Greenhouse Pepper Problems: Heat Stress, Yellowing, and Pest Management

Diagnosing Yellow, Droopy Greenhouse Peppers

Six to eight-inch pepper seedlings turning yellow and drooping in a greenhouse typically signal environmental stress—most commonly excessive heat and/or nutrient deficiency.

Temperature Control Is Paramount

Peppers thrive at 70-80°F with moderate humidity. Greenhouses often exceed 95°F on sunny days, causing heat stress that manifests as yellowing, wilting, and blossom drop. Install:

• Automatic vent openers triggered at 85°F
• Shade cloth (30-40%) for afternoon sun
• Circulation fans to prevent hot pockets

Water and Fertilizer Balance

Overwatering in hot conditions suffocates roots. Water only when the top inch of media is dry. Apply a balanced organic liquid fertilizer (e.g., 3-3-3) at half strength weekly. Avoid high-nitrogen formulas that promote soft, pest-attractive growth.

Pest and Disease Scouting

Check leaf undersides daily for spider mites (fine webbing, stippling) and aphids. Yellow sticky traps monitor whiteflies. If mites are present, spray neem oil or insecticidal soap every 5-7 days, covering leaf undersides thoroughly.

Soil-Borne Pathogens

Recurring issues in the same greenhouse suggest fungal buildup (Fusarium, Verticillium). Solarize beds between crops: cover moist soil with clear plastic for 4-6 weeks in summer heat. Rotate to non-solanaceous crops annually.

Address heat first—it's the most common greenhouse pepper killer. Once temperatures stabilize, nutrition and pest management become more effective.