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Saturday, May 12, 2012

Scorching Brown Leaves of Grapes May Be More Than Water

Q. My grapevines are not growing as usual. I have had them for 7 years. They always give me nice big leaves but this year they are very small and brown around like they are dying or lacking something?

A. 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 are correct. The bigger the grapevines, the more water they will require.

            So it is hard for me to tell you how much water to give them without knowing if you have them covering a large area like a patio or if they are highly restrained on a trellis like 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, like you see in a vineyard, 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; thirty to sixty feet under the right conditions. Most fruit trees do not have this capability. In our soils and conditions deep-rooted grapes are highly unlikely since 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.

            If watering is adequate then we can look at some less likely problems such as Pierce’s disease that is carried by an insect called the glassy winged sharpshooter. To date this disease and insect has not been reported in Southern Nevada. 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 and his comments.

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