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Tuesday, April 1, 2014

Fungal Diseases of Grapevines: Overview

There are so many things to remember about fungal diseases of grapevines so I put it all together in a table so that I could compare the details side by side.
Downy Mildew Powdery Mildew Black Rot Phomopsis
Latin Name Plasmopara viticola Erysiphe necator Guignardia bidwellii Phomopsis
viticola
Lifecycle Downy Mildew Lifecycle Powdery Mildew Lifecycle Black Rot Lifecycle Phomopsis and
Leaf Spot
Lifecycle
Primary Infection Oospores Ascospores Ascospores Pycnidiospores
Secondary Infection Zoospores Conidia Pycnidia
Overwintering Form Oospores in fallen leaves
Mycelium in buds
Hyphae inside dormant bud scales
Cleistothecia on the surface of the vine
Mummies in berries, vine or in the ground Mycelium and pycnidia in bark
Mycelium in dormant buds
Favorable Conditions Warm and wet conditions
Infection generally occurs in the morning
High humitiy, temperatures between 68 to 81 oF
Low, diffuse light
Shady portions of the vineyard
Temperature and age of tissue when infected Rainy weather during the early growing season
Method of Distribution Rain splash
Wind
Wind dispersal; does not require rain or water Rain water Splashing rain water
Susceptible Tissues All green parts of the vine esp. leaves
Plant structures with stomata are susceptible
All green tissues of the grapevine All new growth during the growing season
All green tissues
Shoots, leaves, rachis
Control of the Disease Sulfur: both preventive and curative, applied as both dust or as wettable powder
Cultural Practices Good soil drainage
Reduce overwintering inoculum
Prune infected shoots
Reduce humidity
Get good air circulation in the vineyard
Provide good light exposure
Canopy management practices to improve air circulation
Remove all mummies during the dormant period
Increase air circulation in the vineyard
Remove diseased canes during normal pruning operations
Link to Cornell IPM pdfs Downy Mildew---Diease Identification Sheet No. 5 1984 Powdery Mildew---Diease Identification Sheet No. 102GFSG-D2 2003 Black Rot---Disease Identification Sheet No. 102GFSG-D4 2003 Phomopsis---Disease Identification Sheet No. 6 Revision 1991
I'm still looking into how to control the diseases organically, so I'll be updating this form. All of the information came from the links to the Cornell IPM pdfs. This form is also located under the tab Fungal Diseases of Grapevines.

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