Hi everyone,

Wow, I see it has been more than a week since my previous post!

Here is something to “tickle” your thoughts.

Many home grape growers use the same irrigation system on their grape vines as on their lawns. Decide for yourself if it is wise or not …

Any form of irrigation normally helps the start and spread of nematodes and fungus diseases, but not all irrigation methods has the same effect. Normal sprinkle and drip irrigation will not have a huge effect on the spread of the diseases, if not applied directly on the leaves of the vine.

There are a few factors that influence the effect irrigation has on the spread of diseases. The interaction of the climate created by the water, the pathogen involved, and the grape variety will influence the spread of the disease.

During irrigation, the microclimate surrounding the grape vine, changes. The water reduces the air temperature, especially when sprinkle irrigation is used. The humidity around the vine, increase due to evaporation of water and it is a known fact the increase in humidity will increase the chances of spreading a fungus disease. Watering a grape vine, will increase the vigor of the vine, as we all know and a more vigorous vine will overshadow bunches. It is found that shaded bunches will be more susceptible to grey rot than bunches in direct sunlight, because the circumstances for spore development and spreading is much better.

The presence of downy mildew during the late summer in countries like Australia and South Africa, is mainly because of the effect irrigation has on the micro-climate surrounding the vine, therefore, you need to sustain your fungus spray program as late as possible.

There are three cycles in the life cycle of a fungus; sporation, spreading of spores and finally the germination and establishment of the spores. A fungus disease like downy mildew needs “free water” for the sporation and establishment of the spores to take place and the water drops of sprinkle irrigation or rain, can spread the spores. The germination then takes place when the climate conditions are ideal and spores will form shortly there after. The whole cycle starts over again and this within 48 hours! Nevertheless, with enough spores present, free water and an ideal climate, this disease will spread like a field fire.

When we look at nematodes, very little grape growers actually know the levels of dangerous nematodes (there are good ones present as well) in their soil. Nematodes damage the roots of the grape vine by attaching itself to the roots and sucking juice from it. This will prevent the roots of the vine to function normal. Nematodes can also cause secondary virus infections like fan leave.

In previous years, farmer from California increased the amount of water they give, to compensate for the loss of water and nutrition uptakes, due to fact nematode damage of the roots of the vine. This had a snowball effect, as more water will spread nematodes much quicker. Nowadays, a more regulated watering schedule and the chemical and biological removal of nematodes decreased this problem dramatically. When planting new vines, make sure your soil is free of nematodes, otherwise your vine will never be a healthy vine.

To conclude this article, I want to urge you to never use overhead irrigation (if possible) on grape vines. The disadvantages of using this irrigation system are so many; it will never justify its use. Rather use a drip or micro irrigation system that will not spray the shoots and leaves of the vine.

When fungus diseases are a big problem in your area, try to water your vines very early in the morning or during the evening. This gives the vines time to dry off, before the temperatures will rise to levels where fungus diseases will spread.

http://www.my-grape-vine.com

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Filed under: growing grapes • how to grow grapes

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