Monday, May 16, 2011

Thrips: Tiny Pest, Big Impact

Walking through the lawn and feel a sharp bite on your arm only to look down and see nothing? Look a little closer: that tiny beige freckle is moving! Thrips are itty, bitty winged insects that will feed on most any plant, and are happy to take a taste of you from time to time. They are easily controlled with a good balance of predatory insects like lacewings, but can kill vegetation if allowed to populate out of control. According to the Texas Organic Vegetable Gardening book (a must own for all Texas veggie gardeners) thrips
attack buds and tight-petaled flowers such as roses. They are barely visable to the naked eye but will rasp the plant tissue and drain teh sap. Heavy infestations can kill plants... Controls include seaweed, lacewings, citrus and neem.
How do you determine thrip damage? The sap suckers will leave leaves with a mottled appearance and can deform leaves and flowers. You may see runner lines on the underside of the leaves and sotty debris from their droppings. My early tomatoes had trouble setting their flowers last year: thrips were to blame. Thrips can also cause problems by spreading disease from plant to plant. If you notice a spread of wilt throughout your garden, you may have thrips to blame. This image shows thrip damage on cucumber plants:

I think i may have just determined what's plaguing this year's cucumber crop in my own garden. Here's my cucumber:

Looks pretty similar, ay? I had some weeeiiiird disease looking deformation in my cucumbers the year before last: twisted up flowers and mangled leaves. I'm thinking thrips may have been to blame then as well. I did spot some small leafhoppers on the leaves, so this damage may be due to them or a combination of the two pests. Thrips are more likely to descend effectively on your crops when they're suffering from dryness. Another reason that automated irrigation, preferable at the soil level is so important to the health of your garden. Thrips are also attracted to pink and blue, making them common pests for flowers like petunias. You can control or at least ID your problem as thrips by placing bright blue or pink cards sprayed with sticky trap at intervals in your garden. Another useful control for thrips is allowing dry, weedy areas to remain outside of your garden. The thrips like the dry, unhealthy grassy weeds (another reason you'll feel the stingy thrip bites while walking through droughty lawns) and will leave your vegetables alone.

Our massive drought is definitely taking a toll on my (unautomated) garden. Plants are stunted due to lack of consistent water, and pests are staking their claims. The natural predators usually found in force in my garden (toads, anoles and predatory insects) have been hiding from the heat themselves  and aren't doing their jobs as well as i normally expect them to! To be honest, i've just about had it with this season. I'm so happy to see some of our clients' gorgeous gardens on a weekly basis. Despite the drought, their gardens (with automated watering) are really popping and utilizing this heat and sun to set early harvests. For the rest of us struggling through the heat - it's time to start seeds for Fall. Let's hope that season does us a little more kindly.

Some very excellent photos of various species of thrips and their damage can be found on this site. Perusing this page makes me realize I have a lot more thrip damage on a lot more plants than I ever thought. Onions, citrus, cucurbits and beans all show signs of thrip damage in my garden. Dang!

Articles with useful information on thrips:
This post can also be found at Yard Farm Austin.

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