|My ever-bearing raspberry canes have developed a ring on them. Could you tell me what causes it and how to take care of it?|
|Your description of the problem is too brief for me to make an absolute diagnosis, but attack by the raspberry cane borer on blackberry, raspberry and rose results in tip die back and cane death. Damage is readily identified with this insect by two rings of punctures about 1/2 inch apart and located 4-6 inches below the growing tip. These girdles cause the tip to wilt. Damage becomes more profound as the larva burrows to the base of the cane, causing the entire cane to die before the fruit matures.
The raspberry cane borer is a slender long-horned beetle measuring about 1/2 inch long. It is black in color except for a yellow-orange thorax with two or three black dots and has long antennae. The elongate, cylindrical, legless larva is white and attains a length of nearly 3/4 inch.
Raspberry cane borer adults appear about June and after puncturing the two rings in the canes, lay an egg between the rings. These hatch in July and the larva begins burrowing towards the base of the cane and overwinters about 2 inches below the girdling. The second season it continues to burrow downwards to ground level where it spends the winter. It emerges as an adult the following spring.
The planting should be examined weekly during June and July. The existence of wilting tips characterized by the two rings described earlier identify attack by raspberry cane borer. Control is obtained by pruning out the infested canes by cutting a few inches below the oviposition rings or below the larval tunnel.
Hope the above information helps you save your raspberry plants!