WSU Whatcom County Extension

Integrated Pest Management for Raspberries

Raspberry Beetle

(Byturus unicolor)

Insects and Invertebrates

 

Raspberry Beetle Feeding

 

Symptoms

When the adults emerge from the soil in mid spring, the raspberry beetle will feed on new leaves in an interveinal pattern. Primocane leaves close to the ground are usually eaten first, but damage can be seen on leaves into the canopy.  Adults are then attracted to flower buds where mating occurs; some feeding may occur on unopened flower buds.  This pest is a harvest contaminant; larvae may be present in the receptacle of the fruit and drop off during machine harvest.  Larvae do not often fall off into the fruit when harvested by hand.

 

Raspberry Beetle

 

Identification

The adult raspberry beetle is between 0.15 and 0.2” in length, a reddish brown color with short hairs covering its whole body. The larvae are between 0.1” and 0.25” in length depending on the time of season. They are a light cream color with darker bands across its body.

 

Raspberry Beetle Damage

 

Life History

Overwintering in the soil, the adult emerges in the spring between mid-April and mid-May depending on soil temperatures. The adults feed on leaves, often on the new primocane leaves, but in areas of high populations they will also feed on upper floricane leaves. Adults are then attracted to flower buds and blooms where mating and, subsequently, ovipositing occurs.  Larvae (or fruitworm) emerge from the eggs on the flower or immature fruit and begin feeding on the receptacle. The larvae will remain in the receptacle until the fruit is harvested or falls to the ground at fruit maturity in late summer. Pupae are present in the soil in late summer to early autumn. Adult beetles emerge from the pupae in late autumn and remain in the soil until the spring.

 

Raspberry Beetle Trap

 

Monitoring

Monitoring can be done in four ways: looking for leaf damage, using Rebell® Bianco sticky traps, beating trays or monitoring fruit infestation.

In mid-spring, the raspberry beetle will feed on new leaves in an interveinal pattern. The amount of leaf damage may be related to the population of raspberry beetle in your field. The timing of adult emergence from the soil appears to depend on soil temperatures with emergence dates ranging from mid-April to mid-May in Whatcom County. Scout 3-5 sites per field, (depending on field size) and evaluate 10-20 hills, spaced 3-5 hills apart on both sides of the aisle way. Look for incidence of raspberry beetle feeding and rate on a scale of 0-3.

The Rebell® Bianco sticky trap can also be used to assist in scouting for the raspberry beetle. By early April, place traps every 20-40 rows around the perimeter of the field; attach the trap to the top wire, approximately one post in from the edge of the field.  Monitor traps once per week, or at least once before deciding on treatment for raspberry beetle.  Record the date and number of beetles trapped at each site.

Take beating tray samples at each scouting site to monitor for raspberry beetles that are feeding on leaves in the canopy.  They are most active on warmer days.

During harvest, monitor for infested fruit and train harvest workers to look for larvae in the fruit.  High levels of infestation can be an indication that a treatment will be necessary in the following year.

 

Thresholds and Management

Beating tray threshold depends on processing type; check with your processor to determine your threshold.  Counts of 1-2 beetles/10 trays have been recorded with no reported damage to fruit.

Thresholds for beetles trapped in the Rebell® Bianco trap depend on processing type; IQF and high end fruit will have a lower threshold. Average the total number of beetles trapped over the number of traps in the field.

You may want to apply a pesticide treatment for raspberry beetle if the average trapped beetle count is:
For:
Above 2 beetles per trap on average
Machine harvested IQF berries
Above 5 beetles per trap on average
Machine harvested fruit going to straight pack, juice, puree
Above 15 beetles per trap on average
Hand harvested fruit

 

Resources

WSU Whatcom County Extension, Integrated Pest Management for Raspberry Beetle
http://whatcom.wsu.edu/ag/IPM/raspberry_beetle_fact.pdf

Ohio State University, Brambles – Production Management and Marketing: Chapter 4, Insects & Mites
http://ohioline.osu.edu/b782/b782_21.html

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WSU Whatcom County Extension 1000 N. Forest St., Suite 201, Bellingham, WA 98225 (360) 778-5800 whatcom@wsu.edu