Making a comeback- revisiting raspberry crown borer control
Pam Fisher, Berry Crop Specialist, OMAFRA
Raspberry crown borer (RCB) is a sneaky pest that attacks raspberry crowns. Larvae tunnel and feed in the crown for up to two years. As a result, fruiting canes are weakened, and primocanes become scarce and spindly over time (Figure 1). Because these symptoms could have a variety of causes, raspberry crown borer is often overlooked.
Figure 1 - RCB - damage to field
In the past, growers have managed this pest with a well-timed spray of an organophosphate insecticide directed to the base of the cane in late fall or early spring. However, due to the phase-out of diazinon in 2016, we can expect raspberry crown borer will be making a comeback. Growers will be using new methods to control this pest.
The first step in control is to recognize raspberry crown borer damage before it causes significant damage. In spring, watch for wilting or dying primocanes and areas of weak growth. By early summer, affected canes will pull out easily from the crown with a sharp tug. In late summer and early spring you might see canes with CN-tower shaped swellings near the base of the cane. But to accurately diagnose raspberry crown borer you need some gloves, a spade, and a pair of clippers. Dig up the crown, clip off the canes and cut through the crown to look for frass, larvae and tunnelling (Figure 2).
Figure 2 - RCB larva and frass in crown
In late summer, watch for RCB adults (Figure 3) and eggs (Figure 4) to help optimize control. Researchers have been unsuccessful in developing a stable pheromone for field use. However adult RCB are active on sunny days and can be found on foliage in August and September. Eggs are also visible on the underside of leaves. Figure 5 shows the raspberry crown borer life cycle, depicted in an Agriculture Canada Publication in the 1960''s.
Figure 3 - RCB adult
Figure 4 - RCB egg (photo by Carolyn Teasdale)
Figure 5 - RCB life cycle (photo by Agriculture Canada)
Altacor insecticide is registered for raspberry crown borer. This product will control hatching eggs and young larvae . Apply the first spray in late August or early September when eggs are hatching, ensuring good coverage of the whole plant. Follow this with a second application in early to mid- October, using a high volume spray which includes the base of the cane to target young larvae. Prune old canes close to the ground and control weeds in the row to help discourage further crown borer attack. In future, degree day models, pheromones, mating disruption, and biocontrols could be developed for crown borer management. However, this pest will likely make a resurgence before research dollars are directed towards improved control.
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|Creation Date:||01 November 2016|
|Last Reviewed:||01 November 2016|