Tomato plants (Solanum lycopersicum) are prized for their crimson, juicy fruit. You're not the only one who enjoys the taste of tomatoes. Various pests may attack and feed on the tomato plant's fruit and foliage, causing leaf loss, plant stress and potential fruit loss. Protect your garden from some of the most common pests that afflict tomato plants.
Psyllids are tiny yellow or green insects that congregate on the underside of tomato leaves and inject a poison into the leaves, turning the tomato plant's foliage yellow and purple. These pests rarely reach population levels that cause true damage; most gardeners simply dislike psyllids for aesthetic reasons.
If you choose to control and eradicate psyllids, make your own psyllid insecticide at home:
Pour 1/2 ounce of liquid hand soap or liquid dish detergent into a reusable spray bottle.
Add 2 quarts of water to the spray bottle.
Spray the soapy solution onto affected portions of the tomato plant, focusing on the underside of leaves where psyllids like to gather.
Repeat once a week until psyllid activity subsides.
Flea beetles, another common tomato pest, are brown or black beetles that hop away from you when touched. The adult beetles eat small holes into the foliage of the tomato plant.
Cover the vegetable bed with a floating row cover to block out beetles and protect young tomato plants. A floating row cover is an ultralight, ultrathin landscaping sheet that keeps pests from reaching the underlying plants but still lets sunlight and water get through. Drape the row cover over the garden bed as soon as tomato seedlings emerge, and weigh down the edges of the sheet with rocks or with U-shaped garden pins.
If flea beetles have already arrived, a floating row cover will not help. Instead, dust all exposed surfaces of the tomato plants with food-grade diatomaceous earth. This all-natural powder is made from crushed diatoms. The powder's tiny, sharp edges kill flea beetles.
If you see large gray-green or green caterpillars crawling on your tomato plants, you have a tomato hornworm problem. This pest is a fast eater. In just a few days, the caterpillars can completely strip the entire tomato plant of its leaves and fruit.
Pick the hornworms off of the tomato plant by hand. This is a convenient, efficient and simple way to eradicate the problem. Crush the caterpillars or drop them into a bucket of soapy water to kill them.
If you prefer a hands-off approach, use an organic caterpillar insecticide made with Bacillus thuringiensis kurstaki. Bt is a natural bacterium that kills caterpillars when it gets ingested. Bt insecticides come in sprays and powders.
Follow all labeled guidelines for product-specific application instructions. For example, when using a Bt insecticide powder with 0.4365 percent Bt, apply at a rate of 2 ounces for every 50 feet of row planting, dusting the powder evenly on all exposed parts of the tomato plant.
Whiteflies and Aphids
Whiteflies and aphids suck on the sap of the tomato plant and can cause wilting and leaf loss. A common symptom for either pest is the presence of honeydew -- a sticky, shiny substance excreted by the insects when they're feeding.
Spray the tomato plant with a strong jet of water from a garden hose. This is often all that's required to knock the aphids and whiteflies off of the plant and kill them. Repeat once a week to keep pest populations low.
Last but not least on the tomato plant's most-wanted pest list are stink bugs. These shield-shaped beetles come in various colors, including brown and green. If touched, they let out a pungent odor, hence their name. Stink bugs feed on tomato fruits causing spotting and the inner tissue becomes spongy and white. The first sign of damage appears as tiny dark spots surrounded by discoloring that can turn yellowish or green as the fruit matures.
Handpick the stink bugs off of the tomato plant -- wear gloves if you want to avoid their trademark stench -- and crush the bugs or drop them into a bucket of soapy water. Alternatively, use a handheld vacuum to quickly suck the insects off of the affected plant. Remove the vacuum's dust bag, place it in a sealed plastic bag and toss it in your freezer for a couple days to kill the trapped stink bugs.
- Colorado State University Extension: Recognizing Tomato Problems
- University of California Integrated Pest Management Program: Psyllids
- Texas AgriLife Extension: Materials for Controlling Psyllid
- Colorado State University Extension: Flea Beetles
- University of Minnesota Extension: Tomato Hornworm
- University of California Integrated Pest Management Program: Aphids
- University of California Integrated Pest Management Program: Whiteflies
- University of California Integrated Pest Management Program: Brown Marmorated Stink Bug
- Safer: Garden Dust with B.T.
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