Erysiphe necator

Genus/species (aliases): Erysiphe necator (Uncinula necator)

Classification: Ascomycete

Morphology: 
  • Cell: Ovoid
  • Colony: Overlapping white threads
  • Spore: Grape berry shaped with attached conidiophore
  • Zygote: Small sacs that give rise to asci
  • Ascus: Long sacs housed in spherical Cleistothecia
  • Liquid Growth: Clumpy

Physiological Traits: Uses leaves and berries as growth substrates.


Ecological Traits: found only on grapevine (Vitis) species.


Distinguishing Features:

Superficially, the fungus creates white, powdery like spots on the top side of the leaves, and on the berries. Erysiphe necatoralso has reddish-black resting structures, known as cheisthothecia.


Role in wine:

Powdery mildew is a major grapevine pest, and when infested berries are processed, it can result in off flavors in wine. Also, sulfur widely used for control of this grape pathogen has been associated with hydrogen sulfide formation in wine.


Sensitivities:

  • SO2: Affects germination @ 571 μg/m3
  • Sorbate: N/A
  • DMDC: N/A
  • pH: >8.0
  • Acids: N/A
  • Ethanol: N/A
  • Anaerobiosis: N/A
  • Heat: metabolism stops >32C

References:

  • Jackson, R.S. 2008. Wine science. Principles and Applications. San Diego, Calif: Academic Press Inc. 187-189.
  • Pscheidt, J.W. 2009. An Online Guide to Plant Disease Control. Oregon State University Extension. http://ipmnet.org/plant-disease/disease.cfm?RecordID=525.
  • Rumbolz, J. et al. 1999. Differentiation of infection structures of the powdery mildew fungus Uncinula necator and adhesion to the host cuticle. Canadian Journal of Botany. 78: 409-421.
  • Gubler, W.D. and D.J. Hirschfelt. 1992. Powdery Mildew. In: Grape Pest Management. Univ. of California Agricultural and Natural Resources Publications. 3343: 57-63.
  • Kassemeyer, H.H. and B. Berkelmann-Lohnertz. 2009. Fungi of Grapes. In: Biology of Microorganisms on Grapes, in Must, and in Wine. H, Konig et al. eds. 61-87.