Growers of Coleus should be on the look out for a new strain of Downy Mildew specific to Coleus and Basil (Ocimum). The symptoms include leaf spotting, twisting and leaf drop. The sporulation on the underside of the leaves is sometimes visible as the spores darken. Early detection is difficult and the disease can become widespread under humid conditions because the symptoms are hidden on the underside of the leaves. There are no other known hosts to this strain of Downy Mildew at the moment. Growers that encounter the disease should take a number of preventative measures. Avoid keeping stock over to the next season because the disease can overwinter on stock plants even on plants that appear healthy. Avoid replanting with other members of the Labiateae family. Keep Coleus plants grown from seed separate from vegetatitive cuttings brought onto the nursery. Cuttings received from external sources can be a primary means of introducing the disease. As protection, plants can be treated with an appropriate systemic or partially systemic fungicide. Margery Daughtrey Extension Service Cornell University www.hort.cornell.edu/greenhouse
In Piemonte, Italy, the presence of a type of Oidium (in reality Podosphaera o Sphaerotheca spiraeae Sawada) was seen for the first time in 2005 on plants of Spiraea x vanhouttei and Spiraea cinerea. Gilardi G., Minerdi D., Garibaldi A. (2006) “Sensibilità di spirea al mal bianco da Podosphaera (Sphaerotheca) spiraeae Sawada”. Informatore Fitopatologico. LVI(5): 54-57 mirtserv@fondazioneminoprio.it |
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