My Grapes Turn Brown And Black And Rot Before They…
Jason Asked
My grapes turn brown and black and rot before they are ripe. I think it might be some kind of fungus. Is there any way to determine exactly what the cause is?
The Gardener’s Answer
Hello, Jason: There are many different species of fungus that attack grapevines. Many of these can cause the actual fruit to rot. Each has its own characteristics so I cannot say for certain what specifically is going on with the grapes in your garden. For a positive identification you can take a sample to your Cooperative Extension Service for them to analyze in the office or to have sent off to one of the land grant universities in your state to diagnose. Typically the most common fungal problem associated with grapes is caused by the fungus Guignardia bidwellii, which causes black rot. The infected berries shrivel up and look more like raisins than grapes. Different varieties of grapes are more susceptible than others. It can be controlled by good sanitation and potentially a spraying program, but the most important step in eliminating the problem is to have it positively identified. Fungal problems will overwinter in the soil and on any plant debris, so good sanitation practices are essential in terms of controlling disease problems. For now, remove and dispose of all infected grapes still on the vine, as well as the ones that have fallen, and keep the area around your grape vines clean. As with all plant material, they are more likely to be attacked by insect and/or disease problems if they are stressed by environmental conditions. This is why it is so important that we give them ideal growing conditions to thrive in. Grape vines should be planted in full sun with good air circulation. The Franklin County Web site is http://franklin.osu.edu/.
