Margaret Lauterbach

Garden pests come in all shapes and sizes

Margaret Lauterbach has the answer: What gardening zone are we in?

Idaho Statesman gardening columnist Margaret Lauterbach gives the definitive answer to the pesky and perennial question: Which zone are we in? Plus she has a few key pieces of advice specific to Boise gardeners.
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Idaho Statesman gardening columnist Margaret Lauterbach gives the definitive answer to the pesky and perennial question: Which zone are we in? Plus she has a few key pieces of advice specific to Boise gardeners.

Do you have an IPM program in place for your yard? IPM is the acronym for Integrated Pest Management, a low toxicity long-term plan for controlling pests. It originated as a program for agriculture, but has been adopted by other institutions such as museums, libraries and archives that may suffer damage from insect invasions.

Basically what this means for a home gardener is that, when pest damage is noticed in your yard, the first thing you should do is consider whether this damage is tolerable or whether it’s going to be too severe to live with. Using such a low toxicity plan can contribute to your good health and that of your family, save money and save the soil of your yard and our planet from unneeded poisons.

Try to check your plants every day, watching for any changes in leaf or fruit color, damage or configuration. The “pests” you are watching out for include insects, weeds, animals and even diseases. If you notice a problem, think about the location of your plant. Is it in the correct sun exposure? Is it watered appropriately? Too much water may be as destructive as too little water. Some plants such as gladiolus may bloom facing the “wrong direction” because they will bloom facing the direction from which they receive the longest period of uninterrupted sunlight. Even the shadow of a power pole can interrupt this sun exposure.

The source of the damage

If you see a problem that you suspect is caused by an animal, look for tracks. If none are obvious, sift some flour over the soil and see if there are tracks made overnight. Of course, a slime trail is a giveaway that there’s a snail or slug problem. An IPM program properly requires accurate identification of a pest before you consider control methods. If damage is caused by an insect, for instance, Bacillus thuringiensis (BT) will not control it, since it only controls pest worms and caterpillars. Similarly, pesticides intended to control insects don’t work on pest worms and caterpillars. Always read the label to see whether your pest is killed by the pesticide you’ve chosen to use.

Some pesticides are not quick killers either. Neem, for instance, is valuable as a destroyer of fungi, eggs and young insects, but it alters insect behavior so they forget to eat, and consequently die.

Round discs, nearly dime-sized, cut from the edges of leaves show cosmetic damage done by leaf cutter bees, common in the Treasure Valley because they can pollinate alfalfa. Some farmers have small roofed boxes in their fields housing bee boards, homes to these useful bees. A large jagged notch is probably damage by birds, a  1/8-to- 1/4-inch notch is damage by black vine weevils. That’s cosmetic damage, but their offspring are in the ground eating roots and they should be controlled. These larvae can demolish a large rhododendron if there are enough of them in the infestation. Those adult weevils don’t fly, they walk, so tend to remain in the same area. Beneficial nematodes can control those larvae.

Watch for droppings of caterpillars, coarse black “pepper” on low leaves, then look up to see if you can see the pest. Black banded caterpillars with yellow spots on the bands on parsley, carrots or dill will turn into black swallowtail butterflies, so you really shouldn’t kill them.

Controlling pests

The safest approach to insect control is killing each by hand, but that’s not always possible. In my opinion, the second best control is the use of biologic enemies of your pests, whether it’s a parasitic or cannibalistic attack. I haven’t seen a larva in broccoli for years, nor a tomato hornworm. What’s controlling them? Wasps that build mud or paper nests. Those wasps patrol my garden along with me, and they can spot an emerging larva easier than I. They gather newly hatched larvae to provision their egg cells. The adult wasps also eat aphids; they gobble them.

If biological controls are not available, use the least toxic commercial control possible, exactly following label directions lest you kill honeybees, the most efficient pollinators of our food supply.

Many diseases that afflict plants start with low temperatures and moisture on the leaves. You can avoid many diseases by watering in early morning so the leaves have a chance to dry out before temperatures fall after sundown, and/or mulching plants so there’s no water splashing on leaves.

If your plants succumb to the same disease two years in a row, look for resistant plants or plant something in an entirely different genus or family if you must plant at that site. Some diseases are soil-borne. Since so many home gardeners grow tomatoes, a lot of disease resistance testing has been done on tomatoes. Their seed packets tell what diseases they’re resistant to: VFN (resistant to verticillium, fusarium and nematodes), TA (resistant to tobacco mosaic virus and alternaria). The possibility of tobacco mosaic virus is one reason you should not let a cigarette or cigar smoker handle your plants. Testing costs money, so nearly all of the resistant varieties are hybrids. If you want that disease resistance and/or that tomato, you have to buy new seeds in future instead of saving your own.

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Handeen 2
A Deep Winter Greenhouse allows for year-around growing using little or no fossil fuel. Dan Handeen

I hope the severity of last winter is not what we’re in for in following years, but it could be the beginning. If you have a large lot, you may be interested in constructing a Deep Winter Greenhouse (DWG), designed to use little or no fossil fuel to allow year-round growing. Plans are online at

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