Garden pest guide
Identify and control the 8 most common garden pests
— pest by crop, with the science.
Most of the pest damage in home gardens and on houseplants traces back to just eight species groups. Here is what each one looks like, which crops it hits hardest, and the integrated-pest-management protocol that actually clears it — organic where possible, with biological controls flagged at every step.
The 8 pests covered
Click any pest for full identification photos, the crops it affects, and the integrated control protocol.
Pest by crop — the affected-host matrix
Every pest x crop combination documented in authoritative extension sources. Click a cell to open the dedicated pairing page with symptoms, timing, and protocol.
| Pest \ Crop | Tomatoes | Peppers | Basil | Lettuce | Cucumbers | Roses | Beans | Seedlings | Strawberries | Citrus |
|---|---|---|---|---|---|---|---|---|---|---|
| Aphids | X | X | — | X | X | X | X | — | — | X |
| Spider mites | X | — | — | — | X | X | X | — | X | — |
| Whitefly | X | X | — | — | X | — | — | — | X | — |
| Fungus gnats | X | — | X | X | — | — | — | X | — | — |
| Thrips | X | X | — | — | X | X | — | — | — | — |
| Mealybugs | X | — | X | — | — | — | — | — | X | X |
| Scale insects | — | — | — | — | — | X | — | — | — | X |
| Slugs | — | — | — | X | — | — | X | X | X | — |
X = documented host in our reviewed sources. Em-dash = not a primary host (do not assume safe; verify against your local extension service for unusual hosts).
One-line pest summaries
For the gardener who just wants to know what they are looking at.
- AphidsAphidoidea (superfamily)
Aphids are 1-4 mm pear-shaped sap-suckers that cluster on new growth and leaf undersides. They reproduce asexually, so a few become thousands within weeks. Knock colonies off with a strong water blast, follow with insecticidal soap or neem every 5 days for three weeks, and release ladybugs or lacewings for severe cases.
- Spider mitesTetranychidae (Tetranychus urticae most common)
Spider mites are microscopic 0.5 mm arachnids that thrive in hot, dry, dusty conditions. They stipple leaves with tiny yellow flecks and spin fine webbing once populations build. Raise humidity, hose foliage hard, and apply insecticidal soap or horticultural oil weekly. Release Phytoseiulus persimilis predatory mites for severe greenhouse outbreaks.
- WhiteflyAleyrodidae (Trialeurodes vaporariorum, Bemisia tabaci)
Whiteflies are 1-2 mm white moth-like insects that fly up in a cloud when foliage is disturbed. They suck sap, excrete honeydew, and vector several plant viruses. Yellow sticky traps catch adults, silver reflective mulch confuses incoming flights, and insecticidal soap or neem every 5 days knocks back nymphs. Encarsia formosa is the standard greenhouse parasitoid.
- Fungus gnatsSciaridae (Bradysia spp.)
Fungus gnats are 2-3 mm dark flies that swarm around damp potting mix. Adults are harmless; larvae chew tender roots and seedling stems. Let the top inch of soil dry between waterings, top-dress with sand or BTI granules (Bacillus thuringiensis israelensis), and trap adults with yellow sticky cards. Drench severe pots with a Bti solution every 7-14 days.
- ThripsThysanoptera (Frankliniella occidentalis, Thrips tabaci)
Thrips are slender 1-2 mm insects that rasp leaf surfaces and suck the released sap, leaving silvery scars and black faecal specks. Western flower thrips also vector tomato spotted wilt virus. Blue sticky traps catch adults, weekly insecticidal soap or spinosad targets larvae, and Orius insidiosus (minute pirate bug) or Amblyseius swirskii are the standard biocontrols.
- MealybugsPseudococcidae (Planococcus citri most common)
Mealybugs are 3-6 mm pink soft-bodied scale insects covered in white cottony wax. They cluster in leaf joints, on stems, and on roots. Dab adults with rubbing alcohol on a cotton swab, then apply horticultural oil or insecticidal soap every 7 days for a month. Cryptolaemus montrouzieri larvae are effective for severe greenhouse infestations.
- Scale insectsCoccoidea (armored: Diaspididae; soft: Coccidae)
Scale insects are immobile 1-5 mm bumps stuck to stems and leaves — armoured scales have a hard shield, soft scales produce honeydew. Time horticultural oil sprays for the crawler stage (newly hatched, wax-free nymphs) when they are vulnerable. On houseplants, scrape adults off and follow with weekly oil sprays for a month.
- SlugsGastropoda (multiple families incl. Arionidae, Limacidae)
Slugs leave silvery slime trails and ragged, lacy holes in soft leaves and ripening fruit. They feed at night and in damp conditions, especially during spring and autumn. Iron-phosphate pellets (organic-approved) and beer traps both work; copper barriers help, and hand-picking after dark is brutally effective on small plots.
How to use this pest guide
Start with the matrix above. Find the crop you are growing along the top row, then look down the pest column to see what is documented on that crop. Click any X to open the dedicated combo page with symptoms, timing windows, and the integrated-pest-management protocol — biological control first, organic spray second, and conventional sprays only as a labelled last resort.
If you do not know which pest you are looking at, snap a photo in Growli; we cross-check the image against species hosts and tell you what protocol to follow for your specific crop, growing condition, and zone.
