Frequently distinguished by a set of pincers on the tip of their abdomens, earwigs are nocturnal insects that feed on a wide range of plants and small animals. In total, there are about 2,000 species of these six-legged creatures. All of them are classified under the suborder Neodermaptera, which has a global distribution. While these insects may be beneficial in some contexts, their infestations have often been associated with heavy and irreversible crop damage.
Earwigs are named for their hindwings, the shape of which has been likened to human ears. Not all earwigs unfold and use these wings to fly, however. Many of them retain a wholly flightless lifestyle, often burrowing into the soil, searching for food by crawling along plant stems, and taking shelter in leaf litter. The common and troublesome European earwig (Forficula auricularia) is known for creeping into homes and subsisting on food in the cupboards!
While these insects may be perceived as pests, they can also be desirable as beneficial insects due to their predatory nature (for some species). Their true benefits are brought out when they are found in naturally regulated abundances. Thus, some horticulturists opt to grow plants that either attract these predators or repel them with a mixture of aromatic compounds.
1) Common wormwood (Artemisia absinthium)
Often cultivated as a novelty herb and as a pest-repellent plant, common wormwood is a textural perennial with wondrous properties. Its erect stems, which grow to about 3 feet (91 cm) tall in optimal conditions, produce greenish-grey and multi-lobed leaves. These are densely covered in trichomes and oil glands that produce a notably bitter cocktail of terpenoids.
Terpenoids are organic phytochemicals with secondary functions in plants. In the common wormwood, these compounds likely function as a natural pest deterrent and aid in protecting the leaves from larger grazers. They have shown potential as additives in botanical insecticides, which can effectively protect crops without damaging their appearance or negatively impacting the environment. Earwigs are just one group of insects that this species’ terpenoids seem to repel.
Wormwood cuttings can be distributed around the home or garden, particularly in areas where pests are most likely to congregate. Mature plants can be situated next to more vulnerable ornamentals or crops. Some of this species’ best companion plants, which also happen to have their own pest-repellent properties, include rosemary, leeks, onion, and sage.
2) Dill (Anethum graveolens)
Dill is widely grown as a culinary herb due to its fragrant and intensely flavorful leaves. It is an annual plant that favors mild to warm conditions, requiring the heat and light levels of summer to produce a substantial amount of foliage. After it produces seeds, its shoots may begin to die back. The seeds can then be collected, dried, and re-planted in an organically rich and well-draining substrate during the next warm period.
Fairly straightforward to cultivate and grow, dill is a great addition to just about any type of garden. Its thread-like leaves and umbels of white to yellow blooms attract dozens of pollinators and beneficial insects. One of these is the tachinid fly, a parasitoid that helps control earwig populations in a stealthy manner. This fly’s larvae can internally parasitize earwigs and many other life stages of pests, including beetle pupae and moth larvae. The unsuspecting earwigs consume the tachinid fly’s eggs, which eventually hatch and feed on their host’s internal tissues.
To ensure that your stands of dill remain healthy enough to attract a diversity of beneficial insects, make sure they are planted in a brightly lit and well-ventilated spot in the garden. Note that, while dill does make a fine companion plant for some vegetables, its mature specimens may compromise the growth of others. You may opt to restrict its roots to within their own dedicated containers or pots.
3) Basil (Ocimum basilicum)
This tender plant is one of the most economically important herbs due to its value as a culinary ingredient. Now available in various cultivars, each with its own unique phytochemistry, basil is grown in many mild to warm climates outside of its native range. This means that its natural benefits, which include insect control, garden diversification, and bacterial inhibition, can benefit home gardens in Europe and the Americas.
Basil’s essential oil, which is largely composed of linalool and estragole, has been deemed to be effective as an insect repellent. Tested against thrips, beetles, mosquitoes, and nematodes, its oil has toxic properties that, when used by humans, can also serve a medicinal purpose. The strong scent emitted by the oil, which is released whenever the plant is mechanically damaged, repels earwigs.
Periodically harvesting the fully grown leaves of your basil plants should release their scent and ward off many insects. If you would like to continuously use basil as an insect repellent, it would be best to harvest its leaves and create an organic insecticidal solution. This can be sprayed onto the foliage of other vulnerable plants. Pure extracts of its oil can likewise be used and should be a fine option for indoor application.
4) Bay tree (Laurus nobilis)
The bay tree, bay laurel, or sweet bay is a lovely addition to medium-sized gardens in regions with a mild year-round climate. Evergreen, it can be grown as a shrub or provided with ample space and support to become a small tree. Symbolic of immortality and prosperity, it may very well be the plant that your garden needs to reduce the chances of pest infestations.
The fresh or dried leaves of the bay tree can ward off grain beetles, flies, moths, earwigs, and even cockroaches. You may generously distribute them around vulnerable plants or grains. To increase their effectiveness, you may also tie them up into small bundles, place them in fireproof containers, and burn them. The smoke produced by burning leaves, which should resemble that of incense, should have pests scrambling to find an escape route.
If you’ve seen earwigs inside your cabinets and cupboards, a plate of freshly collected bay leaves might drive them out. A well-kept bay tree should sustain all of your culinary and pest-related needs for its leaves, so make sure your plant is situated under full sun and rooted into well-draining soil. Mint, lavender, and citrus-scented herbs can be grown close to the crown of the tree.
5) Fennel (Foeniculum vulgare)
A member of Apiaceae (the carrot family), fennel is widely cultivated for the flavorful and bulb-like base of its shoot and for its strongly-scented seeds. Its unique flavor profile is attributed to a compound called anethole, which is found in its essential oil. The oil also contains other volatile phytochemicals, such as estragole and fenchone. These have pest-repellent properties due to their strong scent.
