Older grapes require deeper, less frequent watering
Question: My grapevines are not growing as usual. I have had them for seven years. They always give me nice big leaves, but this year, they are very small and brown like they are dying or lacking something.
Before we get into some more difficult problems, please make sure they are getting watered with enough water at each application and the timing of the irrigations is correct. The bigger the grapevines, the more water they will require.
It is hard for me to tell you how much water to give them without knowing if you have them covering a large area such as a patio or if they are highly restrained on a trellis as you might see in a vineyard. Also, make sure they are not watered too often, such as daily, or this could cause some problems like you are describing as well.
Highly restrained and trellised grapes might be irrigated with perhaps only 10 to 15 gallons at each application, while an unrestrained vine might require twice this amount or more.
Grapes have the capability of growing very deep roots – 30-60 feet under the right conditions. Most fruit trees do not have this capability. In our soils and conditions, deep-rooted grapes are highly unlikely because there are very few places where they can tap into water at this depth. So that being said, let’s assume you will be watering them like a fruit tree.
Try deep watering your grapes first. Then, to be on the safe side, please contact the Nevada Department of Agriculture in the Las Vegas office and coordinate a sample to be sent to the state plant pathologist for examination .
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at extremehort@aol.com. Visit his blog at xtremehorticulture.blogspot.com.