The blackberry gallmaker causes the formation of large knot galls on the stems of brambles. The galls are first green and later red or brown. The causal agent is a tiny wasp. If this pest becomes noticeable, remove the galls by pruning, and destroy them. The primary symptoms of the stalk borer in a raspberry field are wilted tips and a large hole in the side of the cane about six to eight inches back from the tip.
Damage is done primarily by boring and tunneling in the stems.
Bramble plantings adjacent to weedy areas of the favored host such as giant ragweed are most often attacked. The stalk borer is a general feeder that attacks stems of any plant large enough to shelter it and soft enough to bore into.