Pesticidi i Fitomedicina (Jan 2007)
Uncinula necator (Schow) Burr., the Causal Agent of Grape Powdery Mildew: Economic Impact, Epidemiology and Control
Abstract
The article is an overview of what we know at present about the patogen Uncinula necator and the disease powdery mildew of grapevine, i.e. its economic status, inoculum source, microclimate conditions, vine susceptibility and principles of its protection.Powdery mildew is a major grapevine disease in terms of losses. It infects the plant’s green parts, reducing its fertility, spoiling the quality of grapes and wine and ruining plant vitality. The process additionally affects subsequent vegetation seasons. The disease occursevery year and its intensity depends on a number of factors.It had long been assumed that overwintering mycelium was the primary source of inoculum. More recent research, however, has revealed a crucial role of cleistothecia in many vineyards. They were found in our vine-growing regions long ago but their true role in the epidemiology of disease has been explained only recently.Microclimate conditions considerably affect the abundance and vitality of cleistothecia and the pathogen’s infection potential. Outbreaks and intensity of disease both depend on them, while vine susceptibility plays another important role, depending on cultivarand plant ontogenesis. Grapevine is most sensitive during flowering and bunch formation when conditions are generally good for the disease to appear and spread.Temperature, precipitation and relative air humidity may limit the occurrence of powdery mildew, but extreme values in that respect are a rarity. Their normal scope is more or less favourable for the disease, especially in Podgorica vineyards.Knowing the pathogen, especially its infection potential, environmental conditions, dynamics of host development and timely and good quality protection of vines, both preventive and chemical, is crucial for grapevine protection.Prevention is important but treatments with fungicides are crucial for U. necator control, and they can either focus on destroying the inoculum and delaying mildew outbreaks or on preventing primary and secondary infection and spreading of disease. Fungicides that arenormally used include some old compounds (sulphur, dinocap) as well as new ones (strobilurins and hinolines), while inhibitors of ergoserol biosynthesis have an increasing role.
