Plant Doctor Archive

Borer in wisteria

MY 12-year-old wisteria has a bad infestation of borer - it's even right down at the base of the plant. Can it be saved?

IT MAY survive. Often by the time you discover a borer attack the larvae has done its damage, pupated and flown off. Just in case the borer is still in the wisteria, you could try injecting something into the holes in an attempt to kill it off. Various products are reported to work, such as petrol, kerosene and a range of insecticides. The difficulty is in getting the product into the small holes and far enough into the tunnels to affect the larvae.

You could try No Borer Spray Injector Aerosol which is available from most hardware stores. It is mainly intended for use on furniture, but is also listed as effective for lemon tree borer in plants. However, if that doesn't work, there's still hope as wisterias are notoriously hard to kill. Even if all the top growth dies off there's a good chance you'll get new shoots coming from below the damaged area next spring, possibly even from below the soil level.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.