How to Manage Pests
UC Pest Management Guidelines
Raspberry Crown Borer
Scientific Name: Pennisetia marginata
(Reviewed 12/09, updated 12/09, pesticides updated 6/15)
In this Guideline:
Description of the Pest
Although the adult raspberry borer is a moth, it resembles a yellowjacket wasp. Belonging to the family of clearwing moths, it has a wingspan of about 1 inch and has a black body with four yellow horizontal stripes on the abdomen as well as stripes on the thorax. The legs are yellow, and the feathery antennae, unlike the short antennae of a yellowjacket wasp, curve outward from the head.
The raspberry crown borer takes 2 years to complete its life cycle. The female raspberry crown borer moth lays up to 140 reddish brown eggs most often on the underside edges of caneberry leaflets in late summer. Once hatched, larvae migrate to the base of the caneberry plant where they either dig into the base of cane and form a blisterlike hibernaculum or find a protected area in the bark and stay there for the winter. With the onset of spring the following year, the larva begins to burrow galleries through the crown of the plant and continues to do so through the first summer. The second winter is spent in the roots; the larva is about 0.4 to 0.9 inches (1.3–2 cm) long at this time. The second summer, the excavation continues in the roots and crown. At midsummer of the second year, the larva is full-grown, measuring 1 to 1.5 inches (2.5–3.3 cm) long. It undergoes a short pupation period of 2 to 3 weeks in the burrow in the crown and emerges as an adult moth. Adult moths are active from early August to late September and may be seen during the day resting on foliage.
A caneberry plant that is infested with a raspberry crown borer larva will begin to wither and visibly wilt because of the physical damage to vascular tissue, especially in the second year of infestation. A hole at the base of the plant in the crown with sawdustlike frass at the entrance is also indicative of raspberry crown borer activity.
The best way to manage the raspberry crown borer is to prevent its intrusion into the caneberry field through the cultural controls. In the event that this pest establishes itself in the field, the chemical controls below may prove useful.
There is no commercially acceptable biological control for raspberry crown borer in the field at this time.
The use of clean planting stock is necessary to reduce the movement of infested plant stock from one field to another. The removal of wild blackberries surrounding the field can help reduce populations of raspberry crown borer.
Organically Acceptable Methods
Cultural controls are organically acceptable.
Monitoring and Treatment Decisions
Monitoring this pest is difficult because it is hidden away in the crown of the plant. By the time the damage is noticed, it is too late to do anything effective. If a population becomes established in the planting, treatments may be warranted.
UC IPM Pest Management Guidelines: Caneberries
Insects and Mites
M. P. Bolda, UC Cooperative Extension, Santa Cruz County
Acknowledgment for contributions to Insects and Mites:E. Show, Driscoll Strawberry Associates Inc., Watsonville, CA
E. J. Perry, UC Cooperative Extension, Stanislaus County