25 Mesh vs 40 Mesh: Which One Is Better for Vegetables & Berries?

Editor’s Note

This article is part of our Insect Netting Hub Guide, which compares mesh sizes, exclusion performance, ventilation effects, and crop suitability across different growing systems.

Visit the Hub to explore more technical guides and decision tools for growers.

Introduction

Why Growers Compare 25 Mesh and 40 Mesh

Among all mid-density insect nets, 25 mesh and 40 mesh are the most commonly used for vegetables and berry crops. They are close enough in mesh number to cause confusion, yet different enough in performance to dramatically affect:

• Pest exclusion reliability
• Ventilation and microclimate
• Disease pressure
• Yield and fruit quality
• Crop-specific suitability

Both meshes work well—but not for the same pests and not for the same climates. Choosing between them requires understanding how mesh aperture interacts with insect morphology, especially thorax width.

This guide compares the two meshes using field experience and scientific data from your PDF, focusing on flea beetles, diamondback moth, leafminers, whiteflies, aphids, and Drosophila (SWD)—the most important pests for vegetable and berry growers.

25 Mesh vs 40 Mesh: Quick Technical Overview

Mesh	Typical Aperture (mm)	Target Pest Size	Ventilation	Typical Use
25 Mesh	0.60–0.70 mm	≥ 0.60 mm insects	High	Outdoor vegetables, heat-prone regions
40 Mesh	~0.40 mm	≥ 0.35–0.40 mm insects	Medium	Greenhouses, berries, virus vectors

At first glance, 25 mesh looks sufficient for most vegetables—but berry crops and greenhouse vegetables often require finer protection.

To understand why, we need to examine real insect morphology data.

Pest Morphology: How 25 Mesh vs 40 Mesh Performs Against Key Pests

(Using thorax width → aperture threshold → exclusion probability)

Flea Beetles — Thorax 600–800 µm

25 Mesh Verdict: Excellent Aperture 0.60–0.70 mm matches flea beetle thorax width almost perfectly.

• 25 mesh physically blocks flea beetles
• No need for 40 mesh
• Better ventilation → lower heat stress for leafy greens

40 Mesh Verdict: Unnecessary (Over-spec)

While 40 mesh blocks flea beetles, it offers no meaningful advantage.

Best choice:25 Mesh

Diamondback Moth — Thorax > 1.0 mm

25 Mesh Verdict: Fully Effective Diamondback moth adults are large enough that 25 mesh reliably prevents their entry.

40 Mesh Verdict: Also Effective 40 mesh offers no exclusion advantage for this pest.

• Best choice:25 Mesh（open field ）
• Best choice:40 Mesh（The high temperature and low wind outlet in the greenhouse are not suitable, but not necessary.）

Leafminers — Thorax ~600 µm

Leafminers fit into the medium-sized group similar to flea beetles.

25 Mesh: Blocks most adults; adequate for field crops.

40 Mesh: More reliable under high pressure.

Recommendation:

• Field vegetables → 25 mesh is usually enough
• Greenhouse vegetables → 40 mesh preferred

Aphids — Thorax > 340 µm

40 Mesh Advantage Appears Here

• 25 mesh can reduce aphid entry but not reliably
• 40 mesh aperture (~400 µm) aligns closer to aphid chest width
• Aphids transmit dangerous viruses → reliability > ventilation

Recommendation:

• Virus-sensitive crops (peppers, tomatoes) → 40 mesh
• Leafy greens in hot climates → 25 mesh

Whiteflies — Thorax 239–290 µm

This is where 25 mesh becomes insufficient.

25 Mesh: Aperture too large → whiteflies pass easily in both field and greenhouse settings.

40 Mesh: Provides partial to strong exclusion depending on yarn diameter → far superior to 25 mesh.

For crops like:

• Tomatoes
• Peppers
• Eggplants
• Strawberries

40 mesh significantly lowers whitefly and virus pressure (TYLCV / ToCV).

SWD / Drosophila— Thorax 1.0–1.4 mm

Extremely critical for berries

Berry crops such as:

• Blueberry
• Raspberry
• Strawberry
• Blackberry

are heavily affected by SWD (Spotted Wing Drosophila).

Although SWD is larger than its cousin fruit flies, their flight behavior = crawling & probing, not simply flying straight.

So netting must be both small enough AND stable enough to prevent probing penetration.

