situation reminiscent of "black flagging" in cotton, which is the death of terminals in cotton caused by lygus feeding.