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Garden Pests Field Guide

Identify, understand, and control common garden pests using organic methods. Know your enemies — and your allies.

30 Common Garden Pests

1. Aphids

ID: Tiny (1–3mm), soft-bodied, pear-shaped insects in green, black, white, yellow, or woolly white. Found clustered on new growth, undersides of leaves, and stems. Often attended by ants.

Damage: Suck plant sap; cause curled, distorted, or yellowing leaves. Secrete honeydew that promotes black sooty mold. Transmit plant viruses.

Organic controls: - Strong blast of water from a hose knocks them off and most don't return - Insecticidal soap spray (2 tsp dish soap per quart water) on contact - Neem oil spray - Release ladybugs and parasitic wasps (they naturally control aphid populations) - Companion plant with nasturtiums as a trap crop

2. Slugs & Snails

ID: Slugs: gray-brown legless mollusks, 1–4 inches. Snails: same but with coiled shell. Both leave a shiny slime trail.

Damage: Ragged holes in leaves, especially tender seedlings. Feed at night and on cloudy days. Most damaging in damp conditions.

Organic controls: - Diatomaceous earth (DE) ring around plants — refresh after rain - Copper tape barriers around raised beds - Beer traps: shallow dish buried to rim, filled with beer — attracts and drowns them - Hand-pick at night with a flashlight - Iron phosphate baits (Sluggo) — safe for pets and wildlife - Remove mulch and debris where they hide during the day

3. Japanese Beetle (Popillia japonica)

ID: 1/2 inch long, metallic green with copper-brown wing covers. White tufts along sides of abdomen. Adults skeletonize leaves; grubs are C-shaped white larvae in soil.

Damage: Adults feed in groups, skeletonizing leaves from above; prefer roses, grapes, beans, and fruit trees. Grubs eat grass roots, causing brown patches.

Organic controls: - Hand-pick adults into soapy water (best done in cool morning when they're sluggish) - Milky spore disease (Bacillus popilliae) applied to lawn to kill grubs — long-term effect - Beneficial nematodes (Steinernema or Heterorhabditis) for grub control - Row covers to protect plants during peak emergence (June–August) - Avoid Japanese beetle traps — they attract more beetles than they catch

4. Tomato Hornworm (Manduca quinquemaculata)

ID: Large (up to 4 inches), bright green caterpillar with white diagonal stripes and a red or black horn on the tail. Can be hard to spot against foliage.

Damage: Devours tomato, pepper, eggplant, and potato leaves; may eat fruit. Defoliation can be rapid.

Organic controls: - Hand-pick — check undersides of leaves; drop in soapy water - If you see white cocoons on the caterpillar's back, leave it — braconid wasp larvae are parasitizing it - Bacillus thuringiensis (Bt) spray — kills caterpillars that eat treated leaves - Rotate crops to reduce soil-based egg overwintering - Till soil in fall to expose pupae to birds

5. Whitefly

ID: Tiny (1mm), white, moth-like insects. Cloud out when plant is disturbed. Found on leaf undersides.

Damage: Suck sap, weaken plants; excrete honeydew promoting sooty mold; transmit plant viruses.

Organic controls: - Yellow sticky traps to monitor and reduce adults - Insecticidal soap or neem oil — must contact insects directly - Strong water spray to dislodge nymphs - Reflective mulch confuses and repels adults - Encourage natural predators: parasitic wasps (Encarsia formosa), ladybugs

6. Spider Mites

ID: Barely visible (0.5mm), red, yellow, or green. Identified by fine webbing on leaf undersides. Populations explode in hot, dry conditions.

Damage: Stippled, bronze, or silvery appearance on leaves as cells are punctured. Severe infestations defoliate plants.

Organic controls: - Increase humidity; spider mites hate moisture - Strong water spray daily for one week - Insecticidal soap or neem oil (multiple applications, 5–7 days apart) - Predatory mites (Phytoseiulus persimilis) for greenhouse use - Avoid broad-spectrum pesticides that kill their natural predators

7. Squash Vine Borer (Melittia cucurbitae)

ID: Adult is a day-flying clearwing moth with red abdomen. Larva: white caterpillar inside squash stems. Entry point shows frass (sawdust-like excrement).

Damage: Larvae bore into and hollow out squash, zucchini, and pumpkin stems; plants wilt and die suddenly.

Organic controls: - Row covers until blossoms open (must remove for pollination) - Wrap stem base in aluminum foil — deters egg laying - Inject Bt into stems at first wilt sign using syringe - Slit stem, remove larvae, bury stem to promote rooting above wound - Plant resistant varieties (butternut squash less preferred than zucchini)

8. Cabbage Looper (Trichoplusia ni)

ID: Pale green caterpillar (1–1.5 inches) that loops its body as it crawls. Eggs: tiny, round, white domes on leaves.

