Leaves on Tomato Plants Drying Up

Daniel Gill  |  7/1/2015 12:15:54 AM

Dan,

We have tomato plants in pots in our backyard. We started most of them from seed back in February in a greenhouse. We have about 20 plants. We have gotten quite a lot of tomatoes off of them in the past months. Now the leaves are drying up. They may have blight. If they do have blight, is the soil now contaminated to the point of having to dispose of it? Also, are any of the tomatoes that came from them bad and are they edible? We bought some little plants last week. Part of one of the plants is starting to look bad. If it is the blight can I treat it with something? Thank you.

- Tom J.


The main tomato crop has been set by now and most of it has been harvested. At this point the spring/early summer tomato season is winding down for most home gardeners. Disease control is particularly important in April and May and even into June. But by late June, with so little of the season left and most of the crop harvested, it’s hard to justify an aggressive fungicidal spray program for your old plants.

There are many common fungal foliar diseases that attack tomato leaves – such as early blight, late blight, septoria leaf spot, bacterial leaf spot, etc. Send me some pictures of the symptoms on the old plants and new transplants. These diseases are spread by aerial spores that drift in the air. Their presence does not mean your soil is contaminated. The only precautions I would take are – as leaves become unhealthy or turn yellow, pick them off and dispose of them in the trash. When you pull the plants up (which will be when you harvest your last tomato), don’t throw them in the compost pile. Dispose of them in the trash.

By no means should you consider replacing the soil at this point.

As to trying to grow tomatoes during the incredibly hot mid to late summer period, you may plant tomatoes now for late summer production. You must be sure and use special varieties that are able to set fruit in heat. Most commonly grown varieties that we plant in spring will not set fruit in the heat. Most home gardeners only grow one crop of tomatoes – the early summer crop; some also plant a fall crop by planting transplants in August or early September (south LA) for production in the mild fall weather in October and November.

Producing tomatoes in late summer is much more challenging than producing the main early summer or fall crops. Expect lots of insect and disease problems. Pay careful attention to watering as the soil can dry rapidly in the heat. Be sure to keep the plants well mulched to prevent the soil from getting so hot. But, if you are up for a challenge, you can try a late summer tomato crop.

To prevent disease problems, spray the plants weekly with chlorothalonil (Daconil and other brands) and to minimize insect problems spray weekly with permethrin (Bonide Eight and other brands) following label directions carefully.

Here’s a link to our online tomato publication:

Tomatoes

Dan Gill
Consumer Horticulture Specialist

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