What's Eating My Onions?
Few pests will touch an onion's pungent leaves — but the two that specialize in them can quietly wreck a bed. Both hide well; here's how to catch them.
The usual suspects
Onion thrips
The signs: Silvery-white flecks and streaks along the leaves that merge into a gray cast; tips brown in heavy years and bulbs stay small.
What it looks like: Slender straw-colored insects, barely a millimeter, tucked deep in the leaf folds at the neck — tap a plant over paper to see them move.
What to do: Hard water sprays into the folds weekly, insecticidal soap or spinosad if they build, and generous watering — drought-stressed onions suffer worst. Clean up debris after harvest.
Onion maggots
The signs: Seedlings yellow, wilt, and pull up with rotting, hollowed bases; older bulbs rot from tunnels that invite soft rot.
What it looks like: White legless maggots in the base; the parent is a small gray fly laying at the soil line in spring.
What to do: Rotate alliums to fresh ground each year, cover new beds through the spring flight, cull and trash every infested plant — never compost them.
Cutworms
The signs: Young seedlings clipped at the soil line in spring.
What it looks like: C-curled soil caterpillars beside the losses.
What to do: Patrol-and-squish after each loss; transplant sturdy seedlings rather than direct-seeding where pressure is high.
When it's not a pest at all
Tips browning in midsummer as bulbs swell is normal maturation. Fuzzy purple-gray blotches mid-leaf are downy mildew; papery white patches with tiny black specks are Botrytis leaf blight — weather diseases, both.
Or just point your phone at it
Snap a photo of the leaf, the bug, or the droppings, and Harold — the advisor built into Homestead Paradise — names what he sees, tells you friend or foe, and what he'd do next. Honest when he's unsure, and careful where it counts.
Put Harold's Eyes on it — free 14-day trial