Grass, tomatoes showing signs of disease, plant injury this spring

Published 12:00 am Sunday, May 30, 2010

I have been out several days over the last two weeks but after getting in and returning a number of calls, it is clear we are having trouble in two areas, lawns and gardens. It seems to be a tough year for some of you growing tomatoes, and it seems some of the lawns are having some stress to.

Q: What could be killing my Bermuda or St. Augustine lawn?

A: Dead spot is probably the most destructive turf pathogen affecting Bermuda lawns. The causal organism of spring dead spot is ophiosphaerella a soil borne pathogen considered to be indigenous to most southern U.S. soils.

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Spring dead spots are generally round in shape and can range from 6” to 1’-2’ in diameter, but in severe cases, the spots will coalesce into large, irregular patches. The infected turf is actually dead as the name suggests and will have to be replaced or encouraged to fill in from the edges.

Weak turf that is under stress from, agronomic, physical or climatic factors is especially vulnerable to spring dead spot. This may be why we have seen so much of it this spring due to the harsh wet and cold winter, combined with weeks of hot, dry and humid weather.

The pathogen actually infects the turf’s root system in the fall eventually causing the plant’s vascular tissue to clog preventing the normal flow of water and nutrients. Over the course of the winter when the turf is dormant, there are no symptoms evident and everything appears normal.

In the spring though, as the weather begins to warm, the infected turf is unable to draw upon reserves of water and nutrients to break dormancy.

Some affected turf may appear to green up as healthy turf would, but it quickly declines as the plant is starved for energy from the clogged vascular tissue. Research to this point has not found a consistent cure for this disease in Bermuda lawns.

The most troubling disease faced with St. Augustine lawns is brown patch or large patch. This disease is easy to recognize as the fungus starts in a small area usually circles, and the circle slowly begins to grow and increase in size. Brown patch along with gray leaf spot are both controllable with applications of fungicides.

Brown patch usually will not kill the lawn just severely injure it sometimes taking months or more to return to its normal appearance. I have not had any calls in the last month relating to brown patch because the environment has been hot and dry. However with chances of rain several days next week be on the lookout for development and be proactive should signs occur.

Q: What is going on with the tomatoes this year?

A: So far I have seen problems with blossom end rot, bacterial wilt, water wilt, insect infestations and herbicide damage.

Many of these can lead to loss of plant or fruit decline. To start do not spray herbicides around tomatoes as they are very susceptible to plant injury. Try to remember to manage your soil as good as possible.

Bacterial wilt, blossom end rot, and water wilt all can relate to soil conditions.

There have been several reports of tomatoes not fruiting this spring. This is frequently caused by too much fertilizer being applied. This applies to other vegetables too. When we apply excessive fertilizer the plants tends to stay in the growth and foliage stage longer, just be patient the fruit will likely come.

David Carter is the director of the Adams County Extension Service. He can be reached at 601-445-8201.