Margaret Lauterbach: Keeping your Treasure Valley tomato plants healthy

Special to the Idaho StatesmanMay 30, 2014 

Are you gardening in containers?

Terri Gillingham, now living in Washington but formerly a master gardener in Ada County, discovered that planting a tomato in a trench sees roots adapt to the depth without harm to the plant.

We've always been advised to plant tall, leggy tomato plants lying in trenches, but the unspoken assumption was they'd behave as usual tomato roots do: that is, plunge as deep into the soil as possible. Gillingham found by experience the plants will put out enough roots in an 8-inch-deep planting box to sustain the entire plant without a reduction in fruit. Each of the tiny bumps on a tomato stalk will become a root once it meets soil.

Since the roots are close to the soil surface, they receive more heat from the sun than tomato roots usually do, and respond appropriately, Gillingham thinks. They would require frequent watering, however.

In-ground tomatoes should be watered deeply, once a week by irrigation. Sprinkling wets foliage, inviting disease.


Boise friend Lindarose Curtis-Bruce found her asparagus producing sparsely this year, and dug down to inspect the roots. Most of the roots had been consumed by wireworms, caught in the act. Some call them wax wireworms because of their shiny yellow to orange segmented bodies.

These are the offspring of long slender beetles that some call "click" beetles. They are so jointed that, when they fall onto their backs they can right themselves by raising their head and prothorax (upper chest, attached to the first pair of legs), then suddenly straightening, propelling themselves into the air with an audible click.

The adult color is usually brown or black, their sides parallel, the wing covers on their backs grooved front to back and about one to three centimeters in length, or no more than an inch and a quarter long. They lay eggs shallowly in soil.

Wireworms may exist and feed on root crops and corn for several years before they pupate and emerge as click beetles.

To control these larvae, thrust a carrot (preferably with top attached) or a cut potato into the soil, then two or three days later, draw out your bait and destroy any wireworms found. Replace the bait to catch more. Or drizzle molasses on a fencepost to catch sweet-loving adult click beetles.

Wireworms burrow into carrots, sugar beets, potatoes, sweet potatoes, other root crops and flower bulbs, too. In large numbers, they can be very destructive.


Damp spring weather may leave other unpleasant reminders to gardeners: rust on leaves, stems, shoots and fruit.

How many times have you seen brick-red spots on leaves of plants such as hollyhocks or weeds or grains or beans or corn?

That is rust, and it's difficult to control. Remove and burn or send to landfill all leaves that show that disease. Never put them in compost, for they contain spores (seeds) of future rust infections.

Rust is a parasitical fungus, usually not fatal, but it can stunt plants, turn leaves yellow and reduce yield. Yellow leaves still have chlorophyll, but it's hidden and not as effective as when it appears to be green.

Avoid overhead night watering, space plants for good air circulation, grow rust-resistant plants, be vigilant about watching imported plants and cuttings for symptoms because symptoms may appear later than when first planted, and rotate crops that are vulnerable to rust fungi.

Spraying with products containing Mancozeb or Triforine may help, but it won't eliminate the disease. Sulfur powder stops germination of rust, and some folks claim spraying a tea made of compost also helps control this disease.

Since many rusts are host-specific, plant rotation may help eliminate that disease. This fungus is a parasite that requires a living host (or two unrelated hosts) for completion of its life cycle. Spores may be spread by wind, water or insects. In the case of cedar-apple rust, the primary host is cedar, the secondary host is apple, pear or hawthorn.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

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