Effective Strategies to Keep Pests Out of Your Greenhouse

Growing plants in a greenhouse provides many benefits, including protection from weather, controlled conditions, and extended seasons. However, greenhouses can also attract a host of unwelcome pests intent on munching your crops. Learning strategies to exclude and deter bugs is key to safeguarding your greenhouse plants.

Common Greenhouse Pests

A wide variety of insects, mites and fungal pathogens may infiltrate your greenhouse in search of food and favorable habitat. Common intruders include:

• Aphids thrips, and whiteflies – These small sucking insects feed on plant sap.

• Caterpillars and beetles – These chewing pests devour leaves and stems.

• Spider mites – These tiny arachnids suck juices from leaves.

• Fungal diseases – These take hold in warm, humid conditions.

• Ants and earwigs – These seek shelter and get transported in on plants

While not all bugs are harmful, major infestations can seriously damage crops. Exclusion is the first line of defense to prevent this.

Physical Barriers to Stop Pests

Here are some ways to physically block pests from entering your greenhouse:

• Seal cracks and crevices – Caulk and seal any gaps in the greenhouse glazing, doors, vents or foundation. These provide entry points for pests.

• Screen vents and openings – Install fine mesh screens on all vent openings. For insects, use mesh with openings smaller than 1/25 inch or 1 mm.

• Double door entryways – Use a small enclosed entry space as a buffer zone between the outside and greenhouse interior to deter flying insects.

• Air curtains – Mounted fans blow a sheet of air across doorways to deter flying insects.

• Sticky traps – Position sticky card traps near doors and vents to catch incoming adults before they reproduce.

Cultural Practices That Deter Pests

Certain greenhouse management practices also help reduce pest problems:

• Remove weeds and debris – These provide shelter for pests around the exterior.

• Disinfect tools and equipment – This prevents diseases and insects from hitchhiking into your greenhouse.

• Keep plants isolated – Quarantine new plants before introducing them to check for signs of pests.

• Remove plant debris – Promptly remove and dispose of expired plants and prune suckers to eliminate pest habitat.

• Manage water – Avoid excess moisture which encourages fungal diseases. Let the soil dry between waterings.

• Promote airflow – Good ventilation and air circulation keeps greenhouse humidity in check.

Using Biological Controls

Natural biological control agents are allies in the fight against greenhouse pests. Consider introducing:

• Predatory insects – Lacewings, ladybugs and parasitic wasps feed on aphids, mites, whiteflies and other prey.

• Predatory mites – Several mite species attack spider mites and thrips.

• Nematodes – These parasitic roundworms provide natural pest control against soil-dwelling pests.

• Bacillus thuringiensis – This natural bacteria kills caterpillars when they ingest it but is safe for humans.

Pest Deterrent Plants

Certain plants naturally repel or confuse insects through smell or appearance. Try incorporating:

• Marigolds – Repels whiteflies, aphids, and other pests
• Basil and garlic – Repel thrips, aphids and flies
• Petunias – Protect vegetables from aphids and beetles

Be Vigilant against Greenhouse Pests

Excluding and controlling pests takes diligence and integrating multiple strategies. Check plants frequently for early signs of infestation. Respond quickly to treat limited outbreaks before they escalate. Consistent monitoring along with proactive prevention will help protect your greenhouse plants from destruction by invasive bugs and diseases.