Passalora Needle Blight Of Leyland Cypress

Disease Information

Passalora Needle Blight

Symptoms and damage

Although often referred to as Cercospora or Cercosporidium needle blight, this disease is caused by the fungusPassalorasequoiae (previously known as Cercosporidiumsequoiae, Asperisporiumsequoiae and Cercosporasequoiae).Typically, this disease only affects plant growth that is at least one year old. Symptoms usually appear during summer months. They include browning of needles and eventual needle drop. These symptoms start on lower branches near the trunk and then spread outward toward branch tips. Over time, the disease moves up the tree. The portion of a tree displaying symptoms may increase from one year to the next until only the tips of upper branches are still green or the tree dies completely. The disease will sometimes be more prevalent on one side of the tree then the other, especially when irrigation spray is a contributing factor. When irrigation spray is not an issue, it is more likely to be seen on the north and west sides of trees where the morning sun is not able to dry branches as quickly. In cases of severe disease, all needles (except current year`s growth) turn brown, resulting in green needles being present only on branch tips. Spores develop during late spring to summer. They are spread primarily by rain, overhead irrigation, and wind, but also by tools. Passalora needle blight symptoms somewhat resemble symptoms seen in a Leyland cypress that is responding to severe environmental stress, such as drought, in which its lower, interior needles turn yellow and drop.

Management

When planting, space trees to allow adequate air flow. To minimize spread of spores, avoid overhead irrigation or restrict it to early morning hours. Preferably, use drip irrigation and make sure that enough water is being applied during drought situations. Drip irrigation hoses should be no more than 75 feet long as pressure drops significantly after that point. Prune out diseased limbs, disinfecting pruning tools between cuts using 10 percent bleach solution (1 part chlorine bleach to 9 parts water). Note: Be sure to clean and oil pruning tools after this procedure to prevent rust formation.

Fungicides such as thiophanate-methyl and myclobutanilare recommended for use against needle blight. However, to be effective, these sprays need to begin in late spring and continue through summer until the cooler, less humid months of fall. In addition, when applying these materials, it is essential that needles, including those on the inside near the trunk, are thoroughly sprayed to run-off. Once a tree is tall, adequate coverage by a homeowner is generally not feasible.

 



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