How to Protect Onions and Leeks from Thrips Damage

There’s nothing more disheartening than pulling back leek leaves or inspecting onion tops only to find them streaked, silvery, and starting to curl. Chances are, thrips have moved in. Tiny, fast-moving pests that suck the sap from your alliums, causing stunted growth, distorted leaves, and reduced yields. But don’t panic. With the right approach, we can protect our onions and leeks from thrips damage and keep our harvests healthy and strong.

Know What You’re Up Against

Thrips are minute, slender insects that feed by puncturing plant cells and sucking out the contents. On onions and leeks, they cause silvering, curling, and streaking of leaves. You’ll usually find them hidden deep in the folds of foliage, and they’re most active in warm, dry weather.

Start with Healthy Plants

Strong plants are more resilient. We start with healthy sets or robust seedlings, planted in well-drained soil enriched with compost. Thrips tend to target stressed or nutrient-deficient crops, so we keep our alliums well-fed with a balanced organic feed and watered during dry spells to avoid drought stress.

Use Fine Mesh Netting

A simple but effective barrier, fine mesh netting stops adult thrips from reaching your crops. We cover our onions and leeks from planting day with insect-proof mesh, supported on hoops to allow airflow and avoid damaging the leaves. It’s a low-effort step that dramatically reduces infestations.

Interplant and Diversify

Thrips don’t love strong-smelling herbs, so we interplant onions and leeks with basil, thyme, or even chamomile to throw them off the scent. A more diverse planting scheme also helps attract natural predators like ladybirds and lacewings, which feed on thrips larvae.

Blast Them Off with Water

If we catch an early infestation, a firm spray of water directly into the leaf folds can knock thrips out of their hiding places. We do this in the early morning so the plants dry quickly and don’t invite fungal diseases. It’s simple, safe, and surprisingly effective with regular repetition.

Bring in the Beneficial Bugs

We don’t fight pests alone, Orius bugs and lacewing larvae are brilliant natural enemies of thrips. If the population starts to climb and our garden ecosystem needs a boost, we release beneficial insects into the plot. It’s an especially handy trick for polytunnel growers or densely planted beds.

Harvest Promptly and Store Well

When onions and leeks are ready, we harvest promptly. Damaged plants can attract more pests, and thrips can continue feeding even in storage. We cure onions thoroughly and store them in dry, well-ventilated conditions to prevent problems from spreading post-harvest.

Thrips might be hard to spot, but their damage is unmistakable, and frustrating. Thankfully, a mix of smart planting, careful observation, and a few natural tricks can keep them under control. With a little persistence, we can protect our onions and leeks from thrips damage and enjoy a strong, clean harvest.