Common Garden Pests

How to Use This Guide

This guide is designed as a field reference for organic and low-spray garden management. It is organized to help you quickly identify what you're seeing and take the most effective action. Most garden pest problems are manageable with organic controls when caught early. The three most important principles in organic pest management are: (1) correct identification before taking any action; (2) early intervention when populations are small and damage is minimal; and (3) supporting natural enemies that do much of the pest control work for free.

Organization: Section 1 is a rapid symptom key — if you see damage and don't know the cause, start here. Sections 2 through 7 provide individual pest profiles organized by pest type (sucking insects, chewing insects, soil pests, caterpillars, beetles, and other pests). Section 8 covers beneficial insects that are your allies. Sections 9 and 10 provide crop-by-crop and seasonal reference tables.

Geographic scope: This guide covers pests found across the United States. Regional prevalence notes are included in each profile. Pest pressure and species composition varies by climate zone, region, and season — your state cooperative extension service can provide the most locally specific pest management guidance.

Organic Pesticide Quick Reference

Section 1: Rapid Symptom Key — Identify by What You See

Use this table when you see damage and don't immediately know the cause. Observe symptoms carefully before treating — many symptoms have multiple possible causes, and treating for the wrong pest wastes money and may harm beneficial insects.

Section 2: Sucking Insects — Aphids, Mites, Whitefly, Scale & Thrips

Sucking insects feed by inserting a piercing mouthpart (stylet) into plant tissue and withdrawing cell contents, sap, or phloem fluid. They cause stippling, distortion, yellowing, and honeydew deposition. Most sucking insects are best controlled with contact products (insecticidal soap, neem oil) that must directly contact the pest to be effective. Natural enemies (ladybugs, lacewings, parasitic wasps) are highly effective and should be protected whenever possible.

Aphids (Multiple species — family Aphididae)

• •Size: 1/16″ – 1/8″ (1–3 mm); visible to naked eye in clusters
• •Color: Green, black, yellow, pink, white, gray, or woolly white — color varies dramatically by species
• •Shape: Soft, pear-shaped body; 2 small tubes (cornicles) projecting from rear; may be winged or wingless
• •What you see: Clusters on new growth, stem tips, leaf undersides; distorted curled leaves; sticky honeydew; sooty black mold; ants tending colonies
• •Hosts: Almost all vegetables, fruits, flowers, and ornamentals — one of the broadest pest host ranges of any insect group
• •Regions: All 50 states; year-round in warm climates; spring–fall in northern states. Most problematic in spring during rapid plant growth.

• •Organic controls: (1) Strong water spray to knock off colonies — very effective; repeat every 2–3 days. (2) Insecticidal soap spray directly on aphid clusters — must contact the insect. (3) Neem oil. (4) Introduce or encourage ladybugs, lacewings, and parasitic wasps — a single ladybug larva consumes 400 aphids in its development. (5) Pyrethrin for severe infestations.
• •Natural enemies to protect: Ladybugs (adult and larvae), green lacewing larvae, parasitic wasps (Aphidius spp. — mummified brown aphids are a sign they are working), hoverfly larvae, soldier beetles
• •Cultural controls: Avoid excessive nitrogen fertilization (promotes the succulent new growth aphids prefer). Plant pest-repelling companions: nasturtium (aphid trap plant), garlic, chives, catnip near susceptible plants. Reflective mulch disorients aphids flying in from adjacent areas.

Spider Mites (Tetranychus urticae and related species)

• •Size: Microscopic — 1/50″ (0.5 mm); barely visible as moving dots to the naked eye; magnification reveals ovoid body with 4 pairs of legs
• •Color: Yellow-green with dark spots (two-spotted spider mite); red (European red mite); russet mite (microscopic)
• •Webbing: Fine silk webbing on leaf undersides, between leaves, and along stems — webbing distinguishes mites from all other pests
• •What you see: Stippled, bronzed, or silvered leaves; premature leaf drop in severe infestations; fine webbing; worst in hot, dry conditions
• •Hosts: Tomatoes, cucumbers, beans, strawberries, roses, conifers, fruit trees, houseplants — very wide host range
• •Regions: All regions; most severe in hot, dry climates (Southwest, Midwest during drought). Populations explode rapidly in heat. Indoor/greenhouse populations year-round.

• •Organic controls: (1) FIRST: strong water spray to undersides of leaves — physically removes mites and their webbing; most effective non-chemical control. (2) Increase humidity — mites thrive in dry conditions. (3) Insecticidal soap to leaf undersides — repeat every 5–7 days for 3 treatments. (4) Neem oil. (5) Predatory mites (Phytoseiulus persimilis) — available from online suppliers; excellent for greenhouse and high-value situations.
• •Natural enemies to protect: Predatory mites (Phytoseiidae family), minute pirate bugs, lacewing larvae, predatory thrips (Scolothrips spp.)
• •Cultural controls: Avoid dusty conditions (dust suppresses natural predators). Do not overfertilize with nitrogen. Maintain adequate irrigation — water-stressed plants are more susceptible. Avoid broad-spectrum insecticides that kill predatory mites.

Whitefly (Bemisia tabaci, Trialeurodes vaporariorum, and others)

• •Size: Adults 1/16″; oval yellow body with powdery white wings. Nymphs are flat, oval, scale-like, and barely visible on leaf undersides.
• •Color: Adults white; nymph instars pale yellow to transparent flat ovals on leaf undersides
• •What you see: Adults fly in white clouds when plant is disturbed; yellowing; wilting; sticky honeydew; sooty black mold; nymphs on leaf undersides
• •Hosts: Tomatoes, peppers, squash, melons, sweet potatoes, beans, cucumbers, poinsettia, many tropical ornamentals
• •Regions: Most severe in the South (Zone 7+), California, and in greenhouses nationwide. Silverleaf whitefly is a tropical species most problematic in warm climates and greenhouses. Year-round in Zone 9+.

