Possible fertilizer burnout
Good morning. I put some fertilizer around some shrubs and some new (less than one-year old) grape vine plants about a month or so ago and have noted that the leaves are falling off some the plants and others have a white-ish powdery-like color. I interpret this has having over-fertilized them. Will it help if i dig them up and place new soil around them? Are there any other steps i may take?
Montgomery County Maryland
This sounds more like powdery mildew, which is a white growth on leaves which can be wiped off. This arises each season based on temperatures and humidity and pathogens. Some plants are more susceptible than others, including grapes.
Like all disease in the landscape, there are things you can do to lessen the impacts of powdery mildew, including selecting resistant varieties, siting, spacing or pruning plants to increase airflow, and keeping the leaves as dry as possible by watering early in the day to allow for sun and air to dry the water and not allow it to sit on the leaves for long periods of time.
That does not completely rule out fertilizer burn, but if you followed the label instructions for application, it shouldn't have hurt, unless it made lots of lush growth, which again can sometimes lead to disease problems, and with blooming plants, lots of leaves at the expense of flowers.
No, you do not have to replace the soil.
Thanks for the quick response. OK. I have the white powder on a couple of plants and dropping leaves on a couple of plants, including a grape plant that appears to be (possibly) dying. Will the mildew kill the plant, i.e., is the mildew far enough advanced to have caused the leaves to drop, etc., or could I possibly have two different problems here? And other than wiping the leaves, is there anything else I can do? The grape vines are about ... 2-3 feet apart. Should I move them further apart?
We meant the wiping of leaves for diagnostic purposes only, not that you should do that.
Can you identify all of the plants we are talking about here?
Can you take some clearly focused digital photos to let us see not only the whole area, but some closer ones of the affected plants? This would help us to better help you. They could be attached to this reply.
Powdery mildew is not usually fatal, especially if this is the first time you have had it. It doesn't necessarily repeat every year, but is based on weather and pathogen loads.
Grapes, like fruit trees, often need a regular spray schedule to control for pests and diseases. Grape plants are usually spaced about 6-8 feet apart, so yes, that is too close.
I will have to take some pictures this evening and send them tomorrow. But I take it that I should go ahead and move the grapes further apart? They are roots from plants planted by my grandmother that I moved here last fall when the family farm in Ky. was sold.
OK, we will look for your photos. You can move the grapes further apart, and keep them well watered up until the ground freezes in the winter.
Our Getting Started with Small Fruits publication may be of help: