Western flower thrips feed on much more than flowers. In fact, this group sucks the sap out of over 250 different plants. They can also bring tomato spotted wilt and other tospoviruses to your garden. And they bite!
Western flower thrips (Frankliniella occidentalis) are native to the Southwestern United States but have spread to several other continents on contaminated plant material. [Yes, Virginia, invasiveness goes in all directions.] In fact, western flower thrips have earned the dubious distinction of being one of the world’s most important agricultural pests. And they have developed a resistance to many insecticides, so don’t bother spraying. Some scientists believe that western flower thrips have become such a problem and experienced such a significant population explosion as a result of genetic mutations caused by the insecticides we used to try to kill them. Oops.
Western flower thrips description
Male thrips of any type are rare. The same is true for this species. If you do see one, you might notice that they are yellowish-white. They are also larger than many other thrips, measuring up to a whopping 0.06 inches (1.4 mm). When male western flower thrips come together, they fight by flicking the tip of their abdomens at each other. Wouldn’t that be a sight?
Western flower thrips lifecycle
Like other thrips, females do not need to be mated to produce offspring. Eggs are laid in unopened buds and under the epidermis layer of leaves, flowers, and fruit, causing discoloration and distortions. When those eggs hatch, hungry, mobile larvae start feeding. They use raspy mouthparts to shred and pierce to get at the sugary sap they crave. When not eating, they hide in tight little spaces where they are difficult to find. After they have eaten their fill, they enter a two-step, non-feeding pupal stage. In some cases, they drop to the ground to pupate. There can be up to 15 generations each year.
Western flower thrips host plants
It would probably be easier to list the garden plants not affected by western flower thrips, but you need to see just how damaging these micro pests can be. Members of the carrot, broccoli, citrus, legume, melon, mint, onion, sage, stone fruit, and tomato families are all susceptible to western flower thrips. So are apples, artichokes, beets, blueberries, figs, grapes, lettuce, pistachios, rye, strawberries, and wheat. See what I mean?
These pests also feed on several native plants and many popular ornamentals, including carnations, chrysanthemum, gladiolas, impatiens, orchids, petunias, roses, and sweet peas. As thrips feed, their saliva damages the surrounding plant tissue. And nymphs feed heavily on newly forming fruit and leaves, causing damage and spreading disease.
But they aren’t all bad. Western flower thrips also feed on certain mites that attack cotton crops. [I still don’t want them in my garden.]
Western flower thrips damage
You may have to look closely to see these pests, but the damage they cause is more visible. As they feed, they leave behind scarring and stippling of petals, leaves, and other plant parts. You may also see distorted growing tips, pimpling of flower petals, or leaf silvering. The damage varies based on where and when the damage occurred. In some cases, you won’t see it until much later. This later damage may include distorted or spotted fruit, which bruises more easily, Fruit splitting may also occur and Western flower thrips are the main vector of tomato spotted wilt.
Being attracted to bright colors, especially blue, white, and yellow, these pests will land on people wearing those colors and bite them. Thrips won’t drink your blood or make you sick, but you might be uncomfortable for a while. And you can use that information to help control these pests.
Blue sticky sheets are very effective at attracting and capturing western flower thrips. Sadly, beneficial hoverflies are also attracted to those blue sticky sheets. You can protect those garden helpers by surrounding the blue sticky sheet with a mesh that will allow the thrips through, but not the hoverflies. Reflective mulches actively discourage western flower thrips and insidious flower bugs are particularly fond of western flower thrips. For dinner.
You can grow a surprising amount of food in your own yard. Ask me how!
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