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Welsh Onion Pests and Bug Damage: Causes & How to Fix It

Holes in the leaves of your welsh onion, tiny insects crowded on the undersides, white flies rising when the plant is shaken, or seedlings cut off overnight. Even when you cannot see the insect, the shape of the damage narrows down the culprit.

Check these first

  • What shape is the damage: round holes, only veins left, white trails, or a pale stippling?
  • Where are the insects or droppings: under the leaves, on new shoots, or at the base?
  • If nothing is visible by day, check at night or early morning for cutworms and slugs.

Most likely causes

From the pests and diseases recorded for this plant, the ones whose symptoms match, most serious first. Symptoms alone rarely confirm a cause, so use the linked page to check the signs and treatment.

Onion Thrips

Fine white stippled scars run in vertical lines along the leaf surface, and the whole leaf eventually turns whitish. Growth stops and both yield and quality suffer.

How to identify and treat: Onion Thrips

Leek Moth

White grazed scars and small holes line the leaf surface, and splitting the leaf reveals larvae inside. Damaged leaves snap easily and die back.

How to identify and treat: Leek Moth

Leafminer Flies

Winding white tunnels run through the leaf with the larva at the head of the mine. Heavy mining turns the whole leaf white and dead, cutting photosynthesis.

General description; not specific to this plant.

How to identify and treat: Leafminer Flies

Other possible causes

  • Root-lesion Nematode — Elongated blackish brown necrotic lesions form on the root surface and fine roots rot away…
  • Root-knot Nematode — The plant wilts in the daytime and does not recover with feeding or watering. Pull it up a…

Other symptoms on this plant

What other growers did about it

A page like this one can tell you what welsh onion pests and bug damage is and what to try. What it cannot tell you is what actually happened to someone who had it on the same plant, at the same point in the season, and what they did next.

Gadenin is a free garden journal built around that. You photograph the plant, tag what you are seeing, and the entries line up by date for each plant you grow.

  • Tag the problem and the app tells you how many other growers have logged the same thing on the same plant.
  • Growers who make their records public can be followed, so you can read what they did and how it turned out.
  • Next season your own entries come back at the same point in the year, so you check the plant before it starts.

Free on iPhone. Recording, tagging and reading public records cost nothing.

Read next

Log when you spotted the pest and what you sprayed or removed by hand. Next year you will know when to start checking.

See what other growers did about it

Log it in the free Gadenin app and tag what you are seeing. Your photos line up by date so you can tell whether it is spreading, and you can see how many other growers have logged the same problem on the same plant, follow them and read what they did next.

Free on iPhone. Android coming later.

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