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13 Common Pests of Leafy Vegetables: Photos, Prevention, and Control

Updated on July 12, 2017
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Januaris is a part-time gardener and author of farming guides. He loves to write about crops, pest control, fish farming, and beekeeping.

Garden pests can cause huge damage to leafy vegetables. If they are not well controlled or managed, they can greatly reduce the leaf quality or even kill the whole crop.

Just in case you didn't know, leafy vegetables refer to crops in the Cruciferae or Brassicaceae family. Examples of them include collard green, kale, cabbage, spinach, broccoli, rape, cauliflower, lettuce, celery, and turnip.

There are several pests that attack leafy vegetables, and all can be categorized into flies, bugs, mites, worms, and mollusks. If you grow greens or planning to grow them, here are the most common pests of leaf vegetables, their prevention, control, and management. See clear photos of these harmful organisms to help identify the exact pest affecting your crop!

The Common Garden Pests of Leafy Greens, In Brief

  1. Leaf miners
  2. Aphids
  3. Thrips
  4. Cutworms
  5. Armyworms
  6. Cabbage looper
  7. Beetles
  8. Earworms and hornworms
  9. Green vegetable bugs
  10. Spider mites
  11. Stem borers
  12. Root-knot nematodes
  13. Snails and slugs

1. Leaf Miners

Leaf miners are destructive pests that suck sap and feed on the leaves, causing white tunnels or trails on the crop. The adult insect is a grey or white fly while the larva or maggot is a greenish yellow caterpillar with a pair of black mouth hooks. It is well known to cause great damage to beet, spinach, and chard.

These harmful insects can be controlled by a suitable insecticide. They can also be controlled by biological sprays, wasp predators which eat the larva and mechanical methods such as destroying infested crops and eliminating weeds.

leaf miner causing a tunnel and trail
leaf miner causing a tunnel and trail | Source

2. Aphids

There are several species of aphids that attack greens, but the most common ones are peach aphids and potato aphids. These insects are usually small, pear-shaped with long sucking mouth parts and green, pink, orange, or dark red in color. They suck sap from the leaves and stems causing leaf cupping/curling and stunted plant growth. They can also transmit diseases such as mosaic and sooty mold.

Popularly known as plant lice, aphids can be controlled by a broad-spectrum pesticide which can be sprayed on the stems and on both sides of the leaves. However, aphids and other garden pests have become resistant to many broad-spectrum insecticides, pesticides and other killer chemicals which means that most chemicals out there do not help with these harmful organisms. When looking for the most effective pesticide, you should go for the EcoSMART Organic Garden Insect Killer which is well known to kill and repel all kinds of garden pests, including their larvae and eggs.

This ready-to-use insecticide is made of natural oils and other 100% food grade ingredients which make it safe to people, animals, and birds. The dual-action formula is also quite suitable for pest control in fruit plants, flower plants, ornamental plants, hedges, and shrubs. In addition, it comes with a trigger sprayer and in different sizes to allow you choose a size that is enough for your crops.

Aphids can also be controlled by biological methods such as beneficial parasites. For instance, ladybugs, brown lacewings, and aphidius feed on aphids and can therefore be used to control these soft-bodied bugs.

aphids attack on a leaf
aphids attack on a leaf | Source

3. Thrips

Thrips are minute winged insects that feed on the leaves and flowers causing tiny spots, lesions, and downward leaf curling. They multiply faster and kill crops within two weeks if they are not well controlled. The light green, yellow, or black insects move in large numbers and can cause heavy damage to vegetable gardens.

There are a number of ways to control thrips, including the use of pesticides, garlic fire sprays, and predators such as mites and lacewing larva. Some mechanical methods such as weed control and intercropping can also help manage these garden pests.

thrips feeding on a leaf
thrips feeding on a leaf | Source

4. Cutworms

Cutworms are more destructive in their larval form, and as their name suggests, they cut the stems and leaves of seedlings and soft crops. The adult cutworms are large-bodied, dark moths with grey wings. There are three types of the larva, black, granulate, and variegated, and all feed on the leaves, stems, and roots.

The pests can be killed by a suitable insecticide which can be applied after the worms appear in the garden. They can also be killed by parasitic wasps and flies, ground beetles, and beneficial viruses and fungi. In addition, they can be controlled by practices such as weed control, debris removal, and late planting.

cutworm
cutworm | Source

5. Armyworms

The most common vegetable armyworms are beet and southern armyworms, and both are moths in their adult form. The moths are brownish-gray and damage vegetables through laying eggs on the flowers and leaves. The larva is more destructive: it bores holes on the crop crown and feeds on the plant tissue.

Armyworms can be treated with insecticides which are available for foliar applications. They can also be controlled by worm predators, parasitoids, and beneficial microbes. In addition, they can be managed through weed control and destruction of crop residue.

armyworm
armyworm | Source

6. Cabbage Looper

As the name suggests, this pest attacks cabbage but it can be found on other greens such as broccoli, kale, turnip, mustard, cauliflower, and Brussels sprout. It is tiny and light green with silver markings or ridges and makes a loop when moving because it has only two pairs of legs. It affects crops in the larval form (caterpillar or grub) and also in the adult form (butterfly). It feeds on the leaves, causing ragged holes and other damages that lead to the loss of the crop.

