3 Companion Plants Tomato Gardeners Recommend to Protect Tomatoes From Whiteflies

Key Points

Whiteflies multiply quickly and weaken tomato plants by sucking sap, causing yellowing, stunted growth, and reduced harvests.

Early prevention is key, and companion planting is one way of prevention. Sprays and traps are better for infestation.

Companion planting with marigolds, nasturtiums, or zinnias helps deter or manage whiteflies naturally.

Summer is when tomato plants really hit their stride, producing lush foliage, bright yellow blooms, and the promise of a plentiful harvest. But warm, dry weather doesn’t just encourage healthy tomato growth, it also creates ideal conditions for common garden pests.

Whiteflies are among the most troublesome, and tomatoes are one of their favorite hosts. If you’ve noticed tiny, white, moth-like insects fluttering up from your plants when you brush against them, it’s a sign that whiteflies may have moved in. Left unchecked, these sap-sucking pests can quickly weaken tomato plants and reduce your harvest, so early intervention is essential.

Here’s everything you need to know about protecting your tomatoes from whiteflies this summer, including clever companion-planting tricks pro gardeners recommend for keeping these common pests at bay.

Meet the Expert

Glen Chandler, founder of Evergreen Seeds, has over 15 years of experience in landscaping, garden maintenance, and garden design.

Nicole Johnsey Burke is founder of the online gardening platform Gardenary and the author of Kitchen Garden Revival, The 5-Minute Gardener, and Leaves, Roots and Fruit.

Signs of Whitefly Infestation

Whiteflies are generally regarded as one of the most challenging pests to control since they multiply so quickly, Glen Chandler, founder of Evergreen Seeds, says. A few whiteflies in the garden can turn into a full-blown infestation if you’re not careful, which can be devastating to nitrogen-heavy vegetable crops like tomatoes, peppers, eggplants, and cucumbers.

These tiny, sap-sucking pests may be called whiteflies, but they more closely resemble tiny white moths, which can confuse many beginner gardeners. And when we say tiny, we mean tiny. To give some context, whiteflies are closest in size to fungus gnats, making them smaller even than common fruit flies. This makes them hard to see and even harder to control.

So, besides physically seeing the pests, what are some other ways to tell if you have a whitefly infestation?

Nicole Johnsey Burke, founder of Gardenary, notes a few common signs:

“They suck the sap out of the leaves, and once they’ve settled in, you’ll see yellowing, stunted growth, and less fruit,” she says. “Whiteflies also leave behind a sticky honeydew that creates a black sooty mold, which blocks sunlight from your leaves.”

Whiteflies are most common in the summer and early fall when temperatures are hot and humid. They cannot survive freezing winters, so they are known for being especially prevalent indoors in greenhouses or in climates that experience mild winters.

Companion Plants That Repel Whiteflies

Whiteflies can be tricky to manage once an infestation has become established, so gardening pros rely on prevention to stop them before they settle in. Their go-to? Companion planting.

Here are three companion plants whiteflies hate.

Marigolds

Credit: Westend61 / Getty Images

Burke says marigolds (Tagetes spp.) are her top companion plant pick for protecting her tomatoes from whiteflies.

“Some varieties release a compound called limonene that seems to confuse and repel whiteflies,” she says. “I tuck them right into the same bed as my tomatoes along the border or in between plants.”

Nasturtiums

Credit: Patricia GUERIN / Getty Images

Next up are nasturtiums (Tropaeolum spp). This common trap crop releases root compounds that whiteflies don’t like, and it also helps to lure other unwanted pests, such as aphids, away from your tomatoes.

As a bonus, Burke says they add interest and variety to any garden, serving as spiller plants that flow beautifully over the edge of a bed.

Zinnias

Credit: lissart / Getty Images

Lastly, Burke recommends planting zinnias (Zinnia elegans) close to your tomatoes if you’re concerned about whiteflies. Zinnias don’t technically repel whiteflies, but they attract whitefly predators, like beneficial wasps.

Plus, you’ll get to enjoy the gorgeous zinnia blooms throughout the summer. Healthy tomatoes plus bright zinnia blooms equals a win-win.

Other Ways to Protect Tomatoes From Whiteflies

If whiteflies have already established themselves in your tomato plants, companion planting can help, but it probably won’t eliminate the problem. In the case of severe infestations, Chandler and Burke offered a few strategies to manage the population. These include:

Spray the plant, particularly the underside of the leaves, to remove any eggs and nymphs.

Apply insecticidal soap every four to five days for two weeks.

Add yellow sticky traps to your garden to catch adults. (Whiteflies love the color yellow!)

Read the original article on The Spruce