See what your mesh really stops
Exclusion sizes: published university extension figures. Finer mesh cuts airflow: choose the largest aperture that stops your target pest.
Published exclusion sizes
| Pest (species tested) | Approx. max opening | Primary source |
|---|---|---|
 Western flower thrips (Frankliniella occidentalis) | 0.192 mm | Bethke & Paine 1991 |
 Cotton aphid (Aphis gossypii) | 0.341 mm | Bethke & Paine 1991 |
 Sweetpotato whitefly (Bemisia tabaci group) | 0.462 mm | Bethke & Paine 1991 |
 Leafminer (Liriomyza trifolii) | 0.640 mm | Bethke & Paine 1991 |
When to use this tool
Use it when you know the pest you need to keep out but not the mesh, when you are comparing insect-netting offers with different mesh counts, or when a supplier quotes a "mesh number" and you want the actual opening in millimetres. It answers the practical question behind searches like "what mesh size stops thrips" or "insect netting mesh size".
Common mistakes it helps avoid
- Confusing mesh count with aperture. A "50 mesh" figure depends on thread thickness; the opening in millimetres is what actually excludes an insect.
- Choosing the finest mesh "to be safe". Finer mesh cuts airflow and raises heat and humidity under the cover, which can hurt the crop. The right choice is the largest aperture that still stops your pest.
- Ignoring strain and regional variation. Published sizes are starting points; a local pest population can sit slightly outside them, which is why we confirm per project.
Sources used for exclusion aperture ranges
The aperture values in this visualizer are approximate starting points, not universal guarantees. They are based primarily on Bethke and Paine's laboratory work on insect-screen barriers for glasshouse crops, then cross-checked against extension guidance on greenhouse micro-screening. Final aperture selection depends on pest species or strain, screen construction, installation quality and airflow requirements.
- James A. Bethke and Timothy D. Paine, "Screen Hole Size and Barriers for Exclusion of Insect Pests of Glasshouse Crops", Journal of Entomological Science, 26(1), 169-177, 1991. Reported maximum hole sizes include western flower thrips 192 micrometres, cotton aphid 341 micrometres, sweetpotato whitefly 462 micrometres and leafminer 640 micrometres.
- Michelle L. Bell and James R. Baker, "Greenhouse Screening: Comparison of Materials for Excluding Thrips and Whiteflies", N.C. Flower Growers' Bulletin, Department of Entomology, North Carolina State University, 40(2), April 1995. Cites Bethke and Paine and explains the exclusion-versus-airflow trade-off.
- University of Tennessee Extension, "Insect and Mite Pest Management in Greenhouses", PB1594. Practical examples: leafminers at about 0.025-inch mesh and western flower thrips at about 0.0075-inch mesh (approximately 0.635 mm and 0.191 mm).
- Raymond A. Cloyd et al., Kansas State University MF2892 and University of Missouri Extension IPM1026. Recommend micro-screening for winged aphids, adult whiteflies, thrips and leafminers, while warning that airflow reduction must be compensated.
Related buying guide
For materials, UV treatment and roll formats, see the guide to choosing agricultural netting, or jump to insect netting specifications.
Frequently asked questions
What mesh size stops thrips?
Bethke and Paine (1991) reported about 0.192 mm for western flower thrips, the smallest common target, and University of Tennessee Extension confirms roughly 0.0075 inch. The exact aperture is confirmed against your pest and crop before quoting.
What mesh size stops whiteflies?
Roughly 0.46 mm openings exclude the sweetpotato/silverleaf whitefly (Bemisia tabaci) tested by Bethke and Paine (1991); cotton aphid needs about 0.34 mm. Other species may differ.
Does finer mesh always mean better protection?
No. Finer mesh cuts airflow and raises heat and humidity under the cover, which can hurt the crop and favour disease. The right aperture is the largest one that still excludes your target pest.