Fruit Grower's Tips: Information About Eutypa Dieback

Grape eutypa dieback is a plant disease caused by the fungus eutypa armeniacae. The pattern of damage and how to repair.

What is it?

Grape eutypa dieback is a plant disease caused by the fungus eutypa armeniacae. Eutypa armeniacae is known for its pattern of doing severe to moderate damage for two to three years in a row and then disappearing for a time to reemerge and repeat the cycle of fungal infection again.

What does it look like?

Eutypa armeniacae appears as dark, irregularly shaped spots on young grape leaves. As the infection progresses the spots may drop out of the infected grape leaves entirely, leaving a hole in their wake. The new season's grape canes will also develop sunken irregularly shaped spots. When eutypa dieback occurs, the growth of shoots may appear stunted or weak and the leaves will be small and yellowish. Often the grape leaves are cupped looking and have crinkled edges that can turn brownish as the infection progresses. Late in the season, the grape leaves may appear to be scorched and tattered looking where previously sunken spots have dropped out and left ragged holes that catch in the wind. The sunken lesions may also develop on the otherwise strong woody grape canes and trunk of the grape plant. If the fungal infection of Eutypa armeniacae become severe, entire grape branches may die and drop off the grape plant.

How does it manifest?

The eutypa armeniacae fungi can survive the winter on the trunk or branch cankers which were infected the prior growing season. Then when water splashes them, the infected wounds carry spores to other pruning wounds on unifected areas, infecting them. The formation of these sunken areas, or cankers, reduces the flow of nutrients and water to areas of the grape plant from the trunk and braches. This causes the portion of the grape plant above the sunken canker site to be starved of essential nutrients and untreated that area may eventually die off.

What can you do about it?

You must prune out and destroy all infected branches and canes which show eutypa armeniacae damage. Additionally, make sure to prune later in the season, more toward winter which will prevent spores entering pruning wounds and over wintering there. Make sure that when you do prune, your cut is at least 6 inches below the region of any canker or discolored wood. If the trunk is riddled with cankers, you will need to remove and destroy the entire plant by cutting below the lowest canker, while staying above the bud union trying to maintain at least 2 suckers per trunk. You can treat fresh pruning wounds with a benomyl containing fungicide which can help prevent infection. Unfortunately, eutypa dieback infection means you won't get a crop of grapes this growing season, but you will yield a normal crop the following year if you follow the above measures and treat the fungal infection properly.

© High Speed Ventures 2011