Cabbage looper can be managed with pesticides, worm predators and beneficial viruses, and bacteria. It can also be managed by mechanical and physical methods such as crop rotation, squashing the butterfly eggs, and picking off the caterpillars. Concerning crop rotation, introducing lettuce after cabbage can eliminate the pest from the garden.

cabbage looper
cabbage looper | Source

7. Beetles

The most common beetles in vegetable gardens are cucumber beetles, seedcorn beetles, click beetles, and flea beetles. The cucumber beetles are small, oval-shaped and have yellow or green thorax and abdomen. The seedcorn beetles are dark brown with light colored bands on the wings. The click beetles, also known as wireworms, are dark brown and have short hairs and a large tooth-like projection. The flea beetles are tiny, dark and make flea-like movements and feed on the leaves causing holes and patches.

These harmful insects attack almost all parts of vegetable crops, including the roots and crowns, and can spread diseases such as bacterial wilt and mosaic virus. They are well known to cause notched leaves, irregular patches, and window panning on the leaves.

Concerning control, the four beetles can be killed with botanical insecticides which can be applied after the pests have been identified. They can also be controlled through crop rotation, early planting, weed control, flood irrigation, and introducing predators such as birds, spider preys, and ladybugs.

seedcorn beetles causing patches on a leaf
seedcorn beetles causing patches on a leaf | Source

8. Earworms and Hornworms

Earworms are pinkish-brown or greenish-brown caterpillars with microspines all over their bodies. On the other hand, hornworms are green and have a hornlike projection on their back end. The two caterpillars feed on the leaves and bore the stems causing great damage to the crops.

The worms can be controlled effectively by pesticides which need to be applied frequently as the pests operate outside the crop and deep in the crown. They can also be controlled through destruction of crop residues and use of predators, parasitoids, and beneficial microorganisms.

Concerning the pesticides, garden worms exhibit different behavioral characteristics which protect them from most of these killer chemicals. So you should go for a chemical that's formulated to kill the organisms even when they are exhibiting the most protective behavior.

I can only recommend one worm killer which has shown to be highly effective in my garden. This is the Safer Brand Garden Spray which targets and kills caterpillars (earworm, hornworm, armyworm, cutworm, loopers, stem borers, etc) and adult forms of insects and arachnids such as whiteflies, crickets, bugs, mites, scale crawlers, and earwings. It is just good for all garden pests, but more suitable for the larvae which are worms and caterpillars.

This worm killer is made of sulfur, insect-killing soap and potassium salts which are not harmful to people, pets, and wildlife. The 3-in-1 substance is formulated to kill the harmful organisms, prevent fungi and saturate foliage. In addition to being used in leafy vegetables, the pesticide can be used in flowers, fruits, trees, and shrubs. It is ready to use and comes with its own sprayer.

earworm causing holes on a foliage
earworm causing holes on a foliage

9. Green Vegetable Bugs

The most common vegetable bugs are the mealy, squash, and stink bugs. The three pests are well known to pierce the stems and leaves and suck the sap, causing crop distortion and stunted growth. They are pale pink, grey or white and popular in sheltered gardens.

These bugs can be controlled by natural sprays such as garlic fire and predators such as wasps. They can also be managed by methylated spirits, smothering oils, and physical methods such as squeezing and crushing with hand.

squash bug
squash bug | Source

10. Spider Mites

Spider mites are two-spotted arachnids that change color from pale green to orange or red when the weather becomes cold. They suck chlorophyll from the leaves, causing white translucent spots and a silky web that can cover the whole crop.

The garden pests can be controlled by natural predators such as beneficial mites, ladybugs, lacewings, parasitic wasps, and spiders. They can also be eradicated by an organic spray which needs to be applied on a weekly basis.

spider mites
spider mites | Source

11. Stem Borers

As the name suggests, stem borers penetrate the stems and feed on the stem tissue causing sudden wilting of the crop. The most common borers in vegetable gardens are the squash vine borer and European corn borer. The vine borers are cream-colored while the corn borers are light pink or gray with raised, dark spots all over their bodies.

Stem borers can be eliminated by pesticide sprays and practices such as removing and destroying the affected crop and clearing weed debris. They can also be managed by beneficial insects such as parasitic wasps, lady beetles, and lacewings.

european corn borer on a vegetable stem
european corn borer on a vegetable stem | Source

12. Root-Knot Nematodes

Root-node nematodes are microscopic worms that feed on the plant roots. They cause root-knot galls which prevent the roots from absorbing enough water and nutrients. With time, the affected crop withers and dies as a result of lack of water and nutrients.

These parasitic worms can be controlled with chemicals such as nematicides and fumigants. They can also be controlled through crop rotation, raising pH, heating soil, and abandoning the affected garden for some time (shifting cultivation).

root-knot galls caused by nematodes
root-knot galls caused by nematodes | Source

13. Snails and Slugs

These are soft-bodied creatures that feed on the foliage and stems. They can really cause great damage to the seedlings and tender crops. Snails have a shell on their dorsal side while slugs lack it.

The mollusks can be controlled by baits, traps, barriers, and repellants. They can also be controlled by planting resistant crops alongside the vegetables, changing cultivation methods, manual picking, and introducing predators such as chicken, salamanders, and newts. In addition, they can be managed by killer chemicals and pesticides.

snail feeding on a kale leaf
snail feeding on a kale leaf | Source

Conclusion

Leafy vegetable pests are quite many, but these are the most common ones. You can easily prevent, control, and manage these harmful organisms with the substances, practices, tasks, and methods discussed in this article. If there is a crop pest that you can’t control or manage, you can get assistance from an entomologist, pestologist, or agricultural extension officer.

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© 2017 Januaris Saint Fores

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