Greenhouse Insect Prevention

Answer: 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 harbor problems. If you receive plants, inspect the newcomers carefully and quarantine them elsewhere for a few weeks before putting them in the greenhouse. Have children wash their 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. At least once a year, scrub and rinse the greenhouse interior from top to bottom with a warm disinfectant soap solution.

• Keep magnifying glasses and/or hand lenses in the greenhouse at all times. Your students can become experts at spotting trouble before it gets out of hand. Be sure they look over the entire plant, particularly on the undersides of leaves.
• Keep air circulating and keep the 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. Avoid watering plant leaves unless humidity is low, and try not to water in the evening.
• Care well for your plants, giving them the recommended amounts of water, fertilizer, and so on. A deficit or excess can stress plants and invite problems. High levels of nitrogen from fertilizer, for instance, can attract aphids which, in turn, can spread diseases.