Tomato leaf spots

Asked September 29, 2019, 7:05 AM EDT

My tomato plants suffered horribly from tomato rust. I got very few tomatoes this year despite taking off affected leaves, spraying with neem oil etc. what can I do to prevent this next year?

Livingston County Michigan integrated pest management plant disease tomato problem

3 Responses

Hello,

I don't know of a common tomato rust disease in Michigan. Are there any pictures you can send me of the issue? Perhaps you had septoria leaf spot or early blight.

I would definitely try to select some disease-resistant tomato varieties to plant next year. These would not be resistant to all diseases, but you can find tomato cultivars that were bred to be resistant to certain common diseases like tomato early blight and late blight, verticillium wilt, fusarium wilt, and others. Using resistant varieties doesn’t mean the plants won’t get the disease at all, but the symptoms shouldn’t be as severe.

Cornell has lists of vegetable varieties, including different types of tomatoes, and their reported resistance to developing different diseases. Here is the link: http://vegetablemdonline.ppath.cornell.edu/Tables/TableList.htm

Are the tomatoes being grown in full sun? Have you a had a soil test done for your garden area? https://homesoiltest.msu.edu/

Also consider going to our MSU Extension Gardening in Michigan website and checking out our resources on growing vegetables, including our Smart Gardening vegetable tip sheets.

Proper water and wetness management can help avoid tomato disease. Water the plants at the base and keep the tops of the plants as dry as possible. Also, space plants well and prune to promote air circulation. Most diseases need wetness on the surface of the plant to infect it, so the drier you keep the UPPER part of the plant, the less chance for disease development.

You can also try mulching around the tomato plants, with organic or plastic mulch, to avoid having soil splash onto the upper part of the plant. Disease particles can overwinter in the soil.

Also, do you rotate where you grow your tomatoes each year? Crop rotation can help prevent build-up of disease inoculum in one spot.

Do try to identify the main disease issue that you had this year, so that if you believe it is necessary to spray a pesticide next year, you can be more knowledgeable about proper timing (which is very important) and the most appropriate product to use. Always read and follow all pesticide label directions. The label is the law. If you’d like, you can send a sample to MSU Plant and Pesticide Diagnostic Services. Routine plant analysis is $20. Otherwise, send in some photos through Ask an Expert, as I said, but it’s not always possible to determine the specific disease issue from photos. Worth a shot though.

Here are a few resources from the Hausbeck Lab at MSU that could be helpful:

Cornell also has a Tomato Disease Identification Key.

This Tomato diseases, insects and disorders webinar from Ron Goldy at MSU Extension might also be helpful.

Please let me know if you have further questions.

Regards,

Irene

Thank you for the prompt and thorough response Irene. I believe the disease is Septoria leaf spot. Call it rust because when removing diseased leaves, my garden gloves get a coating of rust colored dust always. I treated with Neem Oil spray since my garden is organic.took pic this evening and will include.
by the way this is a small two bed raised organic garden. I did have the soil tested and added organic fertilizer this spring. Next year I will rotate the tomatoes to the other bed.
do you have any info on prevention next year and treatment if reoccurs? Thank you, Patricia Murphy

Hello Patricia,

I showed the picture to the plant diagnostician at MSU Plant and Pest Diagnostic services (pestid.msu.edu) and she said "I might lean more toward a nutritional issue, but I would need to see more of the plant. Do you have any images of the entire plant?"

So please, send a more zoomed-out photo of the entire plant, if possible.

A bacterial disease, such as Bacterial speck, might also be a possibility. See articles:

http://blogs.cornell.edu/livegpath/gallery/tomato/bacterial-speck-of-tomato/

http://u.osu.edu/vegetablediseasefacts/tomato-diseases/bacterial-speck/

Note: Many of the recommendations will be applicable, but some are only applicable to commercial growers.

Do you see any spots on the tomatoes themselves? If so, can you send a photo of that too?

Neem oil is not intended for use as a bactericide (to kill/protect against bacterial pathogens).

Some products with a copper compound as the active ingredient can be used as both a fungicide and bactericide.

Read the label. You should find both the plant you want to treat (tomato) and the specific disease on the label. That's why it's important to have a good idea about what you have or have had in the past before you treat.

Of course if it's a nutrient issue, spraying a pesticide is not going to help.

Here is some more fungicide/bactericide information:

Homeowner’s Guide to Fungicides from the University of Kentucky

Two examples of copper product labels below. I am not specifically endorsing any products.

Natural Guard Copper Soap Fungicide by Ferti-lome

Bonide Copper Fungicide RTU


Thanks,
Irene