What's Bugging You? Thrips
Thrips - (Frankliniella occidentalis)
If you have had a rose or orchid that has come into bud and suddenly the bud does not open or falls off the plant, one very likely cause may be thrips.
Thrips are very tiny insects that are so small you will need a microscope to see one properly. They often appear in colonies, attacking flower buds, leaf buds and new growth. The 5000 plus species are predominately found on outdoor plants but there are a few species that affect houseplants and flowering houseplants. Thrips can be light brown, tan, yellow or black, with narrow cylindrical bodies. They may or may not have fringe (long hairs) on the edge of their translucent wings. They can crawl or fly from plant to plant. Thrips feed on plants much like aphids; puncturing the plant cells and devouring their cellular contents.
While they are not considered dangerous to humans, their bite can cause itching at the bite site and a pinkish dotted rash. They do not transmit disease to humans.
Thrips can enter your home in many ways. They can fly into your home on their own; on a plant that you have recently purchased or on your clothes. They often come in on tropical plants that have summered outdoors and are brought in for the winter. Even a slight breeze will carry them from yard to yard.
Thrips complete their life cycle in five stages; egg, larval, pre-pupal, pupal and adult. Adult females can live up to 30 days and lay 2-10 eggs per day. Prepupal and pupal stages can be found on a plant or in the soil.
Some species of thrips will lay their white or yellow eggs by creating a wound in the soft tissue of a plant and inserting the egg in the wound. This can be inside a leaf, stem, flower-bud, fruit or in groups on the underside of leaves.
About half of thrips species lay their eggs on the underside of leaves without puncturing the plant. They produce a special glue that will hold the eggs on the leaf even in high winds.
Many thrips species are able to reproduce without males to fertilize the eggs. Unfertilized eggs will produce only females which are clones of the mother. These ‘clones’ will become reproducing females as well. In other species, females and males mate and the female stores enough sperm from that mating to fertilize eggs for its entire life. Their offspring will be male and female. The males have a shorter lifespan than the females.
The signs and symptoms of thrips are many.
They can be found in flowers and flower buds. They also love to eat flower pollen. Thrips often appear on the undersides of young leaves and in leaf buds. Their presence distorts young leaves and fruit. Black specks of shiny excrement will be on the leaves along with yellow speckled feeding areas. Flower petals are often spotted. Thrips will attack older leaves as well and the leaf will show silver colored speckles. A lot of the signs may remain long after they have left but it does tell you they are in the vicinity.
You have discovered one of your plants has thrips. What do you do?
First, isolate the affected plant and check any surrounding plants for thrip damage as well.
Wash off the plant with a forceful spray of water. Do not do this step with plants that have hairy leaves such as African violets.
Prune off any buds, flowers or leaves that show excessive damage. Place all clippings into an outside garbage can.
You can also wipe down the front and back of leaves with a soft cloth and water.
Place yellow and blue sticky strips near or in the affected plants and in the other plants in your home.
The next step would be to spra y the plant with a natural insecticide such as EndAll insecticidal soap by Safers. It is safe to use indoors, around humans and pets. Again, do not spray plants that have hairy leaves. It is safe to use the insecticidal soap every 10 days for a month or two.
Lastly inspect every plant you bring into your house. Isolate any new plants for a few days and check for insects again.
FYI – Thrips prefer mild, cool temperatures. Warm, hot temperatures shorten their lifespan.
Thrips hibernate in winter. They can hibernate at any stage of their development and will come out of hibernation in spring.