My 4 year old grape vine is in a sunny spot getting 8-9 hours of sun in Mississauga ontario has developed pinkish red spot on leaves. Will up load a picture.
What to stop and prevent it?
Thank you for contacting the Toronto Master Gardeners regarding the pink spots appearing on your 4 year old grape vine. There are several disease / pest possibilities that may be causing the spots on your vine. However, the damage by any of these common pests and diseases does not quite match the bright pink of these spots. Nonetheless, several diseases that can cause red coloration and spots on grape leaves include:
Grapevine Leafroll virus causes red colouration and blotchiness of leaves but typically appears in late summer or early fall. Likewise, Grapevine Red Blotch virus, a more recently recognized virus in our area, causes red veins and blotches on leaves, but also typically in the fall.
When extreme, potassium deficiency can cause red colouration of leaves but not typically in a blotchy pattern such as you have. Since you have had your vine for 4 years, if nothing significant has changed with your soil or plant care, this is less likely.
The Erineum Mite (Colomerus vitis) overwinters in galls (abnormal growth of plant tissue caused by feeding or egg laying of insects), which can appear as pink or reddish colouration on early shoots and leaf tissue. A link to information and photos of Erineum mite gall is attached for your reference.
The leaf surface in your photo is irregular (bumpy) and that may also be related to gall formation. In most cases severe injury to the plant is uncommon and no specific treatment is needed. In the case of a light infestation, the afflicted leaves can be removed.