Borers typically infest weakened trees. They rarely infest healthy trees. Drought, disease, pests, root damage during construction, or over-pruning first injures the trees. Borers are then attracted to the trees in the weakened condition. Simply controlling borers chemically will not make the trees healthier.

Sometimes borers can be controlled chemically while the real cause for the decline is treated. This strategy has helped some trees recover from decline, but the recovery can take many years.