Space, screens, and a twice-weekly walk beat a late bottle

A greenhouse concentrates pests the way it concentrates heat. Closed doors, screened vents, quarantine of incoming plants, and clean media stop more damage than a late soap. Crowding blocks light and airflow and hides the underside of leaves until the bench is a carpet of aphids or mites.

Walk a method: tops, undersides, new growth, roots, sticky cards. Map wet corners and hot ends. Remove infested plants instead of hoping they recover in place. Sanitation between batches is cheaper than treating the next sowing.

If you only notice pests when honeydew shines, you scouted too late.

In this series

• Design the house for the climate that will kill the crop
• Ventilation is life support — trapped sun kills faster than a dry bed
• Prove water, drainage, and backup before you buy a timer
• Moist is not waterlogged — roots need air as much as water
• Space, screens, and a twice-weekly walk beat a late bottle
• Plan backward from harvest; a full green house is not a result