I have two very mature (18 yrs) purple plum bushes and just discovered they have bores. I have applied a product called annual tree insect control to base. Is there anything else I can do to try to save these bushes? One has already had (a leg?) of it die, which is what got me looking for problem.

HI Debra, It is fairly common to have borers in plum bushes especially in older branches. I'm not sure exactly what spray you used but I imagine it is one of the systemics. It can be good for some borers but is most effective if used early in the season. to control borers pesticide timing is very important. Generally for the borers that attack plums we would spray the trunk and lower limbs mid-June, again mid July and mid August with Sevin (carbaryl) or permethrin. Be sure to read and follow all label directions. I would prune out any dead branches and remove older branches if possible. check out this website http://www.urbanext.uiuc.edu/bugreview/peachtreeborer.html good luck, Sandy