Herbs are not pest-free just because they are strongly scented. Basil attracts aphids and whiteflies, mint attracts flea beetles and spider mites, rosemary can be troubled by spider mites in hot, dry weather, and slugs will eat young parsley and cilantro overnight. The good news is that herbs are rarely destroyed by pests — the damage is usually cosmetic, and the controls are simple, because herbs are eaten fresh and often, so the gentlest control is usually the right one.
The rule for herbs is organic-first and spray-last. You are going to eat these leaves, often raw, so anything you spray on them matters. Start by identifying the pest, check whether the damage is actually serious, and use hand-picking, water, barriers and predators before you reach for any spray. This guide covers the pests that matter for herbs, how to recognise them, and what to do. Use our pest identifier helper if you are unsure what you are looking at, and check your local extension service for advice on which pests are active in your area.
Aphids on herbs
Aphids are the most common herb pest. They are small, pear-shaped insects that cluster on soft new growth and the undersides of leaves, sucking the sap. Basil is a favourite, especially when it has been fed heavily and grown soft, and dill, parsley and mint are all attacked. The signs are curling, distorted young leaves, sticky honeydew on the leaves, and sooty mould growing on the honeydew. Aphids also spread viruses, though that is less of a problem on herbs that are picked and eaten quickly than on long-lived crops.
Control starts with a jet of water: blast the colonies off with a strong spray from a hose or a spray bottle, and repeat every few days until they are gone. Pinch off badly infested shoot tips and dispose of them. Encourage predators — ladybirds, lacewings and hoverflies all eat aphids, and a garden with flowers nearby will have more of them. Avoid heavy nitrogen feeding, which produces the soft growth aphids love. If you must spray, use a soap-based spray made for edible plants, follow the label, and observe the harvest interval — do not pick and eat sprayed leaves until the label says it is safe. Our guide to aphids control covers the full range of options.
Spider mites and whiteflies
Spider mites are tiny — almost invisible — and they thrive in hot, dry, still air, which is why they are a particular problem for indoor herbs and for rosemary, thyme and sage in a hot summer. The signs are fine yellow stippling on the leaves, a dull, dusty look, and fine webbing on the undersides of the leaves. Hold a white sheet of paper under a leaf and tap it: if tiny dark specks fall and move, you have spider mites. They spread fast in dry air, so raise the humidity by misting the leaves in the morning, water the plants well, and improve airflow. Wash the leaves with water to knock the mites off, and remove badly affected leaves. Our guide to spider mites on plants covers them in detail.
Whiteflies are small white insects that fly up in a cloud when the plant is disturbed. They attack basil, mint and sage, sucking sap and leaving honeydew. Hang yellow sticky traps near the plants to catch the adults and to monitor numbers, wash the leaves to remove eggs and nymphs from the undersides, and ventilate greenhouses and cold frames during the day. Our guide to whiteflies control explains the options. For both pests, the best prevention is a healthy plant in the right conditions — a stressed, dry, over-fed herb is far more attractive to mites and whiteflies than a healthy one.
Slugs, snails and caterpillars
Slugs and snails are the main enemy of young, soft herbs. They eat parsley, cilantro, basil and mint at night, leaving ragged holes and slime trails, and they can strip a young plant overnight in damp weather. Go out after dark with a torch and pick them off by hand — it is the most effective control there is. Protect young plants with copper tape around pots, with a ring of grit or crushed eggshells around the plant, and by keeping the area clear of damp hiding places such as boards and dense ground cover. Water in the morning, not the evening, so the soil surface dries before night. Our guide to slugs and snails control covers the full range, and our guide to eggshells in the garden explains how to use them as a barrier.
Caterpillars are less common on herbs than on vegetables, because most herb leaves taste too strong for them, but parsley and dill are host plants for the swallowtail butterfly, whose caterpillars eat the leaves. Many gardeners tolerate a few, because the butterflies are welcome, but if the caterpillars are stripping the plant, pick them off by hand and move them to a spare plant. Flea beetles make small round holes in mint and basil leaves — the damage is usually cosmetic on an established plant, and a fine mesh cover over young plants keeps the beetles off.
Indoor herb pests
Indoor herbs have their own pest problems, because the warm, dry, still air suits spider mites and fungus gnats in particular. Fungus gnats are small black flies that hover around damp compost; their larvae live in the top of the compost and can damage seedlings and young roots. Let the compost dry out between waterings — the surface should feel dry before you water again — and remove any dead leaves from the surface. Yellow sticky traps catch the adults, and a thin layer of grit on the compost surface makes it harder for them to lay eggs. Mealybugs are another indoor pest: white, cottony clusters in leaf joints, especially on rosemary kept indoors over winter. Dab them off with a cotton bud dipped in rubbing alcohol, or wash the plant with soapy water.
Quarantine any new plant before you put it with your other herbs — keep it apart for a week and check it for pests, because a single infested plant from a garden centre can infest a whole windowsill. And check indoor herbs weekly, turning the leaves over to look at the undersides, because pests build up fast in warm rooms and are much easier to deal with when there are only a few of them. If a pest problem indoors does not clear up, check your local extension service for advice on products labelled for indoor use.
