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Powdery mildew, caused by Uncinula necator (Schwein) Burrill is one of the most damaging disease affecting grapevines (Vitis vinifera L.) in Mendoza and worldwide, reducing yield and fruit quality. Throughout six growing seasons (2001/02; 2002/03; 2005/06; 2007/08; 2008/09; 2009/10), powdery mildew incidence values (expressed as daily epidemic increment rates) were observed in clusters from flowering to onset of ripening (change of color of the grape berries), in a grapevine planted with the susceptible Chenin cultivar at the EEA INTA Mendoza (Luján de Cuyo). From hourly values of thermal-moisture elements recorded by upper canopy sensors, meteorological variables were calculated in the 15 previous days of each epidemic observation. Using variables which integrate the effects of air temperature and humidity and frequency of light precipitations over the epidemic progress, logistic models were adjusted for estimating the probability of occurrrence of severe, moderate and nil epidemic increment rates, reaching maximum prediction accuracy of 92.5% (two variable models, N=40). Predicted values by the univariate model (selected by Stepwise procedure; prediction accuracy: 87.5%) were validated with the epidemic curve observed during 2000/2001 growing season. These model predictions could complement epidemic observations, giving regional scale to warning systems for improving the decision making process regarding disease chemical control. [ABSTRACT FROM AUTHOR]

The marigold (Calendula officinalis) is an herbaceous plant used by its beautiful yellow or orange flowers, in bordures, gardening and as cut flower. It is largely diffuse in the world, not only for the beauty of his flowers or his use in cosmetic, but for being resistant, of easy cultivation and for it low demanding in environmental conditions. In Mendoza it is very used as ornamental plant and every year is affected by a disease called powdery mildew. In Argentina there are mentioned as etiological agents of the disease different species of the generous Erysiphe, and Oidium erysiphoides. Nevertheless the teleomorphic form wasn't described until 1991 in Corrientes and Córdoba. There, it was reported as Sphaerotheca fusca. In 2004 in Mendoza, it was observed over marigold cultures a severe powdery mildew attack. Studying the problem, over the typical powder of the disease, the presence of black bodies was observed. This motivated to determine the etiology of the disease in Mendoza. Several samples of marigold plants affected were taken at different places. At the laboratory, morphological and morphometric studies permitted the identification of Podosphaera fusca (=Sphaerotheca fusca) as causal agent of the powdery mildew of the marigold in Mendoza. [ABSTRACT FROM AUTHOR]

Leveillula taurica (Lév.) Salm. is a pathogenic fungus, at the moment, in expansion in Argentina and particularly in Mendoza. Physalis viscosa (groundcherry) grows spontaneously in several cultures and in its surroundings in Argentina. The finding of L. taurica on camambú a wide spread specie in our country has motivated the present study. The symptoms were characterized by the presence of yellow cuneiform patches in the adaxial face of the leaves corresponding with a white plush on the other leave face. Etiological studies based on the histopa-thology of the diseased tissues and fungal morphology have confirmed the presence of Leveillula taurica (Lév.) Salm on it anamorphic face of Oidiopsis taurica Sal. [= Oidiopsis sicula (Scal)]. Since it was found for the first time in 1996 in Tupungato, the fungus has been spreading itself everywhere in Mendoza. The pathogen attacks camambú from Decem-ber to May. This lengthy attack period could represent and important source of inoculum for susceptible cultures. This paper is the first report of L. taurica on Physalis viscosa not only in Argentina but worldwide. [ABSTRACT FROM AUTHOR]