I have had problems with rose borers in the past. I am planning on purchasing new shrub roses and want to avoid this problem.
Healthy plants are your best defense against borers and other insects. Pith borers burrow into rose canes through pruning cuts. Many rosarians place a drop of white glue on cut canes. This seems to eliminate the problem. Stem girdling borers are more troublesome. Prune out older canes (3 years and older) on suckering type roses. The younger canes are less susceptible to borers so regular pruning helps minimize borer problems.
Photo: James Solomon, USDA Forest Service