• •Organic controls: (1) Yellow sticky traps — highly effective for monitoring and reducing adult populations; change weekly. (2) Insecticidal soap to leaf undersides — targets crawlers and nymphs; must contact directly. (3) Neem oil. (4) Spinosad. (5) Reflective silver mulch reduces whitefly landing rates significantly. (6) Pyrethrin for severe infestations in the evening.
• •Natural enemies to protect: Encarsia formosa parasitic wasp (excellent biological control; commercially available for greenhouse use); Delphastus catalinae predatory beetle; lacewings
• •Cultural controls: Remove and dispose of heavily infested leaves (do not compost). Avoid overfertilizing. Inspect and quarantine new transplants before placing near existing plants.

Mealybugs (Pseudococcus spp., Planococcus citri, and others)

• •Size: 1/16″ – 1/4″; oval, soft-bodied insects covered in a white, waxy, mealy coating
• •Color: White to gray; the waxy coating makes them appear fluffy or cottony
• •What you see: White cottony masses in leaf axils, stem joints, root crown; sticky honeydew; sooty mold; yellowing and wilting in severe infestations
• •Hosts: Citrus, grapes, succulents, cacti, orchids, houseplants, many ornamentals; outdoors in warm climates on vegetables
• •Regions: Year-round in Zone 9+; warm greenhouses and houseplant collections nationwide. Most common as an indoor/greenhouse pest in northern states.

• •Organic controls: (1) Rubbing alcohol on a cotton swab — wipe individual colonies directly; extremely effective for small infestations. (2) Insecticidal soap applied to all plant surfaces. (3) Neem oil (good residual deterrent). (4) Repeat applications weekly for 4–6 weeks — mealybugs are persistent and have protected egg stages. (5) Introduce Cryptolaemus montrouzieri (mealybug destroyer beetle) for large greenhouse infestations.
• •Natural enemies to protect: Cryptolaemus montrouzieri (mealybug destroyer ladybug); lacewing larvae; Leptomastix parasitic wasps
• •Cultural controls: Inspect new plants carefully before introducing to your collection; quarantine for 2–3 weeks. Remove ants that protect mealybugs from natural enemies. Isolate infested plants immediately.

Scale Insects (Armored scale — Diaspididae; Soft scale — Coccidae; many species)

• •Adults: Sessile (permanently attached). Armored scale: hard, removable waxy covering separate from the body. Soft scale: the body itself is the covering.
• •Crawlers: The mobile first-instar nymphs are the most vulnerable stage — tiny, flat, oval, and yellow to orange
• •What you see: Brown, tan, white, or gray bumps on stems and leaves; yellowing; honeydew and sooty mold (soft scale more than armored); plant decline
• •Hosts: Fruit trees, ornamental shrubs, houseplants, citrus, grapes, junipers, roses — heaviest on woody plants and shrubs
• •Regions: Found in all regions; most species more problematic in warm climates (Zone 7+). Significant indoor/greenhouse problem nationwide.

• •Organic controls: (1) Horticultural oil — dormant oil for dormant-season application; summer-weight oil during the growing season; highly effective by smothering overwintering eggs and crawlers. (2) Insecticidal soap on crawlers. (3) Rubbing alcohol on a toothbrush for removing scale from woody stems. (4) Neem oil.
• •Natural enemies to protect: Parasitic wasps (many species specific to scale); scale-eating ladybugs (Chilocorus spp.); predatory beetles
• •Cultural controls: Monitor for crawler emergence in spring with sticky tape wrapped around branches. Prune and dispose of severely infested branches. Maintain plant vigor — stressed plants are more susceptible.

Thrips (Frankliniella occidentalis, F. tritici, Thrips tabaci, and others)

• •Size: 1/20″ – 1/16″ (1–1.5 mm); slender, fast-moving; barely visible to naked eye; fringed wings on adults
• •Color: Yellow to brown to black; very variable by species and instar
• •What you see: Silvery scarring or streaking on leaf surfaces; distorted new growth; black fecal specks on leaves; flower petals with dark streaks or brown edges; fruit scarring
• •Hosts: Onions, beans, squash, peppers, tomatoes, cucumbers, flowers (especially roses, impatiens, gladiolus) — very wide host range
• •Regions: All regions; most severe in warm, dry conditions. Western flower thrips is the most economically important and widely distributed species. Also vectors tomato spotted wilt virus (TSWV) and impatiens necrotic spot virus (INSV).

• •Organic controls: (1) Blue or yellow sticky traps for monitoring — blue traps are more effective for thrips specifically. (2) Insecticidal soap on all plant surfaces including flowers. (3) Spinosad — the most effective organic control for thrips; apply in late afternoon after bee activity. (4) Neem oil as a deterrent. (5) Reflective mulch reduces thrips landing rates.
• •Natural enemies to protect: Minute pirate bugs (Orius spp.) — among the most effective predators; commercially available. Predatory mites (Amblyseius cucumeris). Lacewing larvae.
• •Cultural controls: Remove and dispose of heavily infested flowers and plant material. Avoid excessive nitrogen that promotes the succulent growth thrips prefer. Inspect new transplants carefully — thrips are often introduced on new plants.

