Prevent Thrips on Plants Naturally with These 10 Must-Know Tips

Thrips on plants in your garden or indoors can cause a lot of damage. Here’s how to stop these pests with simple organic techniques.

Thrips on plants can spell trouble for gardens, houseplant collections, and greenhouses. But thrips are often overlooked because they are so small and the damage they cause looks similar to that of spider mites and aphids. This guide will help you identify thrips and the damage they cause so you can prevent and get rid of infestations before they spread.

What Are Thrips?

Also known as thunder flies, thrips are tiny, sap-sucking insects in the Thysanoptera order. There are thousands of thrip species, and many types benefit gardens by pollinating plants or preying on pests. However, some thrips, including rose thrips, onion thrips, and western flower thrips, damage plants. They can weaken vegetables and flowers and even spread plant diseases.

What Do Thrips Look Like?

Mostly active during the summer months, thrips come in assorted shades of brown, black, and white, and often congregate on the undersides of infested plants. Although there are some wingless thrips, most thrips have small, fringed wings and slender, tapering bodies that rarely measure over 1/16 of an inch long. While thrips are not strong fliers, they easily move about on the wind, and they overwinter in the soil, which can create ongoing issues for gardeners if infestations aren’t addressed.

Identifying Thrip Damage on Plants

Many types of thrips are specialist feeders that only target specific types of plants. However, some thrips are generalists that are equally attracted to vegetables, ornamentals, herbs, and houseplants. These pests commonly affect food crops like asparagus, tomatoes, and beans, but they also plague most houseplants and ornamentals, such as carnations, chrysanthemums, gladiolus, and pansies.

Tips

If you suspect thrips are damaging your plants, place a sheet of white paper beneath the affected plant leaves and give the plant a good shake. This should dislodge any thrips (and any other small pests) onto the paper and make them easy to spot.

Thrip damage is often confused with aphid issues and plant nutrient deficiencies. Looking for these signs and symptoms can help you identify thrip problems before they get out of hand:

• Yellow or brown stippling or streaking on plant leaves
• Plant leaves with a silvery sheen or a bleached look
• Misshapen fruit, flowers, and leaves
• Stunted plant growth
• Black speckles of frass on leaves
• Plants covered in a sticky “honeydew” residue. Dark, sooty mold occasionally develops on top of the sticky honeydew.
• Plant diseases, like wilt. These diseases can be transmitted by thrips when they feed.

Preventing Thrip Infestations

Preventing thrips from invading your garden and houseplants is much easier than addressing active thrip infestations, and it’s the best way to reduce pesticide use and limit the spread of diseases like wilt. Deterring thrips is relatively easy, and many of these thrip prevention tips will help you repel other common plant pests, including aphids and spider mites.

1. Inspect New Plants

The number one way to prevent indoor thrips is to inspect and quarantine new plants before you bring them into your home or greenhouse. Thrips can also hitch a ride indoors on houseplants that are kept outside during summer, as well as cut flowers and fresh produce, so you might want to inspect these items too and spray them with an organic soap spray as a preventative.

2. Maintain Healthy Plants

Healthy plants repel pests much better than sick and stressed plants, so make sure to provide plants with the proper amounts of light, water, and fertilizer. Take care not to use too much fertilizer, though, as overfertilizing can cause plants to produce new, tender growth, which attracts thrips.

Related: The 10 Best Fertilizers for Indoor Plants of 2024 to Help Your Greenery Thrive

3. Stay on Top of Weeds

Thrips use certain weeds as host plants for their eggs. Keep weedy areas of your yard cut back to deprive them of a place to call home.

4. Clean Up Your Garden

Keep plant diseases and pests from spreading by cleaning up and destroying infested plant material. It’s usually best to burn infested plant debris or bag it and throw it in the trash because thrips can survive the composting process.

5. Try Companion Planting

Basil and other strongly scented herbs naturally repel thrips, while flowering plants, like yarrow, dill, and parsley, attract ladybugs and other thrip predators. Growing these plant companions near crops that thrips feed on can keep your garden naturally pest-free.

6. Install Row Covers

If you have an ongoing issue with thrips, install finely woven row covers over vulnerable crops at the beginning of the season. This should keep thrips from laying eggs on your plants, and you can remove the covers later to admit pollinators.

7. Prune at the Right Time

Newly pruned plants are vulnerable to thrip damage, but you can avoid thrip issues by pruning plants when thrips aren’t active. Although different plants need to be pruned at different times of the year, winter pruning is usually the best option for avoiding thrips.

Related: A Guide to Pruning Plants for Healthier Trees, Shrubs, and Flowers

8. Choose Resistant Plants

Growing plants that are naturally less appealing to thrips can make your garden easier to keep. For instance, western flower thrips are known to love pale roses with strong fragrances, but they aren’t as interested in scent-free, dark roses that produce tight flower buds.

9. Use Reflective Mulches

Reflective mulches applied around your garden help conceal plants from thrips and other pests. For a budget-friendly alternative, place sheets of aluminum foil beneath your plants to “foil” thrips.

10. Add Sticky Traps

Blue sticky traps placed strategically around houseplants and greenhouses can help you identify thrip problems early on. Keep in mind that these traps work best as a preventative, not a treatment, and they can harm pollinators if you use them outdoors.

How to Get Rid of Thrips

Despite our best efforts, thrips can still sometimes occur on indoor and outdoor plants. When problems arise, don’t stress or reach for synthetic pesticides. Many pesticide products affect pollinators, and they can also make pest problems worse by harming the beneficial bugs that prey on thrips.

Instead of using pesticides:

• Treat affected plants by washing them in a sink or with a garden hose. As you work, rinse the tops and bottoms of infested leaves and along the plant stems where the leaves attach.
• Scrape away the top layer of soil around potted plants and prune away and destroy heavily infested leaves.
• Release predatory insects like lacewings or ladybugs on outdoor or greenhouse plants.
• Spray the plants with organic soap or neem oil. Just remember that sprays can harm pollinators and other beneficial insects, so don’t apply them to the flowers or in conjunction with predatory insects. Sprays should only be used in the evening to avoid issues with sunscald, and they may need to be reapplied several times at 7- to 10-day intervals to treat adult thrips and any nymphs that hatch after the initial treatment.

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