Rose Stem Girdler (Agrilus cuprescens)
- Red raspberry
- Black raspberry
- Wild and cultivated roses
The rose stem girlder is a small flat-headed, metallic beetle that is a common cane-boring pest of raspberry, blackberry, and wild rose in central and northern regions of the state. Larvae tunnel in the canes causing gall-like swellings and cane breakage. The rose stem girdler can dramatically reduce stands of raspberry canes, and even kill out a planting.
Adults are slender, flattened, metallic beetles slightly less than 1/4 inch long with copper-colored wing covers. Males have a metallic green "face."
Eggs are 1/16 inch, round and flattened. They're laid singly on canes and cemented in place with a viscous substance that turns yellow and becomes brittle, giving the appearance of an insect scale.
Larva are 1/4 to 3/8 inch long, milky white with the first segment behind the head slightly yellow and mouthparts brown to black.
Pupa are slightly less than 1/4 inch long, shiny white, and turning light brown with age.
- Ragged edges on leaves from adults chewing on the edges.
- Wilting and dead canes from larval tunneling and feeding.
- Gall-like swelling.
Good cultural practices, such as proper fertility and irrigation management are critical to growth of healthy, non-stressed brambles. Healthy plants are in turn less susceptible to attack by pests.
Sanitation and Pruning: Avoid planting raspberry and blackberry stands near roses, or remove nearby roses before planting brambles. Wild and shrub-like roses are particularly attractive hosts, and can increase the population of rose stem girdler in the nearby vicinity.
Prune out and destroy infested canes in spring through summer to remove larvae. Prune below the point of insect boring activity, or remove entire canes. Secondyear canes generally wilt before harvest and should be removed at that time. Infested canes should be destroyed by burning, composting, or burying in soil at least 2 inches deep to prevent adults from emerging. If an infestation is substantial, pruning should be supplemented with chemical control.
Insecticides: Insecticide applications are ineffective against larvae because the chemicals cannot reach them inside the canes. Applications should be timed with adult emergence in an attempt to prevent egg deposition on canes. Begin applications in early May, or just before bloom, and repeat based on the reapplication interval of the product through early June. If applications are made during bloom, wait until nearly dusk when bee activity has ceased for the day. Materials should be applied as full cover sprays to entire canes. Always read and follow all product label directions. Strictly follow all bee protection guidelines. Note and follow the required time interval to re-enter the site after application (re-entry interval) and wait-time until harvest of fruit (pre-harvest interval).