Trouble with Aphids in Your Greenhouse?

By Betsy Woodworth

Aphids have a tendency to settle into your greenhouse as summer closes and fall settles in. Vegetation in your greenhouse provides an appetizing alternative to the outside garden. Aphids are a common greenhouse problem, and not the easiest to combat.

The first step in dealing with aphids in your garden greenhouse is to make sure you carefully monitor plants you choose to transplant into your greenhouse. Plants selected for your greenhouse should be healthy and vigorous. In addition, you should spray them down with your garden hose to knock off any hitchhikers. If the plant has an obvious insect infestation, do not bring it into your greenhouse without more drastic measures. You can spray it with an insect control spray, or enclose it with a plastic bag in which you place an insecticide strip for two or three days. After taking your plants out of the treatment bag, hose them down before transplanting them to your greenhouse.

Minimal measures - Aphids can sometimes become established no matter how careful you are. If this happens there are several alternative paths you can take. If you do not want to use any insecticides in your greenhouse environment, you have a couple options. Hosing down infected plants with a powerful stream from your garden hose can be effective for a while. This may be the best option If you plan on closing down your greenhouse soon. Some hobby greenhouse gardeners choose to shut their greenhouse down for anywhere from 2-4 months in the winter allowing nature to take its course and freeze out insect pests. Diatomaceous earth is effective if you want a little more aggressive natural control. Sprinkle this powder on and under leaves of effected plants. This can be an effective control if you catch the problem early and have isolated insects in one part of your greenhouse,

Another way to control your aphid problem is to use a fast acting insecticide that is safe for using on vegetable gardens. There are several varieties out there that are "garden safe." Check your local garden center or hardware store for alternatives. Most of these involve an organic insecticidal soap that takes care of aphids, or at least significantly reduces their number. You can also make your own version of this by mixing a tablespoon of liquid dish detergent with water in a quart sprayer. The soap coats the aphids and reduces their numbers. You have to spray every day for best results, paying particular attention to the underside of leaves of infected plants.

Eat or be eaten - biological controls - another alternative to aphid control are biological controls, such as lacewings, ladybugs and midges. Several companies provide these predators for your greenhouses. If using this approach, be sure to limit your use of insecticidal spray, as it will kill off your predator population, as well as your pests.

There is never a foolproof control for aphids, but using a combination of the above controls should help you enjoys your greenhouse through fall and winter. - 30446

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