Мучнистая роса винограда: возбудитель, симптомы и методы борьбы.

Species of fungus

Uncinula necator (syn. Erysiphe necator) is a fungus that causes powdery mildew of grape. It is a common pathogen of Vitis species, including the wine grape, Vitis vinifera. The fungus is believed to have originated in North America. European varieties of Vitis vinifera are more or less susceptible to this fungus. Uncinula necator infects all green tissue on the grapevine, including leaves and young berries. It can cause crop loss and poor wine quality if untreated. The sexual stage of this pathogen requires free moisture to release ascospores from its cleistothecia in the spring. However, free moisture is not needed for secondary spread via conidia; high atmospheric humidity is sufficient. Its anamorph is called Oidium tuckeri. It produces common odors such as 1 octen 3 one and (Z) 1,5 octadien 3 one. This mildew can be treated with sulfur or fungicides; however resistance to several chemical classes such as Benomyl, the DMIs, and Strobilurins has developed. While synthetic fungicides are often recommended as applications around bloom, it is common to include sulfur in a tank mix to help with resistance management.

Powdery mildews are generally host specific, and powdery mildew of grape is caused by a host specific pathogen named Uncinula necator. Powdery mildew is a polycylic disease that thrives in warm, moist environments. Its symptoms are widely recognizable and include gray white fungal growth on the surface of infected plants. A sulfur formulation, fungicides, and limiting the environmental factors that favor the growth of powdery mildews are all practices that can stall and/or halt its growth.

Powdery mildews are generally host specific. Uncinula necator is the pathogen that causes powdery mildew on grape. The most susceptible hosts of this pathogen are members of the genus Vitis. The signs of powdery mildews are widely recognizable and easily identifiable. The majority of them can be found on the upper sides of the leaves; however, it can also infect the bottom sides, buds, flowers, young fruit, and young stems. A gray white, dusty, fungal growth consisting of mycelia, conidia and conidiophores coat much of the infected plant. Chasmothecia, which are the overwintering structures, present themselves as tiny, spherical fruiting structures that go from white, to yellowish brown to black in color, and are about the size of the head of a pin. Symptoms that occur as a result of the infection include necrosis, stunting, leaf curling, and a decrease in quality of the fruit produced. Most infection begins when spring rain (2.5mm) falls and temperatures are approximately 15 °C or higher. Rates of infection decline at temperatures higher than 30 °C, since the evaporation of water occurs readily. Cooler conditions, such as shading and poor aeration, promote infection due to a higher relative humidity, optimally 85% or greater. However, sporulation does occur at levels as low as 40%. Spores are dispersed mostly by wind and rain splash. Young underdeveloped tissues are most susceptible to infection, primarily leaves and fruit. Warmer weather cultivars of Vitis vinifera and French hybrids provide overwintering protection in buds and during moderate winters climates. American cultivars are generally less susceptible to infection unless an unusually warm winter does not kill the chasmothecia in buds. Most chasmothecia survive on the vine where ample protection is provided in the bark.

First and foremost, limiting environmental factors that promote infection are key to managing powdery mildew on grapes. Optimal sites feature full sun on all grape structures and ample aeration to reduce humid microclimates under shading leaves. Pruning vines and clusters and planting on a gentle slope and orienting in rows running North and South promote full sun and aeration. Dusting leaves and berries with lime and sulfur was effective in the 1850s during the epidemic in Europe.