Section 3: Soil Pests — Cutworms, Grubs, Wireworms & Nematodes

Soil pests damage plants at or below the soil surface, making them difficult to detect until significant damage has occurred. Prevention — physical barriers, crop rotation, beneficial nematodes, and healthy soil biology — is more reliable than treatment for most soil pests. When soil pest damage is suspected, dig around the base of affected plants to examine the root zone.

Cutworms (Agrotis ipsilon, Peridroma saucia, and others)

• •Adult: Gray-brown moths; nocturnal; non-damaging as adults
• •Larva: 1–2 inch plump caterpillars, gray to brown to nearly black; curl into a C-shape when disturbed; greasy appearance
• •What you see: Young transplants and seedlings severed at or just below soil line overnight; plants topple and wilt; the plant appears cut off cleanly
• •Hosts: Nearly any young transplant or seedling; particularly destructive on tomatoes, peppers, cabbage family, corn, and annual flowers at transplanting time
• •Regions: All 50 states; most damaging at the time of spring and fall transplanting when populations of overwintering or spring-hatched larvae are active in the soil

• •Organic controls: (1) Physical collar barriers — a 3–4 inch cylinder of cardboard, newspaper, or plastic pushed 1 inch into the soil and extending 2–3 inches above; most effective prevention. (2) Beneficial nematodes (Steinernema carpocapsae) applied to moist soil before transplanting; effective for 4–6 weeks. (3) Bt kurstaki applied to soil surface at dusk. (4) Diatomaceous earth around transplant bases. (5) Hand-pick by digging 2–3 inches below cut plants at night.
• •Natural enemies to protect: Ground beetles, tachinid flies, parasitic wasps, birds, toads
• •Cultural controls: Cultivate soil 2–3 weeks before transplanting to expose larvae to birds and weather. Remove plant debris (cutworms hide under it during the day). Check planting areas at dusk with a flashlight for active larvae.

White Grubs (Japanese Beetle, June Bug, May Beetle larvae — Popillia japonica and related scarab species)

• •Larva: 1/2″ – 1.5″ C-shaped grubs with a white or cream body, brown head capsule, and 3 pairs of true legs; found in soil, particularly in lawns
• •Adult: Beetles emerge in summer — Japanese beetle is metallic green with copper-brown wing covers (1/2″); June bugs are reddish-brown (3/4″ – 1″)
• •What you see in lawns: Irregular dead patches; sod rolls back like carpet revealing C-shaped grubs; raccoons and skunks dig up lawn
• •What you see in gardens: Roots chewed; plants wilt and die; tugging the plant reveals no root attachment
• •Hosts (larvae): Grass roots (primary); vegetable root systems; ornamental plant roots in ground
• •Regions: Japanese beetle is primarily eastern US (east of the Mississippi, expanding westward); most damaging in the Northeast and Midwest. Grub damage most visible in late summer and fall.

• •Organic controls for grubs: (1) Milky spore disease (Paenibacillus popilliae) — specific to Japanese beetle grubs; apply to lawns; takes 2–3 seasons to establish but persists for years. (2) Beneficial nematodes (Heterorhabditis bacteriophora) — apply in late summer/early fall when young grubs are near the surface; must be applied to moist soil. (3) Steinernema glaseri for larger grubs.
• •Organic controls for adult beetles: (1) Hand-pick adults into soapy water in early morning when sluggish. (2) Row cover over vulnerable plants during peak adult flight. (3) Kaolin clay deterrent. (4) Pyrethrin. AVOID Japanese beetle traps — research shows they attract more beetles than they catch and increase damage in the surrounding area.
• •Cultural controls: Reduce lawn area (primary grub habitat). Maintain healthy, deep-rooted turf. Attract and support natural predators: birds, ground beetles, parasitic wasps.

Wireworms (Agriotes spp., Melanotus spp., and other click beetle larvae)

• •Larva: 1/2″ – 1.5″ long; slender, hard-bodied, shiny, yellow-brown; cylindrical with distinct segments; live in soil 3–6+ years before pupating
• •Adult: Click beetles (1/2″ – 3/4″); not directly damaging; make a clicking sound when flipped onto their back
• •What you see: Small round holes bored into potato tubers, carrot roots, corn kernels at germination, beets; wilting seedlings with damaged roots; round tunnels through root crops
• •Hosts: Root crops (potatoes, carrots, beets, sweet potatoes, radishes); corn and small grain seedlings; transplant roots of many vegetables
• •Regions: All regions; most problematic in the Pacific Northwest, California, and in recently turned sod or fields converted from grass. Populations highest in soils with high organic matter.

• •Organic controls: (1) Beneficial nematodes (Steinernema feltiae) applied to moist soil before planting. (2) Trap crops: bury pieces of potato or carrot as bait traps; dig up and destroy weekly. (3) Diatomaceous earth incorporated into the planting area. (4) Mustard seed meal (biofumigant) incorporated into soil.
• •Cultural controls: Avoid planting root crops in areas recently converted from sod. Rotate root crops to new areas annually. Deep cultivation exposes wireworms to birds and desiccation. Allow soil to dry somewhat before planting in wireworm-prone areas.