25 Mesh:

• Aperture too large for reliable SWD exclusion
• High risk during harvesting cycles
• Not recommended for berries

40 Mesh:

• Offers more reliable SWD protection
• Matches berry industry standards

Best choice for berries:40 Mesh

25 Mesh vs 40 Mesh: Performance Summary by Pest Category

Pest	Thorax Width	25 Mesh	40 Mesh	Best Choice
Flea beetles	600–800 µm	✔ Excellent	✔ Good	25 mesh
Diamondback moth	>1,000 µm	✔ Excellent	✔ Excellent	Both (25 mesh preferred outdoors)
Leafminers	~600 µm	✔ Good	✔ Better	Depends on climate
Aphids	>340 µm	△ Medium	✔ Good	40 mesh
Whiteflies	239–290 µm	✘ Poor	✔ Good	40 mesh
SWD / Drosophila	1,000–1,400 µm	△ Unreliable	✔ Reliable	40 mesh

Ventilation & Microclimate: The Practical Difference Between 25 and 40 Mesh

Ventilation Loss

25 mesh has:

• Higher porosity
• Lower airflow resistance
• Less temperature accumulation

40 mesh has:

• Moderate porosity
• Noticeable temperature increase
• Higher risk of condensation & fungal disease if used in hot climates

Climate Suitability

Climate	Best Mesh	Reason
Hot / Tropical	25 mesh	Ventilation is critical
Warm Greenhouse	40 mesh	Exclusion of whiteflies + aphids
Cool Temperate	40 mesh	Lower ventilation needs
Berry Tunnels	40 mesh	Essential for SWD protection

Crop-Based Recommendations（Vegetables & Berries）

Vegetables：Open-field cultivation

Best Mesh: 25 Mesh

Reason:

• High airflow
• Adequate protection against flea beetles, diamondback moth, leafminers
• Low heat stress

Crop list:

• Lettuce, spinach, leafy greens
• Cabbage, broccoli, cauliflower
• Outdoor cucumber, squash, melon

Vegetables：Facility greenhouse cultivation

Best Mesh: 40 Mesh

Reason:

• Whiteflies & aphids become dominant pests
• Virus pressure higher
• Microclimate manageable with side vents

Crops:

• Tomatoes
• Peppers
• Eggplant
• Greenhouse cucumbers

Berries(Blueberry/Strawberry/Raspberry)

Best Mesh: 40 Mesh（Highly recommended）

Reason:

• SWD exclusion
• Berry value is high → risk intolerant
• Longer-season crops → sustained protection required

25 mesh Not recommended for any berry crops.。

Cost & Longevity Considerations

Factor	25 Mesh	40 Mesh
Material cost	Lower	Higher
UV life	Similar	Similar
Ventilation load	Lower	Higher
Disease risk	Lower	Higher
Pest protection	Medium	High
Use cases	Outdoor vegetables	Greenhouses, berries

Final Decision Framework

1. Target pests?
   1. Flea beetles / moths → 25 mesh
   2. Aphids / whiteflies → 40 mesh
   3. SWD → 40 mesh
2. Crop type?
   1. Leafy greens / cole crops → 25 mesh
   2. Tomatoes / peppers → 40 mesh
   3. Berries → 40 mesh
3. Climate?
   1. Hot → 25 mesh
   2. Cool / greenhouse → 40 mesh
4. Disease pressure? High → use finer mesh

Final Recommendations

25 Mesh (Best choice for open-field vegetables)

• Best ventilation
• Effective for large and medium pests
• Ideal for hot climates
• Great for leafy greens and brassicas

40 Mesh (Standard selection of berries and greenhouse vegetables.)

• Strong protection against aphids & whiteflies
• Essential for berries (SWD)
• More stable exclusion performance
• Better for high-value crops

Simple rule:

→ If your main pests are flea beetles & moths = 25 Mesh

→ If your main pests are whiteflies, aphids, or SWD = 40 Mesh

Need help matching mesh size to your crop and pest pressure?

Contact our agronomy team or explore our full Insect Netting Guide for data-driven tools and mesh comparison charts.

FAQ-25 Mesh vs 40 Mesh

1. Is 25 mesh enough to protect against flea beetles?

Yes. Flea beetles have thorax widths between 600–800 µm, which is larger than the 0.60–0.70 mm aperture of 25 mesh. This makes 25 mesh fully effective for excluding flea beetles in both open-field and tunnel-grown vegetables.

2. Why is 40 mesh recommended for tomatoes, peppers, and cucumbers?

Because these crops suffer from whiteflies and aphids, which transmit serious viral diseases. 40 mesh reduces virus-vector entry and provides more reliable long-term exclusion compared with 25 mesh.

3. Can I use 25 mesh for strawberries or blueberries?

Not recommended. Berry crops require stable exclusion against SWD, which has probing and crawling behavior that bypasses 25 mesh. 40 mesh is the standard for commercial berry farms.

4. Will 40 mesh increase temperature inside the greenhouse?

Yes, airflow resistance is higher compared with 25 mesh. This can increase temperatures by 1–3°C depending on climate and ventilation design, so growers may need larger vents or forced ventilation.

5. Is 40 mesh necessary for controlling diamondback moth?

No. Diamondback moth adults are large, so 25 mesh already blocks them effectively. Mesh choice should instead be based on other pests, crop sensitivity, and climate factors.

6. Which mesh size is better for virus prevention?

40 mesh is superior because it better blocks aphids and whiteflies, which are major vectors for TYLCV and other viral diseases. Virus-sensitive crops benefit significantly from the finer mesh.