September 14, 2013

1 - Drought and other environmental stresses have led to diseases in junipers as the monsoon rains brought increased moisture and humidity.

Yard and Garden September 14, 2013

Last week's Yard and Garden column about the insect problems that are appearing this year due to the very dry conditions we experienced in New Mexico until this year's monsoon developed only addressed a part of the problem. Cheryl Kent, Bernalillo County Extension Horticulture Agent, told me that she has been finding cases of fungal disease in many junipers. This disease, Phomopsis blight, develops most readily in injured plants when the humidity is high. Dr. Natalie Goldberg, NMSU Extension Plant Pathologist, has written a fact sheet on Phomopsis blight. It is available at the Plant Clinic and has provided the information for this article. There are other potential plant diseases, but this one is being observed in New Mexico this year. Newly planted juniper plants and containerized nursery plant are most often affected, but mature landscape plants may also show the effects of this disease. According to the fact sheet, the symptoms first appear as development of pale green to yellow color of the new foliage which ultimately dies. The color of the foliage becomes reddish brown as the disease progresses. The infected tissues produce large quantities of fungal spores that spread the disease under proper environmental conditions. The increased humidity and moisture that much of New Mexico has experienced this summer has provided the proper environment for development and spread of Phomopsis blight. Dr. Goldberg's fact sheet provides some cultural practices to minimize the impact of Phomopsis blight. The first and most effective way to minimize fungal damage is to plant resistant varieties. However, other recommendations are proper plants spacing to allow good air circulation, planting in well-drained soil in sunny locations, summer pruning during dry times, irrigation early in the day avoiding wetting the foliage, proper fertilization that does not stimulate excess growth, and removal and disposal of infected branches and plants. This article summarizes the information in the Phomopsis Blight Fact Sheet. For more information, you can get a copy of the fact sheet from your local NMSU Cooperative Extension office or from the Plant Clinic.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


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