Kill Thrips in the Organic Garden

Organic gardeners unfamiliar with thrips might bemoan their brown thumbs when plants develop discolored leaves and fail to thrive, seemingly for no reason. Closer inspection can reveal a horde of miniscule pests belonging to the order Thysanoptera, which includes several species of garden thrips that puncture leaves and feed on the plant juices within. Gardeners must use a combination of sanitary, cultural, biological, and organic spray control methods to kill these pests and the fight the diseases they carry.

Identifying Damage from Thrips

Thrips are so tiny, approximately 1 mm in size, that organic gardeners may have difficulty identifying the pests without the aid of a magnifying glass. Instead of viewing the pests directly, you can learn to recognize signs of thrip damage. Thrips feed on vegetable and ornamental plants using a combination of sucking and rasping, which causes a distinct speckled appearance, frequently at the tips of affected plants.

Thrips enjoy feeding on beans, onions, and squash in the vegetable garden. Thrips have an affinity for bright pink and blue colors, and they gravitate towards gladiolus and petunias in the flower garden. You can place pink or blue sticky traps around susceptible plants and inspect the cards with a magnifying glass to check for thrip infestations.

Another way to identify damage from thrips is by diagnosing the diseases these garden pests carry. Western flower thrips carry tomato spotted wilt virus, as well as necrotic spot virus. There aren’t any accepted organic cures for these diseases, but you can stop these diseases from affecting your entire garden by controlling thrips. Ask your local county extension agent to help you in identifying both the winged pests and the diseases they carry.

Garden Hygiene

Strict sanitation in your garden and greenhouse can help organic gardeners control thrips. These pests love to hide out in the nooks and crannies of weeds, so deny them a safe haven by keeping your garden weed-free. You must also keep a weed-free margin of at least 10 feet around your greenhouse, especially around vents and doors.

If you’ve experienced thrips in the previous gardening season, dispose of any affected plants through your sanitation pick up service. This applies to plants affected with the wilts thrips carry, as both disease spores and thrips may survive insufficient composting temperatures.

Cultural Control

Because thrips thrive in the same hothouse atmosphere you cultivate to coddle your flowers, greenhouse infestations are particularly difficult to control. In order to avoid chemical sprays, organic gardeners must sometimes allow a fallow period in the greenhouse to regain cleanliness and order. Usually, one summer is sufficient to eliminate thrips, a time when most plants in the greenhouse appreciate an outdoor vacation. Make sure greenhouse temperatures soar to 105 degrees F or greater to eliminate thrips.

Biological Controls

If your vegetable garden suffers from thrips, you may achieve satisfactory control using predatory insects. This is because thrips feed heavily on leaves and flowers, leaving fruits relatively untouched. You can release ladybugs into your greenhouse or garden, and you can special order beneficial soil-dwelling nematodes like Heterorhabditis bacteriophorathat not only control thrips, but also feast on cutworms, grubs, and weevils.

Organically Acceptable Pesticides

When only unblemished blossoms will do, biological thrip management won’t provide the control you desire. You can use neem oil or insect soap to prevent thrips from damaging your flowering plants. You will need to treat plants repeatedly, as thrips will evade you like little martial artists, ducking and dodging under plant leaves to continue their destructive life cycle.

Source:

National Sustainable Agriculture Information Service