Prevention: healthy herbs resist pests
The best pest control is a healthy herb in the right conditions. Give each herb the sun, soil and water it wants, and it will be far less attractive to pests than a stressed plant. Do not over-feed: soft, sappy growth from heavy nitrogen feeding is the first thing aphids attack. Give plants space and airflow, so the leaves dry quickly and pests cannot hide in a dense, damp clump — our plant spacing calculator can help you work out spacing. Water at the base in the morning, not over the leaves in the evening. Remove dead leaves and spent plants promptly, because they shelter slugs and harbour disease.
Plant flowers nearby to attract predators and pollinators: marigolds, calendula, alyssum and nasturtiums all bring ladybirds, lacewings and hoverflies into the garden, and those predators eat aphids and other pests for free. Grow a diversity of herbs rather than a single block of one kind — a mixed herb bed confuses pests and supports more predators than a monoculture. And accept a little damage: a few holes in a mint leaf do not matter, and a herb garden with no insects at all is a garden with no predators either. Act when the damage is spreading or the plant is suffering, not at the first hole.
Spraying herbs safely
If you do need to spray, choose the gentlest option that works, and always read the label. Soap-based sprays and horticultural oils are the usual first choice for herbs, and they work by smothering soft-bodied insects such as aphids and whiteflies. They only work on contact, so spray the undersides of the leaves as well as the tops, and repeat after a few days to catch the insects that hatch afterwards. Do not spray in hot sun, because the spray can scorch the leaves, and do not spray when bees are active — spray in the evening, when pollinators have gone home.
Observe the harvest interval on the label: it tells you how many days to wait after spraying before you pick and eat the leaves, and it matters. Wash all herbs before eating, whether or not they have been sprayed. Avoid broad-spectrum insecticides on herbs entirely — they kill predators as well as pests, they leave residues on leaves you are going to eat, and they often make the pest problem worse in the long run by killing the predators that were keeping it in check. If a pest problem is beyond soap sprays and hand-picking, check your local extension service for the products that are approved for edible herbs in your area.
Common mistakes
The most common mistake is spraying first and diagnosing later — a broad-spectrum spray on a herb you are about to eat, for a pest you have not identified, is the worst of both worlds. The second is over-feeding, which produces the soft growth aphids love. The third is ignoring indoor pests until they have spread to every pot on the windowsill — check weekly, and quarantine new plants. The fourth is watering in the evening, which gives slugs a damp night to feed in. And the fifth is expecting a pest-free garden: a few holes and a few aphids are normal, and the predators that eat them are part of a healthy herb garden. Deal with the pests that are actually damaging the plant, and leave the rest alone.
| Pest | Herbs most affected | Signs | First control |
|---|---|---|---|
| Aphids | Basil, dill, parsley, mint | Clusters on soft growth; curling leaves; honeydew | Jet of water; pinch off tips; encourage ladybirds |
| Spider mites | Rosemary, thyme, sage; indoor herbs | Fine stippling; webbing under leaves | Raise humidity; wash leaves; improve airflow |
| Whiteflies | Basil, mint, sage | Cloud of white insects when disturbed | Yellow sticky traps; wash leaf undersides |
| Slugs and snails | Parsley, cilantro, basil, mint | Ragged holes; slime trails; night feeding | Hand-pick after dark; copper tape; grit barrier |
| Fungus gnats | Indoor herbs in damp compost | Small black flies around pots | Let compost dry; grit on surface; sticky traps |
| Flea beetles | Mint, basil | Small round holes in leaves | Fine mesh over young plants |
Frequently asked questions
What is eating my basil leaves?
Look at the damage: aphids cluster on soft new growth and curl the leaves, slugs leave ragged holes and slime trails, whiteflies fly up in a cloud when disturbed, and flea beetles make small round holes. Identify the pest first, then use the gentlest control — water jets and hand-picking before any spray.
How do I get rid of aphids on herbs?
Blast them off with a strong jet of water and repeat every few days, pinch off badly infested shoot tips, encourage ladybirds and lacewings, and avoid heavy nitrogen feeding. If you must spray, use a soap-based spray made for edible plants and observe the harvest interval on the label.
Are spider mites common on rosemary?
Yes, especially in hot, dry, still air — indoors in winter and in a hot summer outdoors. Look for fine yellow stippling and webbing on the undersides of leaves. Raise humidity, wash the leaves with water, improve airflow, and water the plant well.
How do I stop slugs eating my herbs?
Pick them off by hand after dark, use copper tape around pots and a ring of grit or crushed eggshells around plants, keep the area clear of damp hiding places, and water in the morning so the soil surface dries before night.
Can I spray herbs I am going to eat?
You can use soap-based sprays and horticultural oils made for edible plants, but always read the label, spray in the evening when bees are not active, observe the harvest interval before picking, and wash the herbs before eating. Avoid broad-spectrum insecticides on herbs.