Q: I had many mealybugs on the floors of my house last spring, so I put them outside, waiting for predators to take care of them, or at least I wouldn't have to deal with them for a while. Now it's cold and I know I have to bring them inside. How do I get rid of mealybugs and make sure I don't bring any new mistakes?
A: It can be very difficult to do, but unless your infested plants are especially valuable, monetary or sentimental, the best thing you can do is throw them away.
The mealybugs, which look like small groups of cotton threads, are very difficult to remove. Those you see can be killed with isopropyl alcohol in a cotton swab, but they are also usually in hidden places, such as the crotch of the leaves or in the roots of the plants. They secrete a waxy substance that covers them, forming a layer resistant to the penetration of insecticides. They also lay hundreds of eggs, so they spread quickly. They are not just a cosmetic problem, since they weaken plants by sucking juices. Unless they can be controlled, the plants continue to decrease until the decision to get rid of them is easy, but by that time, it is possible that their other plants are infested.
The best control is to stop the problem ahead of time by checking each new plant for errors. Washing new plants with a hose or in a sink or shower is never too much, but it does not necessarily make your home safe. Look for the signs of insects with each irrigation. Also check around the plants. You can find eggs, or you can see insects heading towards their next victims.
To help control the mealybugs in the plants from which it cannot be separated, or before bringing any other plant from the outside, wash them with a hose. Use a strong spray to eliminate insects. Spray all plant surfaces with insecticidal soap, which is economical and can be found in garden centers. It is a contact insecticide, which means you need to touch the insect, so make sure you go everywhere insects can be, including pots and saucers. You can reuse it indoors, and it can even be used in groceries as herbs that you can grow as houseplants.
Technically, you should slowly move the plants inside so they get used to reducing the light, but it doesn't seem practical. Like some of us, your plants may seem a little sad at first, but they will recover once they get used to being indoors.
More information on insect control in indoor plants can be found at: extension.umn.edu/product-and-houseplant-pests/insects-indoor-plants.
Written by U of M Extension Master Gardeners in St. Louis County. Send your questions to [email protected]