To a vegetable gardener, thrips infestation is more of a nuisance than a threat to your vegetables.
They are small, in fact so small you need a magnifying glass 10 to 15 power to see them.
They range in size from 1/25 to 1/8 inch in length.
Life cycle egg to adult completed in 2 weeks.
They are usually translucent white, black or yellow-brown but may have red, black or white color marking depending on the species and life stage. Some species have wings yet other species don't.
Depending on where you live or region of the country, they are also known as thunder flies, thunder bugs, storm flies or even corn lice.
Thrips emerge during the warm months and seek out host plants which include broccoli, cucumber, beans, carrot, cauliflower, cabbage, leek, melon, onions, peas, squash, garlic, turnip, and tomatoes.
Photo courtesy of Whitney Cranshaw, bugwood.org
They feed by puncturing leaves and sucking out cell material causing tiny scars on leaves called stippling. The damaged leaves may become papery and distorted, and
damage occurs more often than not before they can be seen. They are most noticeable by whitish spots or slivery spots or streaks.
Photo Courtesy Howard F Schwartz, bugwood.org
Discolored or distorted plant tissue or black specs (feces) may be clues thrips are or were present, although by the time plant damage is noticed, they have long since moved on.
Checking for thrips can best be done by shaking foliage onto a white sheet of paper. If they are present, they will fall onto the paper and can more easily be observed and identified.
Also, look for other signs of their presence such as small spots of varnish-like excrement on the leaves. The use of bright sticky traps placed amongst your vegetables is another popular method used by vegetable gardeners to spot thrips and other garden insect pests.
Of all the garden pests, I am not overly concerned about thrips damage to my vegetables. Even when I discover numerous quantities, I find little damage done to my vegetables. However, I do pay attention to these garden pests when my vegetable plants are very young i.e. when my plants are seedlings. Once they mature I find my time better spent dealing with other vegetable garden pests. But if you're concerned or overzealous about these pests, here are a few suggestions you can use.
This vegetable garden pest prefer a dry environment, so to prevent them from getting out of control, mist or gently water your vegetables regularly. I would suggest this technique is best done in the early morning to allow the sun ample time to dry your vegetable leaves. Also, spraying with spinosad (an acceptable organic product) will help in temporary reduction of their population. Apply when they are present and damage first appears. But do keep in mind unlike most garden pests the use of any organic (and I hope you practice organic gardening) or chemical insecticide is at best a temporary solution. Rarely do they present a danger to your vegetables health once your plants are past the seedling stage.
As with most garden pests, remove any weeds or plant debris near your vegetable garden. That also includes landscape, brush, or even flowers. I achieve this by creating what I call a "no zone perimeter" from the rest of my backyard where nothing grows.
Another technique that can also be used and is also effective for other garden pests is the use of floating row covers, hot caps, and reflective mulch. Any type of covering that prevents insect entry to your vegetables but allows light and air penetration can also be used. An example is the use of muslin or nylon cloth. There are also a variety of woven plastic on the market that is also quite effective. Check with your local nursery, or any garden center you frequent for more information about these products.
For more information on this bothersome garden pest, you may want to read this article from the University of California Agricultural dept.
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