Southern diseases of tomatoes

mensplace · January 12, 2010

From a recent contact from Auburn

"
Last year we saw an increase in fungal and bacteral diseases due to the extended periods of cool, wet weather that favor these forms of pathogens. We will have to see how the weather plays out this year to see how much disease pressure we come under in 2010. One of the best ways to reduce damage from plant diseases is to start off with a healthy plant. In general, a plant growing under stress is more susceptible to disease.
With tomatoes, we really have resistance to only four diseases:
1) Fusarium wilt and (2) Verticillium wilt which both survive in the soil for many years in the absence of disease
3) Root-knot nematodes, which can also survive many years in the soil
4) Tomato spotted wilt virus (TSWV), which is carried from plant-to-plant by thrips (and insect) that transmit the virus while feeding
　
*Verticillium wilt is uncommon in Alabama.
Fusarium wilt is common throughout the state. There are many varieties that have resistance to this pathogen. I would choose a variety that is resistant to Fusarium based on its yield potential in your area and/or fruit quality as it is not possible to differentiate levels of resistance within the various Fusarium wilt-resistant varieties on the market. You may need to do your own experiment to determine which variety you like best in your garden/field.
Root-knot nematode is an organism you can check for through a soil test designed to detect nematodes. These are best done in the Fall at the end of the season when populations are at their highest. A soil test now (January) might not give an accurate reading on this pest because populations plunge with winter temperatures. If you already know you have root-knot in your planting area then you should plant a nematode resistant variety. As with Fusarium it is not possible to choose one root-knot nematode resistant variety over another based on its level of resistance.
Tomato spotted wilt virus has become a more common problem in Alabama in the last 10 years. If you live in south Alabama or have had a history of this disease in your area, then I would suggest planting a TSWV-resistant varieity. However, there are only a handlful of these available with "Amelia" being the best from what I have heard from other growers.
As far as the buffer zone around the garden, it has been determined that about 85% of the viruses that attack tomatoes come from virus-infected weeds that survive the winter within 30 ft of a field. So, if possible, providing a weed-free buffer around the garden prior to planting can reduce virus pressure on tomatoes. Of course, insects can still bring in viruses from other sources outside this buffer zone as many of that plant viruses that infect tomatoes are spread by insects such as aphids and thrips. About 90% of all viruses are spread by insects..
As far as other cultural control methods for a tomato patch. I would strongly recommend avoiding overhead irrigation. Water once or twice a week using drip irrigation or soaker hoses, if possible, in an attempt to keep the foliage dry. Wet foliage provides conditions that favor development of both fungal and bacterial foliar diseases."

January 12, 2010	#1
mensplace Tomatovillian™ Join Date: Dec 2009 Location: USA Posts: 1,013	Southern diseases of tomatoes From a recent contact from Auburn " Last year we saw an increase in fungal and bacteral diseases due to the extended periods of cool, wet weather that favor these forms of pathogens. We will have to see how the weather plays out this year to see how much disease pressure we come under in 2010. One of the best ways to reduce damage from plant diseases is to start off with a healthy plant. In general, a plant growing under stress is more susceptible to disease. With tomatoes, we really have resistance to only four diseases: 1) Fusarium wilt and (2) Verticillium wilt which both survive in the soil for many years in the absence of disease 3) Root-knot nematodes, which can also survive many years in the soil 4) Tomato spotted wilt virus (TSWV), which is carried from plant-to-plant by thrips (and insect) that transmit the virus while feeding 　 *Verticillium wilt is uncommon in Alabama. Fusarium wilt is common throughout the state. There are many varieties that have resistance to this pathogen. I would choose a variety that is resistant to Fusarium based on its yield potential in your area and/or fruit quality as it is not possible to differentiate levels of resistance within the various Fusarium wilt-resistant varieties on the market. You may need to do your own experiment to determine which variety you like best in your garden/field. Root-knot nematode is an organism you can check for through a soil test designed to detect nematodes. These are best done in the Fall at the end of the season when populations are at their highest. A soil test now (January) might not give an accurate reading on this pest because populations plunge with winter temperatures. If you already know you have root-knot in your planting area then you should plant a nematode resistant variety. As with Fusarium it is not possible to choose one root-knot nematode resistant variety over another based on its level of resistance. Tomato spotted wilt virus has become a more common problem in Alabama in the last 10 years. If you live in south Alabama or have had a history of this disease in your area, then I would suggest planting a TSWV-resistant varieity. However, there are only a handlful of these available with "Amelia" being the best from what I have heard from other growers. As far as the buffer zone around the garden, it has been determined that about 85% of the viruses that attack tomatoes come from virus-infected weeds that survive the winter within 30 ft of a field. So, if possible, providing a weed-free buffer around the garden prior to planting can reduce virus pressure on tomatoes. Of course, insects can still bring in viruses from other sources outside this buffer zone as many of that plant viruses that infect tomatoes are spread by insects such as aphids and thrips. About 90% of all viruses are spread by insects.. As far as other cultural control methods for a tomato patch. I would strongly recommend avoiding overhead irrigation. Water once or twice a week using drip irrigation or soaker hoses, if possible, in an attempt to keep the foliage dry. Wet foliage provides conditions that favor development of both fungal and bacterial foliar diseases."