Editor’s Note
Mesh Size • Ventilation • Pollination • Crop Safety • Practical Use
This article serves as an introductory guide in our Insect Netting Knowledge Series, covering the essential concepts growers should understand before choosing and using insect netting.
For deeper technical details, crop-specific strategies, and complete system recommendations, please visit the Insect Netting Hub Page.
Introduction
Insect netting has become a cornerstone of modern high-value vegetable and berry production.
However, many growers struggle with real-world questions:
- Which mesh size should I choose?
- Will insect netting make my greenhouse hotter?
- Can bees still pollinate?
- Is 75 mesh always better than 50 mesh?
- How long does netting last?
This comprehensive FAQ consolidates all key topics into one article, offering science-based, field-tested answers in a clear and practical way.
What actually determines insect-exclusion performance? Mesh size or aperture?
Most growers assume that a higher mesh number means better protection.
This is only partially true.
The real barrier is the aperture (micron/mm), not the mesh number itself
Mesh only tells you how many openings are in one inch of fabric. It does not account for yarn diameter. If the yarn becomes thicker, the aperture becomes smaller—even at the same mesh number.
Therefore, two key parameters determine exclusion performance:
- Aperture width (mm / µm) – the physical opening insects must pass through
- Insect thorax width – the minimum rigid dimension of an insect’s body
For example:
- Western flower thrips have thorax widths as small as 0.19–0.25 mm → require fine apertures (≈0.17–0.20 mm)
- Whiteflies are larger (≈0.24–0.29 mm) → effectively stopped by 40–60 mesh
- Aphids and leafminers are even larger → 40 mesh is sufficient
Conclusion:
Choosing insect netting based only on “mesh number” is unreliable. Always evaluate the actual aperture size relative to the target pest.
Does insect netting reduce ventilation or increase greenhouse temperature?
Yes—this is one of the biggest trade-offs in protected agriculture.
Finer nets significantly reduce ventilation
Research on greenhouse airflow has demonstrated that as mesh becomes finer:
- Airflow resistance increases
- Natural ventilation can drop by 35–50% as mesh gets denser
- Internal temperatures rise by 1–3°C under sunny conditions
- Humidity increases and condensation persists longer
This is the root cause of secondary problems such as:
- Botrytis (gray mold)
- Downy mildew
- Leaf mold
- Increased heat stress
When is high-density netting NOT recommended?
- Hot summer climates
- Greenhouses relying solely on natural ventilation
- Crops sensitive to heat (leafy greens, peppers)
- Structures without fans or evaporative-cooling systems
Strategies to improve ventilation
You can reduce microclimate problems by:
- Using rectangular-aperture nets (e.g., 0.25 × 0.8 mm)
- Increasing vent area by 20–30%
- Installing circulation fans
- Choosing photoselective colored nets (better airflow at similar pest control levels)
Can bees pass through insect netting? Will netting interfere with pollination?
Whether bees can enter depends entirely on the aperture.
Bees cannot enter 17–25 mesh nets, even though apertures are often larger than 1.0 mm, because bee body width is about 3–4 mm.
However, very small wild bee species might pass through larger apertures within this range.
Examples:
- 17–25 mesh nets
- Apertures > 1.0 mm
Suitable for crops like:
- Melons
- Watermelons
- Pumpkins
- Cucurbits requiring open-field pollination
Bees are blocked by medium and fine netting
- 40–50 mesh and above prevents bee entry
- Nets for whiteflies or thrips also block natural pollinators
How to manage pollination under insect netting?
You can choose one of three approaches:
A. Use parthenocarpic (self-fruiting) varieties
Best for cucumbers → full-season netting becomes possible.
B. Place commercial bee hives inside the net house
Common in tomato, pepper, and strawberry production.
C. Temporary net removal during flowering
Works but increases pest invasion risk.
Conclusion:
Medium and fine insect nets always restrict natural pollination unless bees are placed inside the structure.
Can insect netting increase disease pressure?
Indirectly, yes.
Why fungal diseases increase under dense nets
Reduced airflow leads to:
- Higher humidity
- Slower leaf drying
- Micro-condensation on foliage
- Warmer temperatures in the early afternoon
These conditions strongly favor:
- Botrytis
- Powdery mildew
- Downy mildew
How to avoid this problem
- Improve air circulation
- Avoid overhead irrigation in the evening
- Increase vent opening size
- Consider colored nets with better airflow (grey/silver/red)
How should growers choose between 40, 50, 60, and 75 mesh?
Here is a practical breakdown:
40–50 mesh: the global standard
Effective against:
- Aphids
- Whiteflies
- Small flies
- Virus vectors in tomato and pepper crops
Advantages:
- Good balance of pest control and ventilation
- Suitable for most vegetables
60 mesh: intermediate protection
Used when:
- Whitefly pressure is high
- Temperatures are moderate
- Virus transmission risk is severe
75 mesh: for thrips exclusion only
This is the only mesh fine enough for complete thrips exclusion.
But:
- Ventilation loss is severe
- Heat buildup is high
- Fans or forced ventilation are required
Conclusion:
75 mesh should be reserved for high-value crops and thrips-intense regions.
For general vegetable production, 50 mesh is optimal.
Does the color of insect netting affect its performance?
Surprisingly, yes—color plays a large role in insect behavior and microclimate.
Red insect netting (best for thrips suppression)
Studies have shown that red netting:
- Disrupts thrips visual orientation
- Reduces landing behavior
- Provides protection even with larger apertures
- Maintains better ventilation than ultra-dense nets
- Can reduce insecticide use by 25–50%
Ideal for:
- Onions, leeks, and scallions
- Thrips-prone environments
- Hot climates where dense mesh causes overheating
Grey or silver netting
Benefits:
- Reflects heat and UV light
- Reduces crop temperature
- Repels aphids and whiteflies
- Ideal for summer vegetable production
Black and white nets
- Black nets: lower light, cooler canopy
- White nets: highest light transmission
They offer no insect-repellent effect but are useful for microclimate tuning.
How long does insect netting last? How should it be maintained?
Expected lifespan
- Temperate climates: 5–10 years
- Tropical climates: 3–5 years
Depends on:
- UV stabilizer quality
- Cleaning routine
- Wind load and dust accumulation
Cleaning recommendations
To maintain airflow:
- Wash nets at least once per year
- Use low-pressure water
- Use mild, neutral detergents
- Never use bleach, which damages UV stabilizers and causes rapid brittleness
- Clean from the inside outward to avoid pushing debris into the structure
What installation mistakes cause most failures?
Poor sealing
Even a 1 cm gap can compromise the entire system.
Correct installation requires:
- Burying edges 30–50 cm into soil
- Tight clipping with profiles and wiggle wires
- Zero gaps around ventilation fans, motors, and pipes
- A double-door vestibule for worker entry
- Sticky traps inside the vestibule for monitoring
Covering without first sanitizing the soil
If thrips pupae, leafminer larvae, or fungus gnat populations are already in the soil, covering the structure creates a “protected breeding chamber.”
Best practice:
- Perform soil solarization or sanitation before installing netting
Final Recommendations
To maximize success with insect netting:
Match aperture size to the target insect
Mesh number is not enough—thorax width determines the true requirement.
Consider microclimate effects
Choose a net density based on climate, crop sensitivity, and ventilation capacity.
Integrate netting with a full system
Includes pollination strategy, ventilation support, soil sanitation, and proper sealing.
When these principles are followed, insect netting becomes one of the most powerful, sustainable, and cost-effective tools in modern crop protection.
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