Tomato Blight

Asked September 1, 2014, 10:31 AM EDT

I live in the Irwin, PA area and have had a tomato blight problem for the past few years. I have tried various disease sprays and copper solutions to no avail. The problem was really bad this year.

Each year after my garden is done; I clean out all of the remaining plants and weeds as possible. The debris is discarded far from the garden. I then till the ground before the frost sets in.

Is there anything that can be spread on the soil and tilled into the ground that will kill any reaming spores? I attached a photo of my six remaining plants I took this morning, Sept. 1, 2014. Thanks for your help.

Westmoreland County Pennsylvania plant pathology horticulture

3 Responses

There are several diseases that could cause the symptoms that you are seeing. Early blight and Septoria leaf spot are diseases that can survive overwinter in the crop residue so cleaning out the garden will be helpful. Moving the location of the tomatoes in the garden each year will also help. These diseases typically start to develop on the lower leaves when the plants start producing fruit. It is important to start using copper or any other fungicides before you start seeing symptoms. Also make sure that you get very good coverage because these products will only protect the surfaces which they come in contact with.

Late blight is a very different disease that was particularly devastating this season. A fact sheet with additional information about this disease and its management can be found here http://pubs.cas.psu.edu/freepubs/pdfs/ul215.pdf.

Thanks for the information and quick response to my inquiry. In my opinion, it looks like the home gardener can’t do much to fight plant diseases when the weather conditions are favorable for them to take hold. I do move the plants around in my garden from year to year but the distance from where they were the year before is not that great.
I was surprised that there is nothing that the home gardener can till into the ground in the fall that would kill various spores and bacteria which cause the maladies. I would imagine there is something available for the commercial growers to use. Like with many great pesticides and other chemicals that have been banned for home use. Big Brother EPA and DEP doesn't trust us to use them responsibly. I do not like to use many chemicals in my garden but there are circumatances where they must be used.

Many of the pathogens that affect tomatoes in home gardens are associated with the crop residue. So removing all the crop residue at the end of the season is important. Commercial growers will use crop rotation to help manage these diseases and rotate out of plant families for 3 to 4 years. This allows the crop residue to thoroughly decompose and the reduces the pathogen populations because many of them can not survive in the soil on their own without host plant tissue. This is much more challenging in a home garden where you are more confined by space. Mulching the soil to create a barrier between the soil and your plants will help. Watering at the base of the plants and avoiding getting the leaves wet will also help. Many pathogens require leaf wetness or high relative humidity to infect. During the season you can use products that contain the active ingredients chlorothalonil or copper to help protect the plant surface.These are best applied before you start seeing symptoms on the plants. When using these products always follow the label. Several options can usually be found in many garden centers. Also when you start seeing symptoms, removing those leaves can help reduce spread to other plants. An integrated approach using many tactics is usually the best way to try to manage disease both in the home garden as well as in commercial production.