What’s the matter with my grape?

Question: I’m observing these black spots throughout my grape vine, and some leaf die off. What is this, and do you have suggestions on how I could treat it? I believe it is a Flame Seedless. 

Thank you!

responder: Regards,  Replied July 22, 2023, 1:16 PM EDT
response: Hi Amy,   I think this question should go to a specialist in grapes. And I only have time for 2 questions / week which I completed early this week.Madeline Bakarich On Jul 21, 2023, at 3:24 PM, Ask Extension <<personal data hidden>> wrote:﻿Hi Madeline, Question #0111850 has been assigned to you by Amy B. What’s the matter with my grape? I’m observing these black spots throughout my grape vine, and some leaf die off. What is this, and do you have suggestions on how I could treat it? I believe it is a Flame Seedless. Thank you! From: Gretchen DrewSubmitted: 07/21/2023 4:34 PM To view/respond to the question, please login. Please join the Ask Extension Experts group in Connect Extension. We will use that group to post updates about Ask Extension.This message was sent by Ask Extension. If you need help, please visit https://askhelp.extension.org/.

responder: The Question Asker Replied July 22, 2023, 1:28 PM EDT
response: Hi,I don’t think this email was meant for me. My question is still open. Thank you,Gretchen On Jul 22, 2023, at 10:16 AM, Ask Extension <<personal data hidden>> wrote:﻿

responder: Regards,  Replied July 22, 2023, 1:38 PM EDT
response: Sorry I am new to this quorum MadelineOn Jul 22, 2023, at 10:28 AM, Ask Extension <<personal data hidden>> wrote:﻿

responder: The Question Asker Replied July 22, 2023, 2:33 PM EDT
response: That’s fine, Madeline. I see my question is listed as “Closed”. Can you please make sure it is reopened?On Jul 22, 2023, at 10:38 AM, Ask Extension <<personal data hidden>> wrote:﻿

responder: An Ask Extension Expert Replied July 24, 2023, 1:40 PM EDT
response: Thank you for your question and for reaching out to Ask Extension. Your grapes appear to have a powdery mildew infection. Powdery mildew of grape is a fungal disease that can infect grape leaves, shoots, and clusters early in the season and is exacerbated by cool and moist/humid conditions. If you aren't seeing it already, you may see some of the mildew start to grow on your grape clusters. Right now you can use several things to treat the infection. Sulfur fungicide is the most common for backyard grapevines with several commercial formulations available at most hardware stores. Be careful not to apply the sulfur when you have 90 °F or higher in the several day forecast. Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens is another fungicidal product that does not have the same temperature threshold, but may be harder to find.  Next year and in future years, you should consider the following actions: Reducing the density of shoots and leaves in the cluster zone to provide adequate airflow. This can reduce the conditions that promote powdery mildew growth.Applying a horticultural oil just prior to budbreak and early in the season during shoot growth.Applying a sulfur fungicide during early shoot growth, during bloom, and after bloom. Do not apply horticultural oil within two weeks of a sulfur application.Dispose of infected plant tissue (clusters, leaves, shoots/canes) offsite at the end of the season to reduce overwintering fungal inoculum. I would highly recommend reading the following article on grape powdery mildew: https://pnwhandbooks.org/plantdisease/host-disease/grape-vitis-spp-powdery-mildew. Powdery mildew is the most common disease of grapes but can be well controlled through cultural (i.e., shoot and leaf removal) and chemical (i.e., sulfur) methods. Take note that powdery mildew will be worse in years with cool and wet springs. If you have additional questions related to grapes, powdery mildew, or other topics, please don't hesitate to reach out to Ask Extension. Cody Copp, Oregon State University

responder: The Question Asker Replied July 24, 2023, 2:06 PM EDT
response: Thank you so much for your help! Here’s hoping I can save some of this year’s fruit. On Jul 24, 2023, at 10:40 AM, Ask Extension <<personal data hidden>> wrote:﻿