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Protect tomatoes from these 4 common pests

Jessica Walliser
| Sunday, Aug. 5, 2018, 12:03 a.m.

Tomatoes are arguably America’s number one backyard garden crop. But, they aren’t without their share of problems, especially in the summertime, when pest issues can play a role in affecting fruit production and quality. Though, tomatoes don’t have a huge number of pests affecting them, there are a handful that can cause big trouble. Here are four of the most common tomato pests here in Pennsylvania and how to tackle them without reaching for a spray can.

1. Tomato and tobacco hornworms. These two closely-related caterpillar species are the larvae of large, nocturnal moths known as hawk moths. Though these caterpillars start small, they can quickly reach the size of your thumb as they defoliate tomato plants from the top down. The medium green shade of hornworms means they’re well camouflaged and difficult to spot. Look for missing leaves or dark pellets of excrement on tomato foliage. Once you find this evidence, search along leaf midribs and stems for the caterpillars themselves. Since the caterpillars feed at night, these are common resting places for them during the day.

To control hornworms, simply handpick the caterpillars and toss them into a jar of soapy water or squish them. However, there’s a tiny, non-stinging species of parasitic wasp, called the cotesia wasp, that uses hornworms as hosts for their developing young. If you spy rice-like cocoons hanging off the back of the hornworm, please let it be. These very beneficial wasps will soon produce another generation and go on to control future hornworms, too. Once parasitized, the hornworms stop feeding and will soon die.

2. Aphids. These tiny, pear-shaped insects gather in groups on new foliage and leaf undersides, sucking plant sap and sometimes causing leaf deformation. Though it would take a large infestation of aphids to negatively affect the health of a full-grown tomato plant, they can damage young plants early in the season.

When you spy clusters of aphids on a tomato plant, watch them carefully. Within a few days, ladybugs, lacewings, aphidius wasps, and other beneficial insects usually arrive to naturally control aphid populations. But, if the aphids continue to reproduce uninhibited, simply squish the aphids with your fingers or collect them on the sticky side of a piece of duct tape. You can also squirt them off the plant with a sharp stream of water from the hose, knocking them to the ground where spiders, big-eyed bugs, and other ground-dwelling predatory insects will quickly find them.

3. Slugs. Finding slime trails and chewed holes in near-ripe tomatoes is often indicative of slug damage. These slimy, land-dwelling mollusks love to enjoy tomatoes the night before you’re ready to pick them! To limit slug damage on tomatoes, sprinkle an iron phosphate-based slug bait around the plants, or surround the base of the plant with a ring of copper tape. Slugs are mildly shocked when they come in contact with copper and, as a result, they avoid it. Also, since slugs are most active in wet conditions, be sure to water in the morning so the plants have time to dry off before night fall.

4. Tomato fruit worms. These caterpillars are also called corn earworms when their host plant is corn. But, when they’re found feeding on tomato fruits, they’re known as tomato fruit worms. The adults are dark brown or olive green nocturnal moths while the caterpillars can be green, yellow, or even pink, with a cream, yellow or black stripe down their sides.

Evidence of these little buggers includes perfect, round holes in ripe or unripe tomatoes. When the damaged fruit is cracked open, the caterpillar is often found inside. To control tomato fruit worms, remove and discard of damaged fruits immediately. If you know that tomato fruit worms are present in your garden, cover the developing fruits with nylon footies until harvest to prevent the female moths from laying eggs on the fruits.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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