Question
My sisters lilac bush is dying one branch at a time. No bugs or mites. The leaves on a branch just turn crispy brown and our dead. Nothing is chewing them that I can see. We live in eastern Iowa. Thanks for your time.

J.D. Koppenhaver

Answer
Hi. If your problem is not stress related, IE: water or heat than it sounds like Lilac Borers. Examine the canes and the base of your lilac for the signs listed below.

Description:  Canes or stems wilt suddenly. The base of infested stems are swollen and the bark separates from the wood. A fine sawdust-like material is present around holes in the canes.
Lilac borers overwinter as larvae in infested trees and shrubs. Pupation occurs in the spring. Moth emergence generally begins in mid- to late-April, peaks in May, dwindles by mid- to late-June and ends by the first week of July. The moth has clear wings and resembles a wasp in appearance. It is about 1" long and has a wing span of about 1?inches. Moths deposit eggs in cracks and crevices of bark. They hatch in 10 to 14 days. Larvae immediately bore into wood. Frass accumulates around holes. Swelling and cracking of the bark are associated with repeated infestations and branches may be severely weakened at the feeding sites. During dry periods in late summer, terminal shoots of infested plants wilt. There is one generation per year.

Recommendations: Treatment Options
The insecticide product available for home use is Bayer Advanced Garden?Tree and Shrub Insect Control.
For additional treatment options, contact a local professional arborist.
Caution: read all label instructions before using any pesticide, avoid skin
contact, and store pesticides  where children cannot reach them.
Hope this helps,Bill