Insect netting only works if the holes are smaller than the insect. That sounds obvious, until you discover the pest you bought it for slips straight through a mesh that a bigger bug couldn’t. The fix is to choose the mesh by pest size, not by the product photo — and to understand that finer mesh costs more and lets through slightly less air and light. Here is the mesh-size method we use to spec insect net for gardens, greenhouses and farms.
Two specs get confused constantly. GSM is the weight and strength of the yarn; mesh size is the size of the hole. A heavy 80 gsm net with 2 mm holes will stop a moth but not a thrip, while a light 40 gsm net with 0.3 mm holes stops both. For insect exclusion the mesh size is the spec that matters, and it is usually quoted two ways: as a hole measurement in millimetres (0.8 mm, 1 mm), or as a mesh count — the number of holes per inch (40 mesh, 50 mesh). The higher the mesh count, the smaller the hole.
| Target pest | Mesh to use |
|---|---|
| Birds (kept off seedlings) | 1/2″–1″ (12–25 mm) bird net |
| Butterflies & moths (cabbage white, leek moth) | 0.8–1 mm fine mesh |
| Carrot fly, onion fly, aphids | 0.6–0.8 mm fine mesh |
| Whitefly, thrips, leaf miners | 50 mesh (≈0.3 mm) ultra-fine |
The rule of thumb: butterflies and moths = 1 mm or finer; whitefly and thrips = 50 mesh (0.3 mm). If you aren’t sure which pest you have, err finer — an ultra-fine mesh still lets light, water and air through, so over-specifying is safer than under-specifying.
In an open vegetable garden, insect netting is usually laid over hoops or draped directly on the crop and pegged down, so the priorities are fine mesh, light weight, and edges you can bury. For carrots, brassicas and leafy greens, a 0.8 mm fine mesh keeps out carrot fly, cabbage white butterfly and aphids while the plants grow.
Inside a greenhouse, the same net does a different job — it screens vents and doors so pests can’t fly in while the crop grows unprotected. Here you want a mesh fine enough for the smallest pest in your area (whitefly is the usual culprit), but you also need to keep air moving in a humid structure. A 50-mesh net over vents blocks whitefly and thrips while still ventilating, and it lasts longer than soft fleece.
A perfectly sized mesh fails the moment there is a gap at the bottom. Install it right and the net does its job for a full season:
Cheap insect netting frays at the cut edge and disintegrates under UV within a season or two. Quality insect netting is knitted from UV-stabilized HDPE with finished, reinforced edges, so the holes stay uniform and the net keeps its strength for 3–5 years outdoors. Look for a net that holds its mesh shape after cutting, and rinse dust off periodically so the fine holes don’t clog. For the full story on why some nets tear and others don’t, read our guide on insect netting that doesn’t fray.
If you need a specific width, mesh count or roll length — or a net that also blocks sun — tell us your crop and pest and we will knit it to your exact specification.
Read more in our insect netting for vegetable gardens.
Whitefly is tiny, so you need an ultra-fine net — 50 mesh, about 0.3 mm holes. Anything coarser and the whitefly walks straight through.
Yes. Cabbage white and other butterflies and moths need only 0.8–1 mm mesh to be excluded. Reserve 50 mesh for the smallest pests like whitefly and thrips.
Only slightly. Even 50-mesh net lets the large majority of light, water and air through — far more than a solid row cover. It just stops the insects.
Yes — a 0.8 mm mesh works for both. Use it over garden hoops, and to screen greenhouse vents and doors. In humid greenhouses, keep some ventilation so air still moves.
Match the mesh to the smallest pest you have: 1 mm for butterflies and moths, 50 mesh (0.3 mm) for whitefly and thrips — and bury the edges so nothing crawls under. Tell us your crop and pest and we will knit the right insect netting to your size.
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