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ARS Home » Southeast Area » Poplarville, Mississippi » Southern Horticultural Research Unit » Research » Publications at this Location » Publication #256854
Title: Powdery Mildew of Dogwoods: Current Status and Future Prospects

Author
item LI, YONGHAO - University Of Tennessee
item MMBAGA, MARGARET - Tennessee State University
item WINDHAM, ALAN - University Of Tennessee
item WINDHAM, MARK - University Of Tennessee
item TRIGIANO, ROBERT - University Of Tennessee

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2009
Publication Date: 11/1/2009
Citation: Li, Y., Mmbaga, M.T., Windham, A.S., Windham, M.T., Trigiano, R.N. 2009. Powdery Mildew of Dogwoods: Current Status and Future Prospects. Plant Disease. http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-93-11-1084.

Interpretive Summary: Powdery mildew continues to be the greatest detriment to production of flowering dogwood in the United States and other countries. Fungicide programs, which are very effective in controlling the disease, require spray applications at regular intervals throughout the growing season. These applications add significantly to production costs that may be cost-prohibitive to many small- to mid-size nursery producers across the mid-south. In the deep-south, nurseries have ceased growing flowering dogwood for this reason. Biorational chemical candidates and perhaps even some biological control organisms hold some promise for managing the disease, but additional research is required before these strategies will be viable options. Unfortunately, these approaches suffer from some of the same constraints as fungicide applications, in that they may require repeated and expensive applications of materials over the entire growing season. Natural resistance to powdery mildew has been documented in flowering dogwood, and this strategy appears to be the most cost effective way for managing powdery mildew in nurseries and landscapes. Breeding and developing new cultivars for powdery mildew resistance is somewhat problematic. Besides the long generation time, about 7 years, incompatibility between the F1 generation and either parent occurs as well as inbreeding depression; almost all BC1 generation plants are weak and have failed to grow and flourish. Our group will continue to select and research alternative breeding methods that are intended to introduce new cultivars of flowering dogwood that have resistance to powdery mildew.

Technical Abstract: For many years, nurseries that produced flowering and kousa dogwoods had the luxury of working with relatively diseasefree crops. Disease management and control costs were minimal and estimated at approximately $120/ha/year. In the late 1970s, flowering and kousa dogwoods were threatened by a new disease, dogwood anthracnose, caused by Discula destructiva, which was reviewed by Daughtrey et al. In 1994, another disease, powdery mildew, reached epiphytotic levels in flowering dogwoods. Tens of millions of dollar’s worth of dogwoods were destroyed and millions of cultivated seedlings lost their commercial value because formal management strategies were not formulated. In subsequent years, fungicide management costs were estimated to be $1,975/ha/year. Many small producers of dogwoods terminated production of the tree because they could not afford the additional overhead or were not inclined to continue routine fungicide sprays every 2 weeks from May to October.