Thrips attack and discolor the buds of flowers (especially roses) causing them to open poorly or not at all. Thrips belong to the insect order Thysanoptera and are so tiny they often appear to be nothing more than little black specs moving over your flowers.
Most Thrips are minute (.5mm) but can grow up to 1/8″ long. There are over 600 different species in North America and many species in Utah. Some thrips have wings and are adept at flying, sometimes capable of flying for many hours. Others are entirely wingless and crawl or jump to move around. All have slender bodies, short antennae, and six short legs.
Not all thrips cause plant damage, some are actually helpful because they attach aphids, mites, and even other thrips. They have unusual asymmetrical mouthparts that combine piercing and rasping elements, enabling them to saw through plant tissues, and then suck out the juices. Females with saw-like ovipositors cut slits into flower stems to lay their eggs. There are usually several generations each year. In the course of feeding, it is possible they will transmit fungal and bacterial plant diseases in the same way mosquitoes transmit malaria.
You can use Imidacloprid (Hi Yield Systemic Granules) on non-edible plants. It takes about a week to enter a rose’s system, which is when it starts to poison the sucking thrips. Apply at the first sign of damage, and repeat every six weeks until mid August. For vegetables, try Bonide Hop Pepper Wax (a repellant) or Spinosad (a bacterial control). Apply to the flowers and stems three times at weekly intervals. Be sure to follow the “days to harvest” label.
Make sure and follow current label instructions of any pesticide used, as sometimes label directions change. And don’t forget, you can always stop by any Western Garden Center and talk to one of our expert gardeners.
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