Phytoparasitica (2002) 30 (3) - Overwintering of Uncinula ...

S. Ovadia, D. Shtienberg, A. Dinoor and A. Sztejnberg (2002)
Overwintering of Uncinula necator and the initial stages of grape powdery mildew development in Israel
Phytoparasitica 30 (3)
The 23rd Congress of the Israeli Phytopathological Society - February 11-12, 2002
Abstract: Unicula necator, the causal agent of powdery mildew, is the most devastating foliar pathogen of grapevines in Israel. The pathogen infects all the green parts of the plants but most of the damage results from bunch infections. Final disease severity and the resultant losses are influenced by the time of disease onset and by the spatial development of the disease at the beginning of the epidemic. U. necator may overwinter as mycelia in dormant buds, and in the form of cleistothecia that survive the winter and mature in the following spring. When infected buds flourish, the growing branch and the newly developed leaves are covered with U. necator mycelia and conidia. The diseased branches (flag-shoots) are assumed to be the only source of initial inoculum in Israel. In a study that was conducted in the years 1998 to 2001, the appearance of flag-shoots over time and space, and their role in disease development at the initial stages of the epidemic, were studied. Flag-shoots were found only in orchards of the cultivar 'Carignan' but not in 'Cabernet Sauvignon', 'Chardonnay' or 'Merlot'. The number of flag-shoots varied from vineyard to vineyard, but never exceeded 350 per ha. In the years 1998 to 2000, disease development in time and space was related to the appearance of flag-shoots: infections on leaves were observed only after the emergence of flag-shoots, and were located only in close vicinity to flag-shoots. In these years, disease onset was relatively late and the severities of the epidemics were mild to moderate. In 2001, on the other hand, the disease appeared earlier and its spatial distribution was not restricted to the location of the flag-shoots. This may suggest that ascospores, produced in over-wintering cleistothecia, served as another source of initial inoculum in 2001.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Dani Shtienberg

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Erysiphe necator	Grapevine (Vitis)	Israel