Diseases
It is important to properly sanitize any components of the production system such as irrigation lines and tubes, weed mats or containers that are re-used the following year.
The most common disease problems found on garden mums are the root rots caused by Pythium and Rhizoctonia, bacterial leaf spot and the leaf spots caused by Alternaria, Botrytis and Septoria. In contaminated root media or field soil, Fusarium wilt may also develop. Symptoms include one-sided yellowing and wilting of branches. Severe infections can destroy plants. Root rots are best prevented with the use of well-drained root media. Chemical controls typically involve the use of Banrot, Heritage, Subdue MAXX or Subdue MAXX/Medallion or Truban drenches.
The best control for Fusarium wilt centers on disease-free cuttings and pathogen-free gowing media. Heritage and Medallion have been reported to provide good Fusarium suppression. Alternaria, Botrytis and Septoria can normally be controlled with chemicals such as Heritage, Chipco 26019, Compass, Daconil Ultrex or Medallion used as preventative sprays. As garden mums grow rapidly in August and develop a dense canopy of leaves, these sprays may be beneficial.
Black lesions on the foliage characterize bacterial leaf spot, caused by Pseudomonas cichorii. The entire leaf may seem healthy except for the black lesion. This bacterial disease must have free moisture on the leaf surface in order to develop. Overhead irrigation late in the day and/or daily rains during warm weather can lead to its development and rapid spread.
There is no chemical control for bacterial leaf spot. Copper compounds, such as Camelot, Copper-Count-N, Kocide and Phyton 27 have shown prevention potential in our trials but they can also be phytotoxic if applied too often and bacteria may become resistant with repeated use. Some pathologists have recommended a preventative spray of ½ pound Kocide and 1½ pounds Manzate per 100 gallons when rainy conditions prevail. However, this leaves an unsightly residue and prevention has not been well documented. Cultural practices such as good air circulation, proper spacing and avoiding overhead watering are the best prevention for bacterial leaf spot.
For additional information on chrysanthemum disease control, refer to Yoder’s Tips on Chrysanthemum Disease Control. If sending problem samples, send both good and bad plants for comparison.
Insects and Diseases
Disease Control (version 07260)Pest Control (version 07261)Chrysanthemum Stunt Bulletin (version 07216)Chrysanthemum White Rust Bulletin (version 07228)
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