Tomatoes, Part 2: Soil, pests and diseases

2014-03-14T17:00:00Z 2014-07-03T12:05:27Z Tomatoes, Part 2: Soil, pests and diseasesSusan Billings Arizona Daily Star Arizona Daily Star

Now that you're ready to plant, be sure to use the right amendments to ensure healthy plants.

Soil composition and other amendments: 

Your garden likely needs sulfur. Our natural desert soil has a pH of about 7.5 to 7, which is alkaline. A pH of 6 (slightly acidic) is ideal. However, if you have raised beds or containers, in which you are not using native soil, it will already be adjusted for proper pH, Carolyn says. I always sprinkle a couple of handfuls of soil sulfur into the garden bed with the other amendments, but Carolyn suggests putting 2 tablespoons per plant at the bottom of each planting hole. Also:

  • Dolomite lime: Tomatoes and peppers need a certain amount of calcium and magnesium for optimum health. Follow directions for in-ground application. In pots, add about 2 tablespoons to the bottom. 
  • Magnesium sulfate: Sprinkle and work into the top 2 inches of soil. Hint: If your plants are deficient, you’ll see the lower leaves turn yellow. If you’ve already planted your tomatoes, that’s OK. Just sprinkle on top of the soil and water it in.
  • Bone meal: This adds phosphorus and promotes healthy roots and fruits. However — and it’s a big caveat — be careful if you have a dog. They love the smell and taste, and it will make them very sick if they eat it. My dog Max did just that and was violently ill for three days.
  • An alternative for dog owners is soft rock phosphate. Harlow Gardens carries an organic version by Dr. Earth.

Temperature and pruning:

Here’s another thing I didn’t know: When the mercury hits 90 to 95 degrees, most tomato plants start shutting down. The exception is cherry tomatoes, which would explain why they were my only tomato success last summer. However, your bigger plants will likely “rest” for the hottest part of the summer, then perk up when it cools off.

So in August, after the first crop is done, cut plants back to 2 feet or so and let them grow back. The new growth will produce another crop.

Pests: 

How about some good news? We don’t have many pests here in the desert. Like Canadians and Red Sox fans, they just can’t handle our brutal summers. The exceptions (especially in the spring and fall) are:

  • Whiteflies: Spray an organic product such as Captain Jack's Deadbug Brew to kill the nymphs that gather on the leaves. To kill the adults, try sticky fly traps. 
  • Spider mites: Look for webbing and dust. Hose them off once a week to keep spider mites at bay.
  • Aphids: They disappear with the summer heat. You can control them with natural products, which are made with things such as rosemary oil and peppermint oil. Spray them in the early morning or evening.
  • Caterpillars and hornworms: I’m not sure I’ve ever seen a hornworm, but Carolyn’s description made me shudder. Don't pick them off the plant, as they’ll just dig in and damage the stem. Pick up some of Captain Jack’s Deadbug Brew and spray the little buggers. Or try Dipel Dust, a powder form of BT. Carolyn’s tip: Don’t use the liquid form of BT in the summer — use the powder.
  • Ants: This was my question, as they attacked gardeners at our community plots in midtown last summer. And the bites itched like crazy. So, try to find their mound and pour cornstarch on it. (I definitely plan to try this, but let us know if you’ve tried it and if it works.) Also, Carolyn recommends 38 Plus, which works on leaf-cutters and other biting ants, too.

Diseases:

Again, here’s some good news for desert dwellers. Diseases can’t stand the heat and dryness for the most part. But there are exceptions:

  • Early blight and late blight, caused by fungus. Prevent this by watering in the morning or using a copper fungicide if blight develops.
  • A similar condition is caused by magnesium and calcium deficiencies, which can mimic blight. Prevent these by amending with magnesium sulfate and dolomite lime when planting.
  • Blossom-end rot: The tomato appears fine until you look at the bottom, which will have a brown spot. It’s still edible, as long as you cut off the brown spot. But try dolomite lime or Rot-Stop, which is a liquid calcium that you spray on the plant. It works for bell peppers, too, Carolyn says.
  • Powdery mildew: Use a copper fungicide, an organic product that you spray on the soil. Powdery mildew is an airborne spore that can travel easily through your neighborhood on windy days.

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