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How to Treat Thrips on Gardenias

By Barbara Fahs ; Updated September 21, 2017

Gardenia flowers have a scent that many people describe as heavenly. These large white blooms are favorites for corsages. But this plant can be subject to insects, such as thrips, which affect its health and cause the flower buds to drop. Thrips are tiny insects, 1/16-inch long, and the adults can fly. Some people say thrips look like “worms with legs.” If you provide your gardenia with the growing conditions it favors—acidic soil that is rich, well drained and in partial shade—you’ll be a step ahead of the bugs by helping your plant to fight off this opportunistic invader.

Controlling Thrips on Gardenias

Watch for leaves that either shrink in size or curl up. Thrips also cause yellow spots on leaves. May is prime time for thrips, so keep this in mind when you monitor your gardenias for this pest.

Spray your gardenia with insecticidal soap as soon as you detect any thrips.

Introduce natural controls in the form of beneficial insects. Ladybugs, some predatory mites and predatory nematodes will eat the thrips. You can purchase many types of beneficial insects at nurseries and on the Internet.

Apply chemical pesticides if your thrips invasion becomes serious. Recommended chemicals include malathion, diazinon, chlorpyrifos and acephate.

Test your soil and correct the pH if necessary: To increase acidity, add sulfur to the soil. To lower acidity, add dolomitic limestone or hydrated lime.

 

Things You Will Need

  • Spray bottle
  • Insecticidal soap
  • Predatory insects
  • Chemical pesticide
  • Soil test kit

Tips

  • Gardenias prefer to have their leaves dry, so avoid misting them and growing them under trees that can drip water on them.
  • If you order beneficial insects on the Internet, be sure you check with local authorities to make certain they are allowed in your state. (For example, Hawaii restricts the introduction of insects such as these.)

Warning

  • Follow label instructions carefully if you choose to use chemical pesticides.

About the Author

 

Barbara Fahs lives on Hawaii island, where she has created Hi'iaka's Healing Herb Garden. Fahs wrote "Super Simple Guide to Creating Hawaiian Gardens" and has been a professional writer since 1984. She contributes to "Big Island Weekly," "Ke Ola" magazine and various websites. She earned her Bachelor of Arts at University of California, Santa Barbara and her Master of Arts from San Jose State University.