Focus on Floriculture Vol 3 #4
Verticillium wilt of chrysanthemum is caused by the soil borne fungus Verticillium albo-atrum. The disease symptoms are usually not seen in early stages of plant growth, but occur at the time the flower buds are first seen. Infected plants tend to wilt during warm periods of the day while healthy plants do not. The lower leaves yellow first and the yellowing, followed by death and drying of the leaves, progresses up the stem. These symptoms commonly develop at first on only one side of the plant and only after blossom buds have formed. Infected plants may be stunted and the flowers reduced in size. In severe cases, the petals turn brown and die. The most common methods of controlling Verticillium wilt is by placing disease-free cuttings in treated soil. Heating the soil to 140-160°F for 30 minutes with steam or steam-air is the most satis factory soil treatment. Of the chemical fumigants available, chloropicrin or chloropicrin-methyl bromide combination adequately controls the fungus. If other diseases are not a problem, benomyl has been used to control Verticillium wilt by dipping plants prior to planting or spraying plants within a week after transplanting. Unfortunately very high rates of benomyl (4-6 pounds of 50 WP Benlate) are required for effective control. These rates are not yet listed on product labels and therefore cannot be used.
Keywords: soil borne fungus chloropicrin steamed Chloropicrin or steam treated soil disease-free cuttings