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Hibiscus Plant Care

Thrips

My Buds are Falling off Before they Bloom!

What if you've done everything right and your hibiscus are growing well with lots of green foliage, but the buds on your plants are falling off the plants before they open into gorgeous flowers? Well, you probably are experiencing the scourge of flowering plants - the lowly thrip.


Healthy Hibiscus Buds
Identifying Thrips: Thrips are insects that lay their eggs inside the buds of hibiscus, roses, and other species that make big buds before flowering. The thrip is small but visible if you look for it. The easiest way to see thrips is to take an open flower and shake it over a white piece of paper. Thrips will fall out of the flower onto the paper, looking like small, black pencil lines on the paper. They are much longer than they are wide, and their dark color stands out against a piece of white paper.


Off-Color Bud
Infested with Thrips
Bud Drop: The typical sign of thrips is a bud that grows large, turns an off-color before opening, and then falls from the plant at the slightest pressure. Buds may sometimes fall before turning color, but often that sort of rotten color happens before the buds fall. The reason for this change in the big, healthy bud is that the thrips have been scratching around inside the bud as well as laying eggs inside of it. When the bud falls, the young thrips are then able to leave the bud and burrow into the ground where they change into adult thrips that are capable of flying back up to new buds to continue the cycle.

Thrips Scratches on Hibiscus Flower
Thrips Scratch Marks on a 'Bon Temps' Hibiscus Flower
Scratch Marks: Some varieties of hibiscus do not react to thrips by losing their buds. In that case you can see the thrips damage as scratch marks on the flower petals. Sometimes it looks almost natural, like the spots and markings that some of our varieties produce as part of their interesting flower coloring. Other times you can see how it badly mars the beauty of the flowers. Even though these varieties do not lose their buds they can still be treated in order to obtain flawless blooms free of thrips scratches.

Treatment: Fortunately, there is a simple and effective treatment for thrips. For fast and full results, it is best to remove all rotten buds from the plants and the ground and dispose of them in the trash. In order to keep thrips under control, you will need to use a product called Spinosad. This chemical needs to be sprayed over the tops of the plants, covering the buds and upper leaves of the plants. Use Spinosad for three treatments, 5-7 days apart. Each treatment will dramatically reduce the number of thrips and increase the number of flowers that open normally. Three treatments is usually enough to end the infestation, but you may repeat this treatment series if you need to. You can also drench the potting mix or soil around a hibiscus with a systemic pest control product. This will kill most of the live thrips that are living in the ground in the juvenile form, and it will speed up control of this pest.

Thrips Scratches on Hibiscus Flower
Thrips Scratch Marks on a 'Voodoo Magic' Hibiscus Flower
Organic Treatment: If you don't want to use pesticides, an organic approach is to spray in the same way with any product containing "Neem oil," a natural product obtained from the Neem tree. It may require more treatments to control thrips, but is a good alternative approach if combined with gathering up all rotten buds and spent flowers so the thrips do not reach the ground around the plant.

A Note to Hibiscus Growers in Florida and the Deep South: A new insect arrived in the USA a few years ago that can also cause bud drop. Called the "hibiscus gall midge," this tiny fly causes hibiscus buds to turn bright yellow when they are still very small and then fall off the plant. They differ from thrips, which cause large, almost-ready-to-open buds to turn an off-color brownish and fall from the plants. Control of this midge is much the same as for thrips, but it requires a more aggressive treatment program that includes both spraying and soaking the soil around the plants with acephate or imidacloprid (active ingredient) products. If your plants have hibiscus gall midge, contact your local county agriculture department for more info on treatment of hibiscus gall midge in your area.


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