Root-Knot Nematodes (Meloidogyne incognita, M. arenaria, M. hapla, and related species)

• •What they are: Microscopic roundworms in the soil; females induce the formation of galls (knots) on roots where they feed and lay eggs; cannot be seen without a microscope
• •What you see above ground: Plants stunted, yellowing, wilting despite adequate water — symptoms appear when plants should be vigorous
• •What you see below ground: Bumpy, knotted galls on roots — the diagnostic sign. Not the same as nitrogen-fixing nodules (which are smooth and pink).
• •Hosts: Tomatoes, peppers, cucumbers, melons, squash, beans, carrots — very wide host range; most vegetable crops are susceptible
• •Regions: Most severe in the South and Southwest (Zone 7+) where hot, sandy soils support large populations. M. hapla is the northern root-knot species, active in cooler soils. Worst in light, sandy, warm soils.

• •Organic controls: (1) French marigolds (Tagetes patula) as a dense interplanting or cover crop — roots exude compounds toxic to root-knot nematodes; plant densely and till in at season end for best effect (requires a full season). (2) Beneficial nematodes (Steinernema and Heterorhabditis spp.) have some suppressive effect. (3) Soil solarization — highly effective in summer in warm climates; reduces populations in the top 6 inches significantly. (4) Neem cake (meal remaining after oil extraction) incorporated into soil.
• •Cultural controls: Choose resistant varieties — look for N in tomato hybrid codes (VFN = Verticillium, Fusarium, Nematode resistant). Crop rotation using non-host crops (corn, onions, garlic, small grains) for 1–2 seasons. Improve soil organic matter to promote natural nematode enemies. Add compost generously.

Section 4: Caterpillars & Larvae — The Leaf & Fruit Eaters

Caterpillars are the larvae of moths and butterflies (order Lepidoptera). They are among the most damaging garden pests by volume of plant tissue consumed, but also among the most effectively managed with targeted organic controls — particularly Bt (Bacillus thuringiensis), which kills caterpillars specifically without harming other insects when used correctly.

Tomato Hornworm & Tobacco Hornworm (Manduca quinquemaculata & M. sexta)

• •Size: One of the largest garden caterpillars — 3–4 inches long when mature; green with white diagonal stripes; a horn on the rear end
• •Tomato vs. tobacco: Tomato hornworm has V-shaped white marks on its sides and a black horn. Tobacco hornworm has diagonal white stripes and a red horn. Both cause identical damage.
• •What you see: Dramatic defoliation of tomato, pepper, and eggplant; large dark green or black droppings (frass) on leaves below the feeding site; stems stripped of leaves; the green larva is extremely well-camouflaged
• •Adults: Large sphinx moths (hummingbird moths); wingspan 4–5 inches; not damaging but lay eggs on plant
• •Regions: Throughout the continental US; M. quinquemaculata more common in northern states; M. sexta more prevalent in the South. Peak caterpillar feeding in mid-to-late summer.

• •Organic controls: (1) Hand-pick — the most effective control; hornworms are large enough to find by their frass and by black-light inspection at night (they fluoresce). (2) Bt kurstaki sprayed on foliage — larvae must ingest treated foliage; most effective on young larvae. (3) Spinosad.
• •Natural enemies to protect: Cotesia congregata parasitic wasp — hornworms bearing small white cocoons on their backs are being controlled by this wasp and should not be killed; they will not survive to reproduce. Trichogramma egg parasites. Ground beetles.
• •Cultural controls: Till soil in fall to expose pupae to birds and cold. Plant dill, basil, and marigold to attract beneficial wasps. Row cover over young transplants before egg-laying period.

Imported Cabbageworm (Pieris rapae)

• •Adult: The familiar cabbage white butterfly — white wings with black-tipped forewings; adults are not damaging but lay pale yellow bullet-shaped eggs on cabbage family leaves
• •Larva: Velvety green caterpillar with a faint yellow dorsal stripe; 1–1.5 inches at maturity; very well camouflaged on green leaves
• •What you see: Ragged holes in outer leaves of cabbage, broccoli, cauliflower, kale, and brussels sprouts; green frass inside cabbage heads; frass on leaf surfaces below feeding sites
• •Hosts: All Brassica species — cabbage, broccoli, cauliflower, kale, brussels sprouts, kohlrabi, bok choy, arugula, radish, turnip
• •Regions: Throughout the US; 2–3 generations per season in most regions; most damaging in spring and fall when brassicas are in season. Year-round in mild climates.

• •Organic controls: (1) Row cover from transplanting through harvest — most effective prevention; removes the butterfly from contact with the plant entirely. (2) Bt kurstaki applied weekly when butterflies are active — must be ingested by larvae; reapply after rain. (3) Spinosad. (4) Hand-pick larvae and yellow eggs. (5) Trichogramma parasitic wasps released when adults are present.
• •Natural enemies to protect: Trichogramma parasitic wasps (attack eggs); Cotesia glomerata (larval parasitoid); spiders; ground beetles
• •Cultural controls: Inspect plants twice weekly and hand-remove eggs (pale yellow, bullet-shaped on leaf undersides). Plant purple or red cabbage varieties — some studies show they receive less egg-laying.

Squash Vine Borer (Melittia cucurbitae)

• •Adult: Day-flying moth resembling a wasp — red abdomen with black dots, metallic green wings; forewing span 1–1.5 inches; present in early summer
• •Larva: Creamy white caterpillar, 1–1.5 inches; found inside the vine stem; wrinkled body; brown head capsule
• •What you see: Sudden wilting of a mature squash vine that had appeared healthy; sawdust-like frass (orange-green) at a small entry hole on the stem base; vine yellows and dies rapidly; cutting open the stem reveals the larva inside
• •Hosts: Butternut and acorn squash (most susceptible); zucchini; pumpkins (less so); winter squash; sometimes cucumbers and melons
• •Regions: Eastern US, Midwest, and southern states; less common in the West. Most damaging from June through August. Adult flight period is 4–6 weeks.

