Holes in Basil Leaves: How to Identify and Stop Common Garden Pests

Basil is a crop that's all leaves. Its large, lush foliage is grown for its fragrance and, most importantly, for its taste. That's why it's especially upsetting if you go to harvest your basil and find it full of holes. Not only does it make it less appealing (who wants a garnish someone else has munched on first?), it can be a sign of a larger infestation that could seriously hurt your plant in the long run.

In this article we'll cover how to identify the most common basil pests, as well as how to get rid of them and keep them from coming back. Let's dive into this important part of basil care.

What's Eating My Basil?

Before you can do anything about holes in your basil leaves, you need to know who the culprit is. Basil has a strong herbal scent and flavor that deters a lot of pests, especially birds and mammals. It's the bugs and other invertebrates you've got to watch out for.

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The most common nibblers are snails and slugs, Japanese beetles, earwigs, aphids and other soft-bodied insects. Now that you know who is desecrating your basil, you need to know how to stop them.

Slugs and Snails

Mollusks move slowly but are quick to make short work out of your basil leaves. Normally a good thing, mulch provides hiding places for these pests during the day. You could remove the mulch, but the slugs probably come back anyway. A better option is to cover the mulch with diatomaceous earth.

Diatomaceous earth is very sharp and pierces the skin of soft-bodied slugs and snails, which dehydrates and eventually kills them. Water and rain allows the diatomaceous earth to soak into the soil, so you should reapply it regularly. Crushed eggshells or wood ashes will have a similar effect.

Garden detritus also gives these pests a place to hide and lay eggs, so be sure to keep your basil beds weeded and clear.

Slugs and snails can also be hand picked at night. If that's too hands-on for you, you can always make a slug trap or buy one on Amazon. Look for some of the newer safer slug baits that contain iron phosphate. There are also baits that contain metaldehyde (Buggeta) and carbaryl (Sevin) for non-organic growers.

Japanese Beetles

If your basil’s leaves have become skeletonized, the culprit is likely Japanese beetles. These little menaces target over 300 other species of plant, and will eat flowers and buds as well. They're present for about one month in high summer.

Adults are a metallic green/bronze beetle with white hair-like tufting beneath the wings and larvae are cream-white grubs found in the soil. Japanese beetles produce a generation every 1-2 years. The larvae overwinter in the soil.

Pheromone traps should not be used as they tend to attract more beetles rather than deter them. Floating row covers over kaolin clay can help deter adults. Adults can also be handpicked and dispatched in soapy water.

Beneficial nematodes introduced into the soil will help to reduce the numbers of overwintering grubs. Both neem oil and insecticidal soaps can reduce the number of adult beetles.

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Earwigs

Earwigs look scary, and to your basil plant they are. Experts at hiding, they feed on basil and other plants at night. They love dark, moist areas of the garden where they will hide until nightfall.

Because earwigs like hidey holes, a deterrent is to place basil grown in containers atop bricks or “feet”made for pots to raise the container and eliminate any hiding places.

It’s possible to get a handle on but not completely eradicate earwigs by using chemical controls. Carbaryl garden dust can reduce their numbers. Sprinkle the dust along the edges of the basil container or around the base of the plant. The downside is that this product is easily washed away when irrigating or during rainfall.

Aphids and Soft Bodied Insects

Aphids can be almost any color and may be found atop or on the underside of leaves and even on stems. Heavy infestations result in yellow/distorted necrosis on leaves along with honeydew – the sticky, sugary substance aphids secrete. Honeydew adds to the problem by promoting sooty mold.

An insecticidal soap can help to control aphids and other soft bodied pests. Spray with a spray bottle in the early evening and pay attention to covering the underside of the leaves as well as above.

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How to Keep Bugs from Eating Basil

There are several ways to deter pests from eating basil. Cover the plant with row covers when Japanese beetles are imminent, use diatomaceous earth around the plant to deter soft bodied pests like snails and slugs, and spray with an insecticidal soap or neem ensuring entire coverage of the plant at the first sign of pest attack.

Keep the plant healthy, fed and consistently watered. Keep the area near and around the basil free from weeds and other detritus where pests might hide. Take a good look at your basil on a daily basis for any pest damage or pests that can be handpicked.

Note: Any recommendations pertaining to the use of chemicals are for informational purposes only. Chemical control should only be used as a last resort, as organic approaches are safer and more environmentally friendly.