I’ve noticed that thrips have invaded some of my house plants; namely a zebra plant, which I caught too late, and an amaryllis.
I suspect they’re thrips, at the least: somewhat long, tiny, black bugs, younger ones are translucent, and highly infested leaves had tiny black dots all over that somewhat looked like oil slicks.
I tried to re-pot all of my plants with new potting soil (Miracle Gro Brand, for indoor plants), taking care to discard the old soil immediately. I also thoroughly washed the roots with water upon re-potting, have consistently washed the leaves with a dish soap and water solution, and placed them out of contact from my other plants. These plants all sit by a west-facing window; they’ve done well here for many years.
My zebra plant is now a leafless stem, and my amaryllis is just the bulb.
A couple of questions for you:
1) Is there any hope left for the amaryllis and zebra plant? Is there anything that I can do to facilitate regrowth?
2) I have seven or eight arabica plants, a spider plant, and a succulent nearby. I’ve begun to notice a few thrips on the arabica plants, and killed/ removed them immediately. I really don’t want these plants to become infected.
Are there any more preventative measures that I can take to protect these plants? These plants were also re-potted, before re-potting the infected zebra plant and amaryllis – that is, I was not in contact with the infected soil when I re-potted these healthy plants.
I’m hoping you can help save my plants! Your advice is much appreciated! Please let me know if you would like me to send a picture as well.
Thank you for contacting the Toronto Master Gardeners.
Thrips are very small in size. They measure anywhere from 0.5 mm to 2 mm in length depending on age and species. They’re also thin looking. They have elongated, narrow bodies and are brown or yellowish in color. Some species are black in color. The larvae are bright red or yellowish. These insects feed by puncturing the surface of the plant parts and sucking up the contents. Some species of thrips leave sooty spots of black fecal matter on the leaves.
The first thing you must do is to isolate the infected plants so that the thrips do not move onto your other plants. Thrips damage is worst in hot, dry conditions. The easiest way to remove these insects is to wash them off with a fine spray of water. It’s a good idea to spray your plant again after a few days. If this doesn’t work then you can use insecticidal soap made for indoor plants which is available from your local garden center. Spray every 2-3 days for 4 week. Thrip larvae is on the surface of the soil, so be sure to treat the soil, too. Make sure to read the label carefully and follow the manufacturer’s directions for use.
If this doesn’t work then Neem oil for houseplants is another treatment method. This will not kill them immediately but will cause them to stop feeding so that they will eventually die.
If your infestation is very severe you may have no choice but to dispose of your severely damaged plants.