• •Organic controls: (1) Row cover from transplanting until flowering (remove for pollination). (2) Time planting to avoid peak adult flight: in northern regions, plant zucchini in mid-June or early July so vines are small during early July peak; or plant in early spring so vines are large and past peak vulnerability. (3) Wrap stem bases with aluminum foil to deter egg-laying. (4) Inject Bt into stem at entry holes. (5) Cut out larvae with a knife and bury the vine node in soil — it may root and continue producing.
• •Natural enemies to protect: Parasitic wasps attack eggs; spiders; predatory wasps
• •Cultural controls: Monitor for orange, flat eggs on stem bases from June onward. Grow resistant varieties (butternut is more resistant than acorn). Remove and destroy infested vines promptly to prevent larvae from completing development.

Corn Earworm / Tomato Fruitworm (Helicoverpa zea)

• •Larva: 1.5–2 inches; highly variable in color — green, brown, pink, or nearly black with pale stripes; spiny head capsule visible with a hand lens
• •What you see on corn: Silks eaten; tip of ear shows frass and feeding; larva in tip of ear when husked; chewed kernels at the ear tip
• •What you see on tomato: Entry hole in fruit near the stem scar area; frass at entry hole; hollow cavity inside fruit; larva inside
• •Hosts: Corn (primary); tomatoes, peppers, beans, squash, sorghum; broad host range late in season
• •Regions: Throughout the US; a major economic pest. Overwinters in the deep South and migrates northward on storm fronts each spring. Northern regions see 1–2 generations; southern regions 3–4+ per year.

• •Organic controls on corn: (1) Apply a few drops of mineral oil to each silk mass 3–4 days after silk emergence — prevents larvae from entering the ear. (2) Inject Bt into each ear at silk stage every 3–5 days. (3) Spinosad timed to silk emergence. (4) Trichogramma egg wasps released at tasseling.
• •Organic controls on tomato: (1) Bt or spinosad applied when adult moths are flying (use pheromone traps to monitor flight). (2) Pyrethrin. (3) Remove and dispose of infested fruit immediately.
• •Natural enemies to protect: Trichogramma parasitic wasps; Cotesia marginiventris; earwigs (predators of eggs and young larvae); ground beetles

Cabbage Looper (Trichoplusia ni)

• •Adult: Brown moth with a silver figure-eight marking on each forewing; nocturnal; flies spring through fall
• •Larva: 1.5–2 inches; pale green; moves in a characteristic looping motion, arching its back as it walks like an inchworm; thin white lines along each side
• •What you see: Ragged holes in leaves of brassicas, lettuce, spinach, celery, and tomatoes; similar damage to imported cabbageworm but with a broader host range
• •Hosts: Cabbage family, lettuce, spinach, celery, parsley, tomatoes, cucumbers — broader than imported cabbageworm
• •Regions: Throughout the US; 3–5 generations per year in warm climates; overwinters in warm southern states and migrates northward. Year-round pest in Zone 8+.

• •Organic controls: (1) Bt kurstaki — highly effective; apply to all leaf surfaces including undersides; repeat after rain. (2) Spinosad. (3) Row cover to prevent egg-laying. (4) Hand-pick larvae.
• •Natural enemies to protect: Trichogramma parasitic wasps (attack eggs); Microplitis brassicae (larval parasitoid); spiders; ground beetles; birds
• •Cultural controls: Row cover is the most effective prevention. Check plants 2–3 times per week. Loopers are often present alongside imported cabbageworm, so the same management serves both.

Section 5: Beetles & Weevils

Beetles (order Coleoptera) are the most species-rich order of insects on earth. Most beetle species are beneficial or neutral in the garden; a small number are significant pests. Both larvae and adults of pest beetle species may cause damage, sometimes in very different ways. Beetles are generally harder to control with organic tools than soft-bodied insects or caterpillars, making cultural and physical controls especially important.

Colorado Potato Beetle (Leptinotarsa decemlineata)

• •Adult: 3/8″ oval beetle; yellow-orange with 10 black stripes on wing covers; hard-shelled; found on plant surfaces
• •Larva: Plump, red-orange with black spots; rows of black spots along the sides; humpbacked; feeds in groups; 1/2″ – 3/4″ when mature
• •Eggs: Bright yellow-orange oval eggs in clusters of 20–40 on leaf undersides
• •What you see: Heavily skeletonized leaves; complete defoliation in severe infestations; egg clusters on leaf undersides; all life stages may be present simultaneously
• •Hosts: Potatoes, tomatoes, eggplant, peppers — primarily Solanaceae family
• •Regions: Throughout the US east of the Rockies; lower pressure in the Rocky Mountain states and Pacific Coast. Has developed resistance to many synthetic insecticides in many regions.

• •Organic controls: (1) Hand-pick adults, larvae, and crush egg masses daily when populations are low. (2) Bt tenebrionis — the specific Bt strain for beetle larvae; must be consumed by larvae; less effective on large larvae. (3) Spinosad. (4) Kaolin clay applied to the whole plant surface — deters adults from feeding and egg-laying. (5) Pyrethrin. (6) Neem oil deters egg-laying.
• •Natural enemies to protect: Edovum puttleri parasitic wasp (attacks eggs); Perillus bioculatus (spined soldier bug); ground beetles consume eggs and young larvae
• •Cultural controls: Crop rotation — adults overwinter in soil, so rotating Solanaceae to new beds each year forces adults to walk farther to find hosts. Straw mulch provides habitat for ground beetles that eat eggs and larvae. Inspect plants daily during adult emergence. Use eggplant as a trap crop to draw beetles away from potatoes.

