Growing Tomatoes? Keep An Eye Out for These 7 Pests (2024)

Aphids (family Aphididae) are soft-bodied roundish or pear-shaped and gather in colonies on the undersides of leaves and stems.

They may be green, black, red, or yellow with a distinct pair of “tail pipe” structures on the back end. They suck plant juices and produce a sugary excretion called honeydew. Because they reproduce quickly and can have multiple generations per season, their numbers can explode within a few days.

“They may not produce noticeable damage but can transmit viruses to plants,” says Bertone.

What to do: Blast them off with a strong spray from the garden hose. Repeat every few days to reduce populations.

For persistent infestations, use insecticidal soap per label instructions.

Stink Bugs (family Pentatomidae) suck liquids from plants, typically the fruits. They have distinctive shield-shaped or oval-ish bodies that are about 3/4" long and wide with six legs, a marbled pattern on the body, and lighter-colored bands on the antennae.

“They cause bleach-like spots or starburst marks on fruit, and the flesh becomes corky underneath,” says Bertone. As you’d guess, they emit a strong odor if crushed.

What to do: Look for clusters of light green eggs on the undersides of leaves, and crush them.

If they’ve already hatched, you can try pesticides such as spinosad or neem oil but most products are not totally effective. Hand pick adults, if you can catch them before they drop to the ground, and submerse in soapy water.

More: How to Get Rid of Stink Bugs from Your Home

Fleahoppers (Microtechnites bractatus) are tiny, shiny black insects that can jump like a flea. They suck juices from leaves of plants, leaving small white spots or stipples, and they also leave dark fecal spots. They feed on many different plants and heavy infestations can cause leaf drop.

What to do: Typically, small infestations are not a problem. But if things seem to be getting out of control, treat with an insecticidal soap, according to label instructions. Make a second application a week or so later to deal with eggs that have hatched because they’re protected inside plant tissues where the insecticides don’t reach.

Hornworms (Manduca spp) are medium to large caterpillars that grow to become large sphinx moths. The tobacco hornworm (M. sexta) is the most common species on tomatoes. They’re green with white stripes and have a curved “horn” on their abdomen. They can consume large quantities of leaf material, says Bertone.

What to do: Hornworms often are attacked by beneficial parasitoid wasps, whose larvae feed on the caterpillar and eventually kill it.

If you’ve spotted a hornworm with what looks like little grains of rice on them, relocate it elsewhere in your garden because you want the wasps to hatch out to feed on other pests, says Pilarchik. If you aren’t lucky enough to have the help of these wasps, you can hand pick these slow-moving caterpillars and destroy them.

Armyworms (Spodoptera spp) are a group of small to medium-sized caterpillars that feed on a variety of plants, including tomatoes.

They have a yellow “Y” shape on their head with distinctive strips on their bodies. You’ll often notice their presence by the medium-sized fecal pellets left behind. They eat both foliage and fruits. They develop into medium-sized brown moths, says Bertone.

What to do: Spray with Bacillus thuringiensis kurstaki (Btk), a naturally occurring bacteria, or spinosad when the caterpillars are small and before they tunnel into fruit. These products must be ingested by caterpillars in order for them to work.

Thrips (family Thripidae) are tiny cigar-shaped insects about 2mm long which are found on flowers and leaves. They suck material from plant tissue and cause large white or silver patches on leaves.

In high densities, they’ll also feed on fruit. “Direct damage is common, but more importantly, they can transmit viruses to plants, including tomato spotted wilt virus (TSWV),” says Bertone. Fun aside: Thrips is both the singular and plural of this insect.

What to do: Spray with an insecticidal soap or horticultural oil. Because they’re so tiny, they can easily hide from sprays, so repeat applications will be necessary.

Spider Mites (Tetranychus urticae) are tiny arachnids, relatives of spiders, that feed on plants. They’re about 1mm long and feed in groups on the undersides of leaves, sometimes spilling over to fruit. They suck plant juices and create small stipples on leaves and fruit. Their numbers can be quite dense, says Bertone.

What to do: Use the hose to blast them off, or try an insecticidal soap or neem oil, making sure to cover them completely.

These sprays have little residual effect, so you’ll need to re-treat in 5 to 7 days. Spider mites can be persistent and often require multiple treatments, unfortunately.

Read more: How to Get Rid of Spider Mites