What to watch for: Raspberry cane borer

Damaged blackberry primocane at the Sandhills Research Station, May 23, 2011.  Photo: HJB

While checking our virus vector monitoring plots today at the Sandhills Research Station, near Jackson Springs, NC, I noticed a few plants with classic raspberry cane borer injury.  Female raspberry cane borer beetles lay their eggs near the tip of primocanes causing the end to wilt and creating a distinctive, paired girdling of the cane.

Raspberry cane borers are one the many exciting "boring" insects that feed on caneberries in the southeast.  If left unchecked, the larvae can kill the cane they feed on over the course of 1-2 years, depending on where in the US they are.  In North Carolina, these insects probably have a 1 year larval life cycle.

The injury at Sandhills was very recent, as evidenced by the fact that the end of the cane was just wilted and not dead.  In addition, no larvae were readily found in the cane when I tore it open, suggesting that the eggs have not yet hatched.

Cultural control, via removal of infested canes, is the recommended management strategy for both raspberry and rednecked caneborers, and this is the perfect time to remove raspberry cane borer infested tissue!  Infested primocanes can be tipped, and will continue to grow over the course of the summer.  If left until fall, during the typical pruning period, the entire damaged cane must be removed to ensure the raspberry cane borer larva is destroyed.  Neither raspberry or rednecked cane borer injury typically damages more canes that would be removed through typical fall/winter pruning in North Carolina.  We generally only see significant raspberry or rednecked crown borer injury at locations where pruning has been minimal.  Now is a good time to scout for borers are remove the damaged plant parts before they can get a foothold.

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