Cucumber Beetles (Acalymma vittatum — striped; Diabrotica undecimpunctata — spotted)

• •Striped cucumber beetle: 1/4″; yellow with 3 black stripes; often seen on flowers; vectors bacterial wilt disease (Erwinia tracheiphila)
• •Spotted cucumber beetle: 1/4″; greenish-yellow with 12 black spots; same pest group, broader host range
• •What you see: Adult feeding on flowers, pollen, leaves, and fruit rinds; plant wilt from bacterial wilt transmission; larval root damage underground; use the thread test for bacterial wilt (see Section 1)
• •Hosts: Cucumbers (most susceptible to bacterial wilt), squash, melons, pumpkins; spotted beetle also damages corn and beans
• •Regions: Striped: eastern and central US. Spotted: throughout the US. Both emerge in spring when plants are first transplanted — the most vulnerable period.

• •Organic controls: (1) Row cover from transplanting through early bloom — critical for preventing bacterial wilt transmission during the vulnerable seedling period; remove for pollination. (2) Hand-pick adults in early morning when sluggish. (3) Kaolin clay on all plant surfaces. (4) Pyrethrin. (5) Spinosad. (6) Yellow sticky traps for monitoring.
• •Natural enemies to protect: Tachinid flies (larval parasitoids); parasitic nematodes on larvae; ground beetles
• •Cultural controls: Plant resistant cucumber varieties ('Saladin,' 'Marketmore 76,' 'Diva'). Use transplants rather than direct seeding — larger plants are less vulnerable. Grow companion plants that deter beetles: catnip, tansy, radish. Remove and destroy any plant confirmed to have bacterial wilt immediately.

Japanese Beetle (Popillia japonica)

• •Adult: 1/2″; distinctive metallic green thorax and copper-brown wing covers; tuft of white hairs along each side of the abdomen; adults feed in groups; peak summer emergence
• •Larva: C-shaped white grub — see white grub profile in Section 3 for larval management
• •What you see: Adults skeletonize leaves (consume all tissue between veins, leaving a lace-like skeleton); heavily damaged flowers and fruit; adults often congregate in large numbers, preferring the sun-exposed top of plants
• •Hosts (adults): Roses, grapes, raspberries, beans, corn silk, apple, linden, Japanese maple, and 300+ other plant species
• •Regions: Eastern US (east of the Mississippi primarily, expanding into the Midwest and some western states). Peak adult emergence late June through August. Adults live 4–6 weeks.

• •Organic controls: (1) Hand-pick into soapy water in early morning — adults are sluggish and drop when disturbed; hold the bucket under the branch and tap it. (2) Kaolin clay on plant surfaces — deters feeding and reduces egg-laying. (3) Pyrethrin for severe infestations. (4) Row cover during peak adult flight protects vulnerable plants. DO NOT use Japanese beetle traps — research consistently shows they attract more beetles than they capture, increasing damage in the surrounding area.
• •Natural enemies to protect: Tiphia vernalis parasitic wasp (attacks grubs); Istocheta aldrichi fly (attacks adults); birds
• •Cultural controls: See Section 3 (white grubs) for larval management. Grow resistant plants where possible: forsythia, arborvitae, boxwood, junipers, and many native plants are less preferred.

Flea Beetles (Epitrix spp. on Solanaceae; Phyllotreta spp. on Brassicas; many other species)

• •Size: 1/16″ – 1/8″; tiny hard-shelled beetles with enlarged hind femurs for jumping; hop when disturbed
• •Color: Shiny black (most common); blue-black; or striped — varies by species
• •What you see: Numerous tiny round holes across leaves giving a "shotgun" or "shot-hole" appearance; seedlings most vulnerable; worst in spring and early summer
• •Hosts: Brassica seedlings — turnips, arugula, radish, cabbage family (Phyllotreta spp.); eggplant, tomato, potato, pepper (Epitrix spp.); also affect corn, beans, spinach
• •Regions: All regions; spring emergence is the most critical period when seedlings are most vulnerable. Populations typically peak in early spring and again in late summer.

• •Organic controls: (1) Row cover from seeding or transplanting through establishment — most effective prevention for spring seedlings. (2) Diatomaceous earth applied to soil surface and plant base. (3) Kaolin clay on plant surfaces. (4) Yellow sticky traps at plant height for monitoring and some population reduction. (5) Pyrethrin for severe infestations. (6) Spinosad.
• •Natural enemies to protect: Ground beetles and rove beetles consume flea beetle larvae and pupae in the soil
• •Cultural controls: Seed or transplant early in cool weather when flea beetles are less active. Start with larger transplants (4–6 inches) that tolerate early feeding better than seedlings. Use trap crops: radish draws flea beetles away from other brassicas; mustard attracts Phyllotreta beetles.

Section 6: Other Common Pests — Slugs, Earwigs, Leafhoppers, Leafminers & More

This section covers common garden pests that don't fit neatly into the beetle, caterpillar, or sucking insect categories but are frequently encountered and sometimes difficult to identify or control.

