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CoastLine: Crape Murder, Gardening Mischief, and Ideas for Summer Planting

Photo: Rachel Lewis Hilburn; gardenia: Jeff Hunter
Thrips on a gardenia cutting. The insects won't harm the plant, but they will turn the petals brown prematurely.

If we had an in-studio camera on this episode, you would have seen two people wearing headphones, a series of microphone set-ups, and sitting on top of a small, round table covered with a layer of green felt, you would notice a mason jar filled with a cutting from a Gardenia bush.  If you looked more closely at the jar, you would have observed tiny insects covering the petals of the white Gardenia blossom.  On this edition of CoastLine, we find out from plant and garden expert Tom Ericson what these bugs are and what to do about them. 

We also learn why Tom is on a crusade to put a stop to the Cape Fear region’s annual Crepe Murder rampage, the yearly massacre of Crepe Myrtle trees, chopping them back to a few unsightly sticks in the hopes they’ll blossom more fully in the spring.  And we get pointers on plants that will thrive in hot summers on the southeastern coast.


Tom Ericson, The Transplanted Garden  

Thrips: Flower thrips (Frankliniella tritici), Western flower thrips (F. occidentalis) and various other thrips species are pests of gardenia flowers. Thrips are slender, dark-colored insects, with fringed wings. Adults are less than 1/16 inch in length. To see these fast-moving pests, you need a magnifying lens. Thrips are typically found on leaves and between flower petals. Both adults and nymphs (immature insect stages that resemble the adult, but are smaller) feed by scraping surface cells to suck plant sap.

When thrips feed on flower buds, the flower may die without opening. With a light infestation, their feeding causes leaves to have silvery speckles or streaks. With severe infestations, flowers are stunted and distorted and may turn brown and die.

Thrips feed also on expanding leaves, which creates purplish red spots on the undersurfaces and causes foliage to severely curl or roll, then drop prematurely.

As a result of their small size, thrips are difficult to detect before damage is obvious. To sample for thrips on gardenia flowers, hold a sheet of stiff white paper under injured flowers, and then tap the flower. Examine the paper in bright sunlight. Any thrips present will move around on the paper. In addition, blowing lightly into the blooms causes thrips to move around, making them easier to see.

Control: Several naturally-occurring enemies feed on thrips. To avoid killing these beneficial insects which reduce thrips populations, insecticides should be avoided as much as possible. Grass and weeds in the area should be kept mowed or removed when possible.  Predators would be Lady Beetles (the correct term for ladybugs) and Lacewings.

If it becomes essential to spray an insecticide, the following are available in homeowner-size packaging: bifenthrin, cyfluthrin, lambda cyhalothrin, permethrin, or spinosad. Acephate (Orthene) is a foliar, systemic spray insecticide that will better control thrips that are within flower buds than contact insecticides. Spray when thrips are present and again in 7 to 10 days. Soil drenches or granular applications of dinotefuran, disulfoton or imidacloprid  (avoid this one at all cost.  It is HIGHLY toxic to Honeybees) will give some thrips suppression.