Although fennel produces a complex cocktail of insecticidal compounds, it isn’t all that effective on its own as an earwig-repellent plant. Instead, it is similar to dill in that it attracts one of the earwig’s major threats in the wild – the tachinid fly. Drawn to the inflorescences of fennel, this fly lays its eggs on the surface of the leaves or directly on the backs of unsuspecting insects. The eggs hatch into larvae which make their way into the host insect.
Once an earwig has been victimized by parasitoid larvae, there’s hardly any hope for its survival. The larva exits the insect as a maggot that subsisted on the earwig’s fat stores. The host is usually killed before its internal organs have become completely damaged. The relationship between fennel and these silent, hidden killers is precisely what makes it so threatening to troublesome insects.
6) Garlic (Allium sativum)
The pungent smell emitted by crushed garlic is extremely unappealing to many garden pests, earwigs included. Attributed to the presence of sulfur-containing compounds in its essential oil, its strong aroma is often related to a seemingly “hot” or spicy sensation. The compounded effects of each of its potent phytochemicals can be directly targeted to earwigs via a garlic-and-pepper spray.
To make your own garlic-based spray, it would be best to use freshly harvested bulbs from your garden or local market. Finely mashed, the garlic cloves may be combined with cayenne pepper and mixed into slightly soapy water. This spray can be applied to the leaves of vulnerable plants. Once earwigs and other pests gain wind of the strong scent, they are likely to travel in the opposite direction and search for food elsewhere.
In the garden, intact bulbs and their leaves may dissuade earwigs from coming too close to your vegetable patch. They are exponentially more effective, however, if they emit their strong scent. Nonetheless, it won’t hurt to plant patches of garlic around vulnerable crops and ornamental flowers. It is highly beneficial as a companion plant for fruit trees and valuable tubers.
7) Pot marigold (Calendula officinalis)
Calendula can be quite tricky to use as an insect-repellent plant because it attracts its own host of pests (e.g. aphids, thrips, whiteflies, and slugs). These pests may, in turn, appeal to predatory insects, some of which are beneficial and some of which are troublesome. If kept in good shape, beneficial insects should be drawn to pot marigolds by their blooms and natural features instead of by the pests they could harbor.
In the home garden, pot marigolds can be grown to attract tachinid flies. These parasitoids, which also favor dill and fennel, should help control earwig populations that occur on the pot marigold itself or on the shoots of nearby plants. Any earwigs that attempt to eat pot marigold leaves are likely to consume the parasitoid’s eggs.
There are cases, however, when it would actually be beneficial to have a small population of earwigs (particularly the predatory types) on your pot marigold. Earwigs are voracious feeders of aphids and other soft-bodied insects, which tend to infest pot marigolds that are weakened or situated in sub-optimal conditions.
8) Peppermint (Mentha x piperita)
As peppermint is a mint hybrid, it is naturally found in areas where both of its parent plants (water mint and spearmint) occur. Its strong and appealing fragrance is one of its most valuable features; though its oil appeals to humans, it repels many herbivores and plant-eating insects. This low-maintenance hybrid is truly one of the best herbs to cultivate in a pest-repellent garden.
Characterized by deep-green, fuzzy, and serrated leaves, peppermint is a rapid grower that vegetatively spreads via underground runners. It favors moist substrates and partially shaded locations. It is thus perfect for repelling earwigs that may be tempted to damage plants along the borders of outdoor water features. To release its pest-repellent fragrance, aim to periodically prune the shoots or harvest the leaves.
Harvested leaves and cuttings can be distributed around the garden or placed in indoor locations where earwigs might be found. Just make sure to dispose of these before they rot and attract bacteria or fungi. The leaves can also be ground up and added to an organic pest-repellent spray.
9) Sweet alyssum (Lobularia maritima)
A member of the Brassicaceae family of crucifers, sweet alyssum is a low-growing and trailing annual. Best used as a groundcover, filler, or cascading plant, its densely branched shoots can grow as tall as 12 inches (30 cm). Its blooms, which are present all throughout the year in regions with mild climates, are white, pink, lilac, or yellow. As these occur in eye-catching inflorescences on mature plants, they attract a wealth of pollinators and beneficial insects.
The mode by which sweet alyssum prevents earwig infestations is by attracting the tachinid fly and other beneficial insects. To increase its chances of successfully drawing in these parasitoids, plant it alongside stands of dill and fennel. The increased surface area on which the flies can land and lay their eggs should help protect surrounding plants from earwigs.
If your fruit trees, roses, leafy greens, and root crops are often plagued by earwigs, consider cultivating sweet alyssum as a companion plant. Avoid growing it close to water-loving species, however, as its roots can easily rot in waterlogged substrates.
10) Coriander (Coriandrum sativum)
Also known as cilantro and Chinese parsley, coriander is a valuable annual herb with many uses in the home garden and kitchen. Its lobed and feathery foliage is remarkably flavorful due to its potent phytochemicals. Linalool, which is known for having insect-repellent properties, is the major component of its essential oil. Though coriander seeds have a different flavor compared to the leaves, they also owe their taste to linalool.
Like dill, fennel, and sweet alyssum, this useful herb attracts tachinid flies to the garden. Moreover, when its leaves are mechanically damaged, the scent emitted by the leaked sap should discourage earwigs from coming too close. In the absence of inflorescences that attract beneficial parasitoids, this plant can at least defend itself using its oils.
Unlike sweet alyssum, coriander would make a great companion plant for water-loving herbs. It can also be planted alongside valuable fruit and vegetable-producing crops such as eggplant, various beans, and peppers. Make sure to allow its stands to develop their inflorescences so that they can attract a whole host of beneficial insects (e.g. ladybugs, syrphid flies, lacewings).
Very good Info! Thank You 😊
Very useful and interesting info. Will try to use some of the suggestions next spring.