Damage: Ragged holes in cabbage, broccoli, kale, Brussels sprouts leaves. Frass on leaves.

Organic controls: - Hand-pick eggs and caterpillars - Bt spray on affected plants - Row covers to prevent moth from laying eggs - Parasitic wasps control populations naturally

9. Cutworms

ID: Fat, gray or brown caterpillars, 1–2 inches. Curl into a C-shape when disturbed. Live in soil; feed at night.

Damage: Cut seedlings off at soil level overnight — classic sign is healthy seedlings toppled by morning.

Organic controls: - Cutworm collars: 3-inch sections of cardboard toilet paper rolls or plastic cups (bottom cut off) placed around stems at transplant time, pushed 1 inch into soil - Beneficial nematodes applied to moist soil - Diatomaceous earth worked into soil surface - Till soil before planting to expose and kill pupae

10. Earwigs

ID: Slender, reddish-brown, 1 inch, with distinctive pincers at the tail. Nocturnal.

Damage: Ragged holes in soft leaves, flowers, and seedlings. Also eat decaying matter and other insects (so they're somewhat beneficial).

Organic controls: - Rolled newspaper or cardboard tube traps: leave out overnight, collect in morning and shake into soapy water - Eliminate moisture and debris where they hide - Diatomaceous earth around seedlings - Low populations can be tolerated — they also eat other pests

11. Flea Beetles

ID: Tiny (1–2mm), shiny black or bronzish beetles that jump like fleas when disturbed.

Damage: Tiny, shothole-pattern holes in leaves of eggplant, tomato, brassicas. Seedlings most vulnerable.

Organic controls: - Row covers on seedlings - Sticky yellow traps - Diatomaceous earth around plants - Neem oil spray - Interplant with catnip or basil — repellent

12. Scale Insects

ID: Look like brown, yellow, or white bumps on stems and branches. Some covered in waxy shell. Rarely move.

Damage: Suck sap from woody stems; weaken plants; produce honeydew and sooty mold.

Organic controls: - Rub off by hand with a damp cloth or soft brush - Horticultural oil spray smothers the insects - Isopropyl alcohol on cotton swab for small infestations - Parasitic wasps and ladybugs reduce populations

13. Thrips

ID: Slender, yellowish-brown, 1mm. Leave silvery streaks or stippling on leaves. Shake a leaf over white paper — tiny insects fall off.

Damage: Feed on flowers and leaves; distort growth; transmit viruses; scar fruit.

Organic controls: - Blue or yellow sticky traps - Insecticidal soap or neem oil - Predatory mites (Amblyseius cucumeris) - Remove and destroy severely infested plant material - Keep weeds down — thrips overwinter in them

14. Leaf Miners

ID: Identified by the damage: white or pale squiggly trails inside leaves. Adult is a small fly.

Damage: Mines (tunnels) inside leaf tissue reduce photosynthesis. Rarely fatal but unsightly.

Organic controls: - Remove and destroy affected leaves - Neem oil prevents adults from laying eggs - Beneficial parasitic wasps (Diglyphus isaea) attack larvae in leaves - Avoid excessive nitrogen fertilization — lush growth attracts them

15. Mealybugs

ID: White, cottony masses on stems, leaf joints, and roots. The insects inside are soft, oval.

Damage: Suck sap; excrete honeydew; promote sooty mold. Common on houseplants, citrus, grapes.

Organic controls: - Dab with isopropyl alcohol on cotton swab - Spray with insecticidal soap or neem oil — multiple applications needed - Rinse plant thoroughly under water - Introduce mealybug destroyers (Cryptolaemus montrouzieri ladybug)

16. Wireworms

ID: Slender, shiny, yellow-brown larvae (0.5–1.5 inches) of click beetles. Found in soil.

Damage: Bore into roots, tubers, and seeds. Most damaging in recently broken sod.

Organic controls: - Trap with buried potato or carrot chunks — check every few days and destroy - Beneficial nematodes applied to moist soil - Allow soil to dry between watering — wireworms prefer moisture - Rotation away from grass roots (their preferred host)

17. Corn Earworm / Tomato Fruitworm (Helicoverpa zea)

ID: Caterpillar varies from green to brown with stripes. Found inside corn ears and tomatoes.

Damage: Bores into corn tips and tomato fruit; secondary rot follows.

Organic controls: - Apply vegetable oil or mineral oil droplets into corn silk tips at pollination - Bt spray on corn silk before it browns - Pheromone traps to monitor adult moth activity

18. Asparagus Beetle (Crioceris asparagi)

ID: Metallic blue-black with cream spots (spotted) or red with black stripe (common). Small, 6–9mm.

