Good Bugs in the House

By midwinter, my houseplants are getting tired. They miss their native subtropical heat, humidity, and bright light. Winter stress makes them great candidates for attacks from whiteflies, spider mites, and other common houseplant pests. This year instead of spraying the plants mercilessly, I've decided to fight bugs with bugs.

Spreading Beneficials
If you have a large solarium, a greenhouse, or just a good collection of houseplants, spreading beneficial insects is a good alternative to spraying-it's most cost effective if you have a lot of plants. Although beneficial insects are slower to control a pest population, if their release is timed properly, they can keep pests under control all winter. Plus, with modern breeding methods and dispersal technology, releasing some beneficials is as simple as hanging a piece of paper in the plant room.

Choosing Your Insects
Most gardeners know that ladybugs, for example, eat aphids and other harmful insects in the garden. However, the beneficials that work outdoors may not be the best solution for indoor pests. I once released 500 ladybugs in the greenhouse attached to our offices at work, only to find a few days later that the ladybugs had spread throughout the offices-in the bathrooms, crawling up the windows, even hiding out in peoples' desks. With the warm indoor temperatures, the ladybugs thought it was spring and wanted to fly away, not eat the aphids on the lettuce plants in the greenhouse.

The best beneficials to use indoors are those that are less mobile and are targeted to a specific pest.

Whitefly Parasite
I've used whitefly parasite (Encarsia formosa) successfully a number of times in our greenhouse. The very tiny adult wasps parasitize whitefly young and eggs. It's easy to tell if they're working by looking at the undersides of leaves for juvenile whiteflies. Normally the juveniles are translucent; those that have been parasitized are black.

The whitefly parasites are shipped as a paper strip with parasitized whiteflies attached. Hang the strips on your plants and let the hatching wasps go to work. The adult is so small, you'd have to look very diligently to find one. If you're concerned about wasps indoors, don't worry-they're only interested in whiteflies, and don't even notice people. If they manage to finish off the whiteflies, they'll die for lack of food.

Good Mites
Another major pest in our greenhouse is spider mites. They love the dry air of winter and can quickly multiply, causing houseplant leaves to yellow. When infestations are severe, you can see mite webs.

There are a number of mite predators on the market. Beneficial mites attack the spider mites and will subdue their population in a matter of weeks. Beneficial mites are microscopic and come in a vial filled with corncob meal. All you do is sprinkle the meal on the plants and let the mites work. Like the whitefly parasites, they don't harm people and will stay on the plants.

Be Patient
The one possibly negative aspect of releasing beneficials indoors is the need for patience. It takes a few weeks for the beneficials to noticeably start working. And you must avoid spraying pesticides while the beneficials are at work, since they're susceptible to all the same sprays as your pest insects. However, once established, they will work for you and your plants as long as there are pests to be found.

Help beneficials to help you by keeping your plants as healthy as possible. Keep the light, humidity, soil moisture and nutrients at right levels for plant growth. Healthier plants are more resistant to pests, and your tiny helpers will do a better job of keeping their prey in check.

Photograph by Charlie Nardozzi/NationalGardening.com

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