Lauterbach: Betcha can't see just one - thrips, that is.

Special to the Idaho StatesmanMay 3, 2013 

FREE AT THE GARDEN: Check out the Idaho Botanical Garden for free, from 9 a.m. to dusk May 10 as part of National Public Gardens Day. Free tours will be held throughout the day, environmental educational partners will be at the garden, along with food trucks and Indian Creek Winery. The garden is at 2355 N. Penitentiary Road, Boise; 343-8649, ­

Thrips are so tiny you really can't see just the one unless you have a magnifying glass in hand and know what you're looking for. They're less than one- twentieth of an inch long, slender and have long fringes on the edges of their narrow wings if they're adults. Nymphs look nearly the same, but without wings.

Most species of thrips push into tight buds to feed or climb into furled leaves or other nooks and crannies of a plant to feed where we don't see their damage until it's extensive. Some species are beneficial.

Then damage shows up as stippled, silvered or distorted leaves and damaged terminal growth, or scarred flower petals. Although thrips do have wings, they're not good fliers, but they can ride the wind a long way. There are several species, some specializing in flowers, others on bean foliage, citrus, etc.

In numbers they can feed heavily in rosebuds, for instance, so buds fail to open into flowers, or if they do, the petals show discoloring in streaks or spots. Thrips also may carry diseases from one plant to another.

How can you tell thrips are your problem? Hold a white sheet of paper under a suspicious-looking branch and tap on the branch. Then look at tiny crawlers on the paper, preferably with a 10X hand lens. Look for black dots of excrement on the undersides of leaves.

You can trap them with yellow or blue sticky traps, but they're very hard to see on the blue traps. When you find their damage, blast them off with a strong stream of water or prune off the damaged twig and dispose of it, but don't compost it.

As usual with integrated pest management, consider whether the amount of damage is intolerable before you begin using pesticides. If you must, soap sprays or neem will kill visible thrips. If they're encased in buds, it would take a systemic insecticide to control them.


Systemic insecticides, those that are carried by a plant, shrub, vine or tree's circulatory system to all parts of the plant, are being used on the leafy greens we consume. Lettuce, spinach, kale, cabbage and other food crops are being treated with the neonicotinoid pesticide, Imidacloprid, according to Mother Earth News, the Pesticide Food Network and the Environmental Protection Agency website.

This is the substance used in the year-long pesticide control for insects on shrubs and trees suspected of killing bees. One of these pesticides may be applied up to seven days before harvest. That means that's the latest date the plant can absorb this pesticide through its roots and still be within EPA guidelines.

Is there a cumulative or combined effect of these pesticides? Nobody knows because no testing has been done. The EPA regulates most chemicals singly, so the total effect is nearly impossible to assess.

Keep in mind individual tolerances vary, and as the father of toxicology, Paracelsus, decreed, "The dose makes the poison." In other words, people may eat some amount of poisons without harm, but in larger doses it becomes toxic to that person.

The European Union regulates on the basis of a "precautionary principle." If in doubt about effect on human health, the substance is banned until proven safe. In the U.S., the EPA approves substances until they're proven harmful. Note that's the ENVIRONMENTAL Protection Agency, not the Citizens' Protection Agency.

This agency was created by President Richard Nixon in 1970 to protect human health and the environment. If you don't want to consume pesticides or feed them to your family, grow your own or buy organic foods. Those seem to be your best options, unless you can get Congress to act on behalf of humans.

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

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