Damage: Defoliate asparagus fronds; scar emerging spears reducing marketability.

Organic controls: - Hand-pick adults, larvae, and eggs (grey-black specks on fronds) - Neem oil spray - Allow chickens to forage in established beds - Parasitic wasps naturally control populations

19. Stink Bugs (Halyomorpha halys — Brown Marmorated)

ID: Shield-shaped, mottled brown-gray, 5/8 inch. Distinctive odor when disturbed.

Damage: Puncture fruit, vegetables, and ornamentals; cause corky, scarred patches in fruit. Increasing invasive pest.

Organic controls: - Hand-pick into soapy water (don't crush — releases odor) - Kaolin clay applied to fruit and leaves as repellent coating - Row covers on fruiting crops - Trap crops: mustard, sunflower placed at garden perimeter

20. Root Aphids

ID: White to cream, waxy-coated aphids on roots; often attended by ants. Plant wilts and fails to thrive despite adequate water.

Damage: Suck roots; plants show nutrient deficiency symptoms despite good soil.

Organic controls: - Drench roots with neem oil or insecticidal soap solution - Beneficial nematodes - Remove severely affected plants to prevent spread - Avoid overwatering — stresses plants and attracts root aphids

21. Leafhoppers

ID: Wedge-shaped, 3–4mm, green or brown; hop sideways when disturbed.

Damage: Stippled leaves with white or yellow flecking; transmit viruses.

Organic controls: - Reflective mulch - Row covers on young plants - Insecticidal soap - Encourage natural predators (parasitic wasps, spiders)

22. Pillbugs / Sowbugs (Armadillidium vulgare)

ID: Gray, segmented, can roll into a ball (pillbug) or cannot (sowbug). About 1/2 inch.

Damage: Primarily decomposers; can damage seedling stems and soft fruit resting on moist soil.

Organic controls: - Reduce mulch and debris near seedlings - Elevate fruit off soil with straw or boards - Diatomaceous earth at soil level - Allow soil to dry between watering

23. Borers (Squash, Iris, European Corn Borer)

ID: Various; damage from inside stems is the key sign. Look for entry holes with frass.

Damage: Internal feeding collapses or kills stems.

Organic controls: - Prevention with row covers - Bt injection into stems - Remove and destroy infested plant material - Rotate crops annually

24. Caterpillars (Various — Imported Cabbageworm, etc.)

ID: Pale green, 1–2 inches. White butterfly adults. Eggs: yellow cones on leaf undersides.

Damage: Skeletonize brassica leaves.

Organic controls: - Hand-pick eggs and caterpillars - Bt spray - Row covers from transplant - Plant nasturtiums as a trap crop

25. Grasshoppers

ID: Familiar large insects; green, brown, or gray. Highly mobile and difficult to stop.

Damage: Chew large portions of leaves; can devastate crops in outbreak years.

Organic controls: - Nosema locustae (biological control — protozoan) applied to borders - Attract birds (guinea fowl, chickens near garden) - Row covers for valuable crops - Kaolin clay makes leaves unappealing

26. Cucumber Beetle (Spotted and Striped)

ID: Yellow-green with black spots (spotted) or three black stripes (striped). 1/4 inch.

Damage: Feed on cucurbit flowers and foliage; transmit bacterial wilt and cucumber mosaic virus — the disease transmission is often more damaging than the feeding.

Organic controls: - Row covers until blossoms open - Kaolin clay on plants - Plant resistant cucumber varieties - Trap crop: Blue Hubbard squash at perimeter

27. Carrot Rust Fly (Psila rosae)

ID: Small, shiny black fly. Damage is seen: orange tunnels in carrot roots.

Damage: Larvae tunnel into carrot, parsley, and celery roots; predisposes roots to rot.

Organic controls: - Row covers from seeding through harvest - Delay planting until late spring (after first egg-laying peak) - Harvest promptly — do not leave roots in ground too long - Rotate carrots annually

28. Scales (Soft and Armored)

ID: Appear as waxy or scaly bumps on bark and leaves.

Damage: Sap feeding weakens trees and shrubs; honeydew and sooty mold follow.

Organic controls: - Horticultural oil dormant spray on overwintering eggs - Summer oil sprays on active crawlers - Scrub with brush + soapy water for accessible infestations

29. Fungus Gnats

ID: Tiny black gnats hovering around soil. Larvae: white, transparent, in top 2–3 inches of soil.

Damage: Larvae damage fine roots of seedlings and houseplants; adults are mainly annoying.

