WSU Extension


Onions, Garlic
Basal rot 
Downy mildew 
Gray mold 
Neck rot 
White rot 
Onion maggot 
Onion thrips 

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Caption: Onion thrips
Photo by: Unknown
Onions, Garlic : Onion thrips
(revision date: 3/22/2021)

Onion thrips are tiny, slender insects about 1/16" long. They are yellowish to dark in color, depending on age. They feed on tender inner leaves, causing longitudinal silvery to white mottling or streaking along the leaves. Often, tiny black specks of frass (excrement) may be present. The mottled areas later turn yellow or brown