Managing raspberry cane borers this fall

Article originally written by Annie Klodd, former UMN Extension Fruit Educator, updated in 2026 by Madeline Wimmer.

Raspberry cane borer (Oberea perspicillata, also cited as O. bimaculata) is an occasional pest of raspberries in Minnesota. This borer causes the growing tips of raspberry canes to wilt and fall off as the adults chew two rings of holes, or punctures, in the canes during egg laying.

Raspberry growers can scout for this damage in the fall and remove any canes with cane borer damage. Doing so is an effective management strategy to remove most or all of the larvae present.

Images: Raspberry cane borer larvae tunnels seen directly below the puncture holes. Photo by Annie Klodd.

Recognizing Cane Borers and their Damage

Raspberry cane borer larvae are small, thin and light in color. They can be seen feeding their way down the inside of raspberry canes if you were to cut open an infested cane lengthwise.

The adults are active from late June to early July. They are black beetles with a long and thin body and a patch of yellow between the main part of their body and their head (the thorax).

At this point in the season, it is most important to be able to recognize what their damage looks like so that you can remove the infested canes. 

• Look for primocanes where the tips wilted and died mid-season. 
• In some cases, the tips may have fallen off altogether by this point. 
• At the point where the cane tip died, look for two rings of punctures (usually 1/2 inch a part). This is what causes the tips to wilt.
• If you cut into the cane slightly below the puncture holes, the cane should contain a hollow tunnel where the larvae has been feeding.
• The infested canes may be stunted and short because their apical growth was stalled mid-season.

Red flag: If a cane is completely dead from the base level, that could be due to a number of things including diseases; at that point you should consult the Plant Disease Clinic about submitting a sample for diagnosis.

Two sets of puncture holes girdling the primocane, created by adult raspberry cane borer. Photo: University of Kentucky.

Knowing their life cycle can help you manage cane borers

Something helpful to keep in mind about raspberry cane borers is that they have a two-year life cycle. 

Scouting for egg laying adults: Start scouting for adult beetles on the plants in mid-June and continue through mid-July. 

From late June through early July, the adults lay eggs on the young, new canes, about 4–6 inches from their tips. After laying the eggs, they puncture a set of small holes around the perimeter of the cane. This puncture damage is what actually causes the top of the cane to wilt. 

Larval emergence: Then, the larvae emerge from their eggs in July, burrow into the canes, and eat their way down for a few inches into the first winter. During the following year, they continue feeding down the rest of the cane and into the crown, and they overwinter the second year at the base of the cane near the roots. The next spring, they pupate and eventually emerge as adult beetles, beginning the lifecycle over again.

Managing Raspberry Cane Borer Without Insecticides

Growing season management: The main way to manage cane borers takes place during the summer and does not involve insecticides. When you first see a cane that is wilting or dead near the top, look for those puncture holes mentioned above. If they are present, cut the cane about 2 inches below the holes. Then remove those cuttings from the field and destroy or dispose of the cuttings.

Fall management: Even though we are moving into the dormant season, you can still cut the infested canes now; this will likely remove some or most of the larvae, because the larvae spend their first winter in the canes. It is considered acceptable to just cut the cane a few inches below the puncture holes if you want to harvest from the floricane next season, or to remove the whole cane.

Note on chemical management: Insecticides are usually unnecessary for cane borer control. The problem is rarely bad enough for insecticides to be economically beneficial. In other words, think about whether the cost of application is worth what you will save in terms of plant health or yield. In most cases, the answer is no, because the damage is minor and infested canes still produce fruit from lower laterals.

Additional Reading: 

• Controlling Raspberry Cane Borers - Michigan State University Extension
• Raspberry Cane Borer - University of New Hampshire Extension