Slugs & Snails (Arion spp., Deroceras spp. — slugs; Cornu aspersum and others — snails)

• •What they are: Mollusks, not insects; slugs lack shells; snails have coiled shells; both are soft-bodied and nocturnal; leave characteristic slime trails
• •Size: Slugs 1/2″ – 3″; snails 3/4″ – 1.5″ with shell
• •What you see: Irregular holes in leaves with smooth edges; complete consumption of seedlings; slime trails on leaves, soil, and nearby surfaces; primarily nocturnal — rarely seen in daylight; worst in cool, moist conditions
• •Hosts: Almost any plant; particularly damaging to seedlings, lettuce, hostas, strawberries, and the cabbage family; thrives under mulch
• •Regions: All regions; most severe in the Pacific Northwest, Northeast, and other high-humidity climates. Population explosions after cool, wet springs.

• •Organic controls: (1) Iron phosphate bait (Sluggo, Escar-Go) — highly effective; safe for wildlife, pets, and children; OMRI-listed; apply in the evening when slugs are active; reapply after rain. (2) Diatomaceous earth around plant bases (loses effectiveness when wet; must be reapplied). (3) Copper tape as a barrier around raised beds — electrical charge deters slug crossing. (4) Hand-pick at night with a flashlight; drop into soapy water or salt. (5) Beer traps (containers sunk to rim level, filled with beer — slugs drown; effective but requires frequent emptying).
• •Natural enemies to protect: Ground beetles; rove beetles; toads and frogs (excellent slug predators — a toad in the garden is worth a dozen treatments); garter snakes; birds (especially robins and ducks)
• •Cultural controls: Reduce moisture and mulch depth in slug-prone areas during wet seasons. Water in the morning rather than evening so the soil surface dries before nightfall. Eliminate hiding spots (boards, dense ground covers, leaf piles) near vulnerable plants.

Earwigs (Forficula auricularia — European earwig)

• •Appearance: 3/4″ – 1″; reddish-brown; distinctive rear pincers (forceps); 6 legs; wings folded under short wing covers; nocturnal; moves quickly
• •Role in garden: IMPORTANT — earwigs are omnivores. They eat plant material AND pest insects (aphids, insect eggs, soft-bodied larvae). They are considered beneficial in many situations; management is warranted only when plant damage is significant.
• •What you see: Ragged holes in flowers, soft leaves, and seedlings; damage to corn silk and strawberry fruit; no slime trail (distinguishes from slug damage); found hiding in mulch, under boards, and in curled leaves during the day
• •Hosts: Marigolds, dahlias, lettuces, strawberries, corn, soft-tissue seedlings; significant plant damage is most common only in dense populations
• •Regions: Throughout the US; most populations in the western states are European earwig, introduced in the early 20th century. They are abundant and largely beneficial.

• •Organic controls (only when damage warrants): (1) Eliminate hiding places — reduce mulch depth near vulnerable plants; remove boards and debris. (2) Trap: roll up damp newspaper at night and dispose of in the morning; or use a tuna can filled with a small amount of oil — earwigs fall in and drown. (3) Diatomaceous earth around plant bases. (4) Spinosad for severe situations.
• •Natural enemies to protect: Tachinid flies (Bigonicheta spinipennis — a specific earwig parasitoid); toads; ground beetles
• •Cultural controls: Assess whether earwigs are actually causing significant damage before treating — they consume significant numbers of aphids and other pests and are often a net benefit. Damage from earwigs is often confused with slug damage; look for slime trails to distinguish.

Leafhoppers (Empoasca fabae — potato leafhopper; Macrosteles quadrilineatus — aster leafhopper; many species)

• •Appearance: 1/8″ – 1/4″; wedge-shaped; green, yellow, or brown; hold wings tent-like over body; fly and hop sideways rapidly when disturbed
• •What you see: Stippled, pale leaves; "hopperburn" (potato leafhopper) — leaf edges turn yellow then brown and curl under; stunted growth; some species vector plant diseases (aster yellows — Macrosteles spp.; beet curly top — Circulifer tenellus)
• •Hosts: Potatoes, beans, grapes, apples, alfalfa (potato leafhopper); aster family and many ornamentals (aster leafhopper); sugar beets, tomatoes (beet leafhopper)
• •Regions: Potato leafhopper: eastern US; migrates north from the Gulf Coast each spring; particularly severe in the Midwest and Northeast on potatoes and beans. Aster leafhopper: throughout the US.

• •Organic controls: (1) Insecticidal soap applied to leaf undersides where nymphs feed. (2) Pyrethrin. (3) Neem oil as a deterrent. (4) Row cover prevents infestation on beans and potatoes.
• •Natural enemies to protect: Anagrus epos parasitic wasp (attacks leafhopper eggs in grape vineyards); spiders; minute pirate bugs; assassin bugs
• •Cultural controls: Reflective silver mulch significantly reduces leafhopper landing. Monitor with yellow sticky traps. Remove weeds that serve as leafhopper reservoirs. For aster yellows disease: remove infected plants immediately (there is no cure) and control the leafhopper vector in susceptible plantings.

Leafminers (Liriomyza sativae, Agromyza spp., Phyllocnistis citrella, and many other species)

• •What they are: Larvae of small flies, moths, or beetles that mine (tunnel) between the upper and lower leaf surfaces, leaving characteristic visible trails or blotches
• •What you see: Serpentine (winding) pale yellow-white trails or irregular blotches (depending on species) visible on the leaf surface; leaf tissue intact but pale where mined; hold the leaf to light to see the larva in early stages
• •Hosts: Spinach, beet, chard (Pegomya spp.); beans, tomatoes, peppers (Liriomyza spp.); citrus (Phyllocnistis); columbine and many ornamentals — host specificity varies by species
• •Regions: Different species throughout the US. Liriomyza vegetable leafminer is most prevalent in California, Florida, and the South. Columbine leafminer affects ornamentals throughout the eastern US.