Organic controls: - Let soil dry thoroughly between waterings — larvae need moisture - Yellow sticky traps for adults - Top-dress with sand — larvae avoid laying eggs in dry sand - Beneficial nematodes (Steinernema feltiae) drenched into soil - Bt israelensis (Gnatrol) soil drench

30. Cabbage Root Fly (Delia radicum)

ID: Fly looks like a small housefly. Larvae: white maggots at base of brassica stems.

Damage: Plants wilt from root damage; seedlings may die; crops from kale to radishes affected.

Organic controls: - Brassica collars (cardboard discs around stem base) prevent egg laying at soil surface - Row covers from transplant - Beneficial nematodes in soil - Rotate brassicas annually

20 Beneficial Insects to Attract

Your best allies in the garden. Attract them with diverse flowering plants, avoid broad-spectrum pesticides, and provide water sources.

Predators

  1. Ladybug (Ladybird Beetle) — Adults and larvae eat aphids, scale, whitefly, mites. Attract with dill, fennel, yarrow, and marigolds.
  2. Lacewing — Larvae are fierce predators called "aphid lions." Eat aphids, thrips, mites, whitefly eggs. Attract with carrot family flowers (dill, fennel, cilantro).
  3. Ground Beetle — Nocturnal hunters that eat slugs, soil-dwelling pests, caterpillar eggs. Provide mulch, stones, and logs for daytime shelter.
  4. Soldier Beetle — Eat aphids and other soft insects while also pollinating flowers. Attracted to goldenrod, marigolds, catnip.
  5. Spiders — All species. Consume enormous quantities of garden pests. Encourage by leaving some leaf litter and avoiding pesticides.
  6. Predatory Mites — Phytoseiulus persimilis hunts spider mites specifically. Thrive in humid conditions.
  7. Minute Pirate Bug — Tiny but aggressive predator of thrips, spider mites, aphids, and whitefly nymphs. Attracted to dill, fennel, goldenrod.
  8. Assassin Bug — Stabs and liquefies many garden pests. Encourage with diverse plantings.
  9. Damsel Bug — Eats aphids, small caterpillars, and leafhoppers. Attracted to carrot family plants.
  10. Robber Fly — Large, aggressive flies that catch other insects mid-flight. Leave some bare patches of sandy soil for nesting.

Parasitoids

  1. Braconid Wasps — Tiny wasps that lay eggs inside caterpillars and aphids. White rice-grain cocoons on hornworms are their larvae. Attract with small-flowered plants like alyssum, dill, and fennel.
  2. Ichneumon Wasps — Parasitize a wide range of caterpillars and beetles. Long ovipositor (egg-laying tube) visible in larger species.
  3. Trichogramma Wasps — Microscopic wasps that parasitize moth and butterfly eggs before they hatch. Commercially available; attract with small flowers.
  4. Chalcid Wasps — Parasitize whitefly, scale, and other pests. Tiny; attracted to carrot family blooms.
  5. Tachinid Flies — Look like houseflies but parasitize caterpillars, beetles, and stink bugs. Attracted to carrot family and composites.

Pollinators (Pest Allies via Diversity)

  1. Bumblebee — Also consume thrips incidentally. Essential pollinators that support diverse plantings that harbor all beneficials.
  2. Hover Fly (Syrphid Fly) — Adults pollinate; larvae eat aphids. Look like small bees or wasps. Attracted to alyssum, phacelia, and marigolds.
  3. Mason Bee — Excellent early-season pollinator. Provide hollow-stemmed plants and bee hotels.
  4. Ground-nesting Bees — Many solitary native bees nest in bare soil; avoid tilling all areas.

Decomposers That Help

  1. Rove Beetle — Ground-level hunter of fungus gnats, springtails, and root maggots. Benefits from mulch and compost.

Attracting Beneficial Insects

Plant these as habitat and food sources:

Plant Benefits
Dill Braconid wasps, lacewings, hover flies
Fennel Same as dill; also predatory wasps
Cilantro (let bolt) Parasitic wasps, hover flies
Sweet alyssum Hover flies, parasitic wasps
Phacelia Hover flies, bees
Yarrow Ladybugs, lacewings, parasitic wasps
Marigolds (single-flower) Hover flies, lacewings
Goldenrod Soldier beetles, parasitic wasps
Borage Bees, generalist beneficials
Native asters Late-season predatory wasps and beetles

Habitat tips: - Leave some bare soil for ground-nesting bees - Provide water (shallow dish with pebbles) - Leave plant stalks standing over winter — they're habitat for overwintering beneficials - Eliminate or minimize pesticide use — even organic pesticides harm beneficials - Create diversity: monocultures have few beneficials

Remember: Most insects in your garden are neutral or beneficial. The true pests are a small minority. A healthy, diverse garden creates its own balance.