Pests & Diseases

When trying to keep unwanted visitors under control, the first step is to recognize the enemy

In general, there will be attempts by other organisms to colonize the greenhouse paradise you have created. After all, if you were a whitefly or an aphid, wouldn't you rather spend the winter in a warm, moist, verdant spot than in a hard egg under a frozen log? When dealing with pest problems, take heart in the fact that plants often survive pest and disease attacks and that such events can lend another dimension to your students' investigations.

Prevention: The Best Medicine

Healthy plants are the best defense against greenhouse pest and disease problems.

Here are some tips to help you prevent problems before they start:

• Keep it clean! Promptly dispose of all trash, plant parts, diseased plants, and plants past their prime so they won't invite problems.
• Inspect plants carefully and quarantine the newcomers for a few weeks before putting them in the greenhouse.
• Have children wash hands with soap and water after handling diseased plants.
• Make sure your hose doesn't become a disease spreader; keep it from direct contact with plants and keep the nozzle off the floor.
• Start with fresh planting media each season.
• Scrub and rinse the greenhouse interior from top to bottom with a warm disinfectant soap solution at least once a year.
• If your greenhouse is empty during the winter, you may want to do a "freeze-out"—let the inside temperature plunge to wipe out remaining pests.
• Keep air circulating and plants dry. High humidity (above 70 percent) and stale air encourage many pests and diseases. Good ventilation and even small circulating fans can make a big difference.
• Give your plants the recommended amounts of water and fertilizer. A deficit or excess can stress plants and invite problems.

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