• •Organic controls: (1) Spinosad — most effective; must be applied when adults are flying, as eggs and larvae inside the leaf are protected from contact sprays. (2) Neem oil as a deterrent to adult egg-laying. (3) Remove and destroy mined leaves — the larvae are inside; removing them removes the pest. (4) Yellow sticky traps to capture adult flies and reduce egg-laying.
• •Natural enemies to protect: Diglyphus isaea parasitic wasp — a highly effective natural enemy of leafminer larvae; present naturally in gardens; can be purchased commercially for greenhouse use
• •Cultural controls: Row cover prevents adult egg-laying. If a mine is still active (larva visible inside), squish the end of the mine to kill the larva before removing the leaf. Avoid broad-spectrum spraying that kills D. isaea.

Section 7: Vertebrate Pests — Deer, Rabbits, Voles, Gophers & Birds

Vertebrate pests — mammals and birds — are among the most frustrating garden challenges because they are mobile, intelligent, persistent, and often legally protected. Management relies primarily on exclusion (physical barriers), deterrents, and habitat modification rather than lethal control, which is regulated by state and federal wildlife laws. Always verify local regulations before attempting to trap or relocate any vertebrate pest.

Section 8: Beneficial Insects — Your Most Important Allies

An estimated 97 percent of insect species are either beneficial to gardens or are neutral. Only 3 percent of insects are garden pests. The gardener who understands this invests in supporting beneficial insect populations rather than spraying broadly against the minority that cause damage. A garden rich in beneficial insects has dramatically fewer pest problems than one managed primarily with pesticides — including organic pesticides — that disrupt the natural enemy community.

How to Attract and Support Beneficial Insects

• •Plant for nectar and pollen: Adult beneficial insects (including parasitic wasps, hoverflies, lacewings, and predatory bugs) feed on nectar and pollen as adults. A diverse planting of small-flowered plants in the carrot family (Daucus, Coriandrum, Anethum, Ammi), composite family (Achillea, Echinacea, Coreopsis, Cosmos), and mint family (Salvia, Nepeta, Monarda) provides the resources these insects need to establish and reproduce in your garden.
• •Avoid broad-spectrum pesticides: Every application of pyrethrin, neem oil, or insecticidal soap that contacts beneficial insects reduces their populations. Use organic pesticides only when necessary, in targeted spot applications, in the evening after bee activity, and only on the specific plant that has a pest problem. The beneficial insect community recovers more slowly than pest populations after disruption.
• •Provide habitat: Beneficial insects need shelter, overwintering sites, and water. Leaving some stems standing through winter (hollow stems house native bees); keeping a brush pile or rock pile at the garden's edge; providing a shallow water source; and tolerating some 'weedy' areas that flower early provide habitat that a purely manicured garden cannot.
• •Tolerate low pest populations: Some pest presence is necessary to maintain a population of natural enemies. A garden with zero pests has nothing for the beneficial insects to eat; they leave. A garden with a low, controlled pest population maintains the natural enemy community that provides free, ongoing pest suppression. The goal is not zero pests; it is pests below the level of significant damage.

Key Beneficial Insects: Identification & Value

Section 9: Crop-by-Crop Pest Reference

This section provides a quick reference for the most important pests affecting each major vegetable and fruit crop, with first-response organic control recommendations. For detailed control information, refer to the pest profile sections earlier in this guide.

Section 10: Seasonal Pest Calendar & IPM Decision Framework

Pest management is most efficient when it is anticipatory rather than reactive. The following seasonal calendar helps you prepare for predictable pest pressure before it peaks, and the IPM (Integrated Pest Management) framework provides a decision structure for choosing the most appropriate response to any pest situation.

The IPM Decision Framework: What to Do When You Find a Pest

Integrated Pest Management (IPM) is the decision framework used by professional growers, cooperative extension services, and the most effective home gardeners. It prioritizes the least disruptive effective control at every step, escalating to more intensive interventions only when necessary.

• •Identify the pest correctly: Do not treat until you know what you are treating. Misidentification leads to using the wrong product, harming beneficial insects, and wasting money. Use the symptom key in Section 1, the pest profiles in Sections 2–7, and your state extension service resources.
• •Assess the damage level: Is the damage significant? A few aphids on a healthy plant are being managed by natural enemies and do not require intervention. A colony of aphids covering all new growth on a stressed plant requires action. The threshold question: is the pest present at a level that will cause meaningful damage if left unmanaged?
• •Consider the context: Is the plant at a vulnerable stage (seedling, transplant shock, fruit set) or a more resilient stage (established, mature)? Are beneficial insects present? Is this an isolated problem or widespread? What is the weather trend — will conditions favor or disfavor the pest?
• •Apply cultural and physical controls first: Can you remove the pest by hand? Apply a water spray? Apply row cover? Improve conditions to reduce pest favorability? These actions have no risk to beneficial insects and no pesticide resistance potential.
• •Apply targeted organic pesticides if necessary: Choose the most specific, least disruptive product effective against the identified pest. Bt is highly specific to its target and has no effect on beneficial insects; use it before broad-spectrum products like pyrethrin. Apply in the evening; target only affected plants or plant sections.
• •Evaluate and adjust: Did the treatment work? If not, why not? Was the identification correct? Was the product applied at the right time and in the right way? Adjust the approach based on observed results.