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Garden Help Desk: Keep an eye on your tomatoes this summer

By USU Extension - | Jul 16, 2022

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Plants that are affected with the mystery tomato disease develop yellow leaves as they decline.

Something disheartening about gardening is having plants die through no fault of your own. This year it is happening to tomatoes in many areas of the county, and along the Wasatch Front. There have been numerous calls to the Utah County Extension office from local gardeners concerning this. Neighborhood-sized areas can be affected while adjacent areas are not.

Roma-type paste tomatoes seem to be dying at greater rates than other varieties, although other varieties are also declining. The affected plants appear to be stunted, turn light green, then yellow with some leaf scorch developing on the leaves, and then they die. This decline happens over in the span of a few weeks.

The initial suspect was a viral disease — Curly top. It’s spread by an insect called the beet leaf hopper, and there have been reports that leaf hopper pressure is heavier than normal this year. However, the affected tomato plants are declining faster than expected with curly top disease, and there seems to also be a lack of good root development mixed with some root rot on infected plants. The only conclusion so far from samples submitted to the Utah State University Diagnostic Lab campus is that curly top doesn’t seem to be the cause. Additional tests are being done.

No matter what is going on, there is most likely not a spray treatment to stop the plants from declining or getting infected. It’s discouraging but digging infected plants from the garden and throwing them away is all that can be done. Do not compost the affected plants or tomatoes either.

There may be some garden centers in Utah County that still have tomato plants, but if they do it won’t be for much longer. If you can find short season varieties such as Early Girl or Fourth of July, you may still have time to replant to get a crop towards the end of the gardening season. There is also still time to plant short season sweet corn and green beans. The time to plant cool season crops for late fall harvest is also quickly approaching. Some of these could be interspersed among the remaining tomatoes.

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It's best to remove tomato plants affected with this mystery disease because it's very unlikely they'll recover and be productive.

Even though it’s not certain what is causing this relatively widespread tomato decline, it is happening. The silver lining in all of this is that there still should be enough healthy plants around that we can still enjoy locally fresh tomatoes, even if they may not have come from our gardens.

I have about eight fruit trees that have been in the ground between 2 and 6 years. Most of them were planted bare root. How much water should they be getting and how frequently? Can you give me quantifiable amounts of time or water for when we run our drip system? We are trying to figure out if the trees are getting enough. With the dripline system we’re wondering if we put on all the water on at once or if we should water in several increments through night.

There isn’t a one-size-fits-all amount of time or water for landscapes. Your soil type, the size and kind of plants, the water quality, the time of year, the weather and any microclimates in your landscape are all factors.

Most of the feeder roots on an established tree are in the upper 6-24 inches of the soil. You’ll want water to move at least 12-18 inches down into the soil to give your tree a deep soak, but you don’t need to water them frequently. Your established trees should always get a deep soak, but not more than once a week during the heat of summer and less often in the spring and fall. Try modifying your drip system just a bit to make sure part of the system will water a place in your home orchard where nothing is growing. Run your drip system for about an hour, wait several hours and then dig down in the place where nothing is growing and see how far the water has moved. With that information you can do a little math to determine how long you need to run your system for your fruit trees in your soil.

Make sure you consider all the water sources for your trees. If your fruit trees are in the lawn, or within 10 feet of the lawn, you should consider the lawn watering to be tree watering, as well.

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Stunted growth, pale color, rolling or curling leaves and twisted growth are some symptoms of the mystery tomato disease.

There’s no need to run your drip system with multiple short segments. The drip system is already going to give a slow soak. If you need to divide the watering time you can run your drip for half the needed time, wait an hour or so, and then run it for the second half.

When fruit trees are planted near lawns, the lawn watering should be included in any fruit tree watering calculations.


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