Needle Blight on Leyland Cypress

This has been a particularly bad year across the Southeast for Cercospora needle blight on Leyland Cypress. This may be due in part to cooler night temperatures occurring earlier than normal.

The symptoms of Cercospora needle blight show up first on the interior, lower branches of the tree and move upward and outward. The needles turn brown and small brown lesions can be seen on the twigs. Defoliation follows. Using a hand lens, you can see masses of spores produced by the fungus which appear as olive-green to grayish feathery tufts on the blighted needles or small twigs.

This fungus is not active until about mid June, peaking in August and September, and remains active until about the end of October. Fungicide applications can start about July 1 and continue until the end of October after the disease has been accurately diagnosed. (Do not get this disease confused with the other things that plaque leylands like algae growth, bagworms, cankers, etc.) This is an expensive regime, but is effective. A fungicide rotation is recommended and probably best done by a professional since leylands tend to be tall and hard for homeowners to reach with fungicides. Some fungicides recommended are Quadris (azoxystrobin), Daconil (chlorothalonil), Bravo (chlorothalonil), Fore (mancozeb) or Kocide (copper hydroxide). Most of these a homeowner can purchase but come in such a large quantity and therefore expensive makes it worth contacting a professional for fungicide treatments. It is important to follow to retreat at the recommended intervals. Treating once per month, for instance, is not going to be as effective as you will be allowing new infections to start. If you haven't starting making any fungicide applications yet, it is not too late to combat this disease (it will just take longer to get the problem under control).

Fore, Daconil, and Kocide when applied at 7-day intervals have all worked very well in reducing disease (starting about July 1 and continuing until the end of October). It is critical that the needles in the inside of the tree are saturated with fungicide. Air blast sprayers have not been getting good control as they do not seem to get enough fungicide into the center of the tree (which is where infection starts).

Damaged trees generally flush out again in about 2 months time if they are not too severely damaged. Therefore, BE PATIENT. Keep in mind that there is a lot of sporulation going on right now, but symptoms may not have developed yet. As such, even though you are spraying fungicides you will continue to see symptoms develop from the earlier infections. Again, BE PATIENT as you should eventually see a turnaround.

This disease has never be observed to kill a tree, but it can disfigure a tree enough to make it unmarketable if the disease is severe. So it is very important for nursery growers to scout and treat for this disease.

Pruning greatly increases disease incidence and severity. Trees in nurseries as well as landscapes that have not been pruned do not tend to have the disease or as severe. There is something about opening up the interior of the tree that promotes disease development, which is different from most other foliar diseases in which opening up the canopy actually reduces disease severity.

For help with your leyland cypress or any gardening question please call the Wilson County Master Gardeners at 237-0113 or email at wilsonmastergardener@hotmail.com.

Any reference to trade names is made with the understanding that no discrimination is intended and no endorsement by the North Carolina Cooperative Extension Service is implied. Use pesticides safely. Read and follow all label directions. Information in this article is based on studies researched by Dr. Jean Williams-Woodward in Georgia for the past 3 to 4 years.

Date Created: 12/10/2004.