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grapevinetrunkdiseases - 1 JANUARY/FEBRUARY 2005...

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JANUARY/FEBRUARY 2005 BY W. D. Gubler, P. E. Rolshausen, F. P. Trouillase, J. R. Urbez, T. Voegel Dept. of Plant Pathology, University of California, Davis, CA G. M. Leavitt, University of California Cooperative Extension, Madera, CA E. A. Weber, University of California Cooperative Extension, Napa, CA G rapevine trunk diseases are responsible for significant eco- nomic losses to the wine industry worldwide. Symptoms of these diseases include dead spurs, arms, and cordons and eventual vine death due to canker formation in the vascular tis- sue. In Eutypa dieback, deformed leaves and shoots occur as the pathogen invades spur positions. As cankers develop, yield reductions occur due to the loss of productive wood. The impact of grapevine wood diseases can be significant in older vineyards, and usually becomes more severe as vineyards become older. Eutypa dieback, caused by Eutypa lata was originally thought to be responsible for most canker development in California vineyards. However, recent findings have highlighted the importance of other fungi involved in the death and decline of grapevines in California. In this regard, Botryosphaeria species have also been recovered from cankers, and were determined to be the main cause of canker diseases in some California vineyards. Recent research has also indicated the occurrence of several new fungal trunk disease pathogens of grapevine belong- ing to the family Diatrypaceae (the same family as Eutypa ). These include Eutypa leptoplaca, Cryptovalsa ampelina , Diatrype species, and Diatrypella species. We will present current information on the epi- demiology and control strategies of fun- gal organisms responsible for grapevine spur, cordon, and trunk dieback in California. 1 G R A P E G R O W I N G RESEARCH UPD A TE Grapevine trunk diseases in California Figure I: Fruiting bodies (perithecia) of E. lata on a grapevine previously grafted for variety change. The large pruning wound favored formation of E. lata perithecia on the dead trunk of the old variety. Figure II: Black stroma bearing perithecia (fruiting bodies) of E. leptoplaca on dead trunk of big leaf maple collected in St. Helena, Napa County, CA.
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JANUARY/FEBRUARY 2005 Eutypa dieback Eutypa dieback was responsible for a loss in net income for California wine grapes estimated to be over $260 mil- lion in 1999. Many growers consider Eutypa to be the most significant dis- ease of grapevines. Typical symptoms of E. lata include formation of a wedge-shaped canker and stunted shoots with cupped, tat- tered, chlorotic, and necrotic leaves that are best seen in spring time. Foliar symptoms are due to toxins produced by E. lata. Differences in susceptibility of grapevine cultivars to infection have been reported, although no cultivars are immune. Cankers develop down- ward at a faster rate than toward the end of cordons and also increase in diameter over time. Extended infection of grapevines by E. lata leads to vine death.
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