What this guide does not cover
Larger garden pests (cabbage white caterpillars, vine weevil, carrot fly, codling moth) and rodent or vertebrate pests are out of scope for this matrix — they need crop-specific protocols rather than the cross-cutting IPM approach used here. The same goes for soil-borne disease (root rot, fusarium wilt) and foliar disease (mildew, blight), which are covered in our houseplant diseases guide.
Where the science comes from
Every claim in this guide is sourced from one or more of: US Cooperative Extension services (UC IPM, NC State, UMD, UMN, Penn State, CSU), UF/IFAS EDIS publications, Clemson HGIC fact sheets, the Royal Horticultural Society, and Cornell NYS IPM Biocontrol fact sheets. Where the science is genuinely ambiguous (e.g. less-documented host crops for a pest), we drop the combo rather than fabricate. The dataset is curated by the Growli editorial team and reviewed quarterly.
Pesticide safety
Any chemical-control recommendation in this guide is generic — products and approvals change every season. Always read the product label and follow manufacturer's PPE, dosage, and re-entry guidance. Pesticide approvals change — confirm via the UK HSE pesticide register or US EPA before use. Neonicotinoids (imidacloprid, clothianidin, thiamethoxam) are not recommended in any of our protocols; their UK approvals have lapsed (HSE rejected emergency authorisation in January 2025) and pollinator risk is well documented.
Frequently asked questions
- What are the most common garden pests?
- Across home gardens and houseplants, eight pests cover most of the cases gardeners run into: aphids, spider mites, whitefly, fungus gnats, thrips, mealybugs, scale insects, and slugs. Aphids are usually the most widespread; spider mites and whitefly dominate hot, dry, or sheltered conditions; fungus gnats are the houseplant and seedling problem; thrips matter mainly because they vector tomato spotted wilt virus.
- How do I identify a pest on my plants?
- Look at three things: size and location (where exactly on the plant), what they leave behind (webbing means spider mites, white wax means mealybugs, slime trails mean slugs, honeydew points to aphids, whitefly, or scale), and how they move (whitefly fly, aphids walk slowly, scale does not move at all). Open Growli, snap a photo, and the app will confirm the species and recommend the right protocol.
- What is the safest pest control for edible plants?
- Insecticidal soap and horticultural oil are the two safest broad-use sprays — both work by physical contact, leave no residue once dry, and are approved for use on edibles right up to harvest. Bacillus thuringiensis israelensis (Bti) is the standard for fungus gnat larvae in seedling trays. Iron-phosphate pellets are the safest slug bait. Biological controls (ladybirds, lacewings, parasitoid wasps, predatory mites) are the best long-term answer.
- Do neonicotinoids still work for garden pests?
- Neonicotinoids (imidacloprid, clothianidin, thiamethoxam) have been progressively restricted because of pollinator harm. The UK HSE rejected emergency authorisation in January 2025, and EU approvals lapsed. Most extension services no longer recommend them for home or commercial use on flowering crops. Use insecticidal soap, neem, spinosad (at dusk to protect bees), or biocontrols instead.
- How fast do garden pests reproduce?
- Faster than most gardeners expect. Aphids can complete a generation in 7-10 days and reproduce asexually. Spider mites complete egg-to-adult in 7 days at 27 degC. Whitefly takes 3-4 weeks under glass. Mealybug females lay 300-600 eggs in a single cottony sac. This is why single-treatment sprays nearly always fail — you have to maintain a 2-3 week protocol that catches each new hatch.
- Can I prevent pests rather than treat them?
- Yes, and prevention is cheaper than control. Inspect new plants before bringing them home; quarantine new arrivals for 3 weeks; avoid high-nitrogen feeding that drives soft, pest-attractive growth; water consistently to avoid drought stress (which amplifies mite damage); use silver reflective mulch under outdoor vegetables; and plant a few alyssum or fennel as predator bankers to keep ladybirds and lacewings on site.
- When during the season do pests appear?
- Aphids appear from the first spring growth flush. Slugs peak in spring and autumn during wet mild weather. Spider mites and whitefly explode in midsummer heat. Thrips arrive with transplants and weedy field edges. Fungus gnats are year-round indoors. Scale crawlers emerge in two waves (May and August) on outdoor woody plants. Mark these windows on your calendar and inspect weekly.
- Should I use chemical pesticides on my vegetable garden?
- Most home vegetable gardens never need synthetic pesticides. Insecticidal soap, horticultural oil, neem oil, spinosad, and Bti cover almost every situation safely. If chemical use is unavoidable, choose products with short pre-harvest intervals, apply at dusk to protect pollinators, and rotate active ingredients so populations cannot adapt. Always read the product label and confirm the active ingredient is currently approved via the UK HSE register or US EPA.
Keep going
- Garden pest identification — the complete article
- How to get rid of aphids on plants
- Spider mites on houseplants treatment
- Fungus gnats — full kill guide
- Mealybugs on plants
- Scale insects — identification and control
- Companion planting chart (pest-deterrent pairings)
Diagnose a pest in Growli
Snap a photo of the bug, the leaf, or the slime trail. Growli identifies the pest, cross-references it against your plant species and growing conditions, and gives you a step-by-step organic protocol for clearing it.
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