Thrips, Thysanoptera, are plant pests that can affect both indoor and outdoor plants. They are tiny, slender-bodied insects with narrow, fringed wings and rasping mouth parts that suck plant juices. Their actions can cause stippling and scarring on leaf surfaces, as well as papery leaves and misshapen buds. Many species of thrips can affect plants, including citrus thrips, onion thrips, bean thrips, greenhouse thrips and western flower thrips. A few techniques can help you kill thrips and protect your plants.
Set out yellow sticky traps around plants to capture the thrips if there are only a small number of the insects
Apply natural predators of thrips if there are a large number of the insects. Minute pirate bugs or predacious mites are natural enemies of thrips and will control the population. Green lacewings and predatory wasps are other useful predators of the thrip. These beneficial insects are available at garden centres.
Apply insecticidal soap or neem oil spray for temporary help to control the thrip population. These products are safe to use on indoor plants.
Spray spinosad, imidacloprid or acephate onto plants to treat serious infestations. Apply according to label directions, and be sure not to apply more often than recommended on the label, as pests can become resistant.
Black, varnish-like spots on leaves are the excrement of thrips. It can last on leaves for some time after the thrips have left. For outdoor plants, use reflective mulch that confuses plant insects and helps to keep them away.
Be aware that using chemical pesticides also kills beneficial insects that help to control thrips. Use only as a last result and only for the time needed to control the insects.