Efficacy of Fungicides for the Control of Myrothecium roridum on Dieffenbachia picta ‘Compacta’

Robert T. McMillan


Myrothecium leaf spot, caused by the fungus Myrothecium roridum, is a serious disease of Dieffenbachia picta Schott cv. Compacta. In 2009, six products were trialed for efficacy against M. roridum in a shade house. The D. picta plants were started from tissue-cultured liners potted in 6-inch plastic pots. ‘Compacta’ liners were potted for each of the six treatments including an untreated control. Natural infection was allowed to take place prior to the first application of the chemicals. Fungicides were applied on a 7- to 21-d schedule or on a closer interval depending on disease severity and replicated 4 times per treatment. Chipco 26019 (iprodione) at 2 lb per 100 gal of water, Compass O (trifloxystrobin) at 1 oz per 100 gal of water, Daconil 2787 (chlorothalonil) at 1.5 lb per 100 gal of water, Heritage (azoxystrobin) at 4 oz per 100 gal of water, Medallion (fludioxonil) at 2 oz per 100 gal of water, and Systhane (myclobutanil) at 2 oz per 100 gal of water were significantly more effective in the control of Myrothecium leaf spot than copper at 1.5 lb per 100 gal of water.


Dieffenbachia picta cv. Compacta, Myrothecium roridum, leaf spot

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283