Regional Gardening Reports :: National Gardening Association

In the Garden:
New England
February, 2001
Regional Report

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Whitefly parasites come attached to small paper cards and are released by simply hanging the cards on infected plants.

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. However, 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, windows, and even 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 adult flies parasitize whitefly young and eggs. It's easy to tell if they're working by looking at the undersides of leaves where whitefly young live. Whitefly young are normally translucent; whitefly young that have been parasitized are black.

The whitefly parasites are shipped as a paper strip with parasitized whiteflies attached. Just hang the strips on the plants and let the parasites go to work. The small adult parasitic fly is hardly noticeable and definitely not harmful. When all the whiteflies have been killed, the parasite dies 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 yellow leaves on a number of houseplants. When infestations are severe, they will form 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 cornmeal. All you do is sprinkle the cornmeal 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 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.

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