What Is Eating the Leaves of My Basil Plants?

Basil (Ocimum basilicum) originally hails from Asia, but you can now find it growing in backyards throughout U.S. Department of Agriculture plant hardiness zones 2 through 11. You're not the only one who enjoys the taste of basil -- if you notice something has been chewing away at your basil plant's leaves, identify the pest and take immediate measures to protect your crop from hungry insects.

The Japanese beetle is one of the most common pests to target basil, warns Clemson Cooperative Extension. The beetles show up in the early summer and eat most of the basil leaf but don't touch the veins of the leaf, resulting in a lace-like texture in the foliage. Handpick the beetles off of the plants and crush them. Or put a bucket of soapy water under the basil bush and shake it; this dislodges the beetles and they drown in the soapy water below.

For future prevention of infestations, the pungent odor of garlic (Allium sativum) deters and repels Japanese beetles. Planting garlic among basil can protect the basil from the pests. Garlic thrives in full-sun locations in USDA plant hardiness zones 3 through 8.

Spreading mulch around the basil plants helps conserve soil moisture and improves basil health, but it can also be a hiding spot for another common basil pest: slugs. If you notice slime trails around the basil and missing leaves or stems on the lower portions of the plant, you have a slug problem. Instead of removing the mulch, sprinkle a circle of diatomaceous earth around the base of each basil plant. This powder has tiny, sharp edges that cut slugs as they crawl over the power, dehydrating and killing them. Replenish the powder after it rains. Avoid inhaling the powder or getting it in your eyes or mouth.

Additionally, try slug traps. This pest is drawn to the smell of fermentation. Place a tray filled with beer among the basil plants. The smell of the beer entices the slugs, but the liquid proves to be their downfall and drowns them. Traps remain effective for a long time, attracting and killing slugs until the beer evaporates completely.

If you notice little brown, green, yellow, black or red dots moving across the foliage of the basil plant, aphids are the culprit. Though aphids can be found throughout most gardens, they cause plant damage when their populations get too high. The pests feed on the juices in the basil plant's leaves, causing wilting, yellowing and stunted growth. You'll typically find aphid activity at its peak when temperatures range between 65 and 80 degrees Fahrenheit.

Ants encourage aphid activity. Putting a sticky ring around the base of each basil plant to prevent ants from crawling up the plant helps control aphid populations. Weeds are also a source of aphids that then infest the garden, so keeping weeds at bay deters the pests. If cultural controls don't work, spray an insecticidal soap. Mix 2 to 4 teaspoons of dish soap in a quart of water, and spray it on the basil plant wherever aphids are present. The soapy solution kills the pests on contact.

True to their name, whiteflies are small, dusty white flies that swarm around the basil plant and tend to congregate on the underside of the basil foliage. They feed on the juices of the basil leaves and can cause widespread foliage drop. Like most basil pests, whiteflies are most active in the summer.

Shoot down affected basil shrubs with a strong blast of water from a garden hose. This is often dislodges and kills enough whiteflies that pest populations stay below harmful levels. Alternatively, use a handheld vacuum. Head out to the basil plants in the early morning when whiteflies are sluggish, and suck up the flies with the vacuum. After a few mornings of doing this, populations should be low enough to be relatively harmless. If all else fails, mixing a homemade insecticidal soap just as you would for aphids will eradicate the pests. Repeat once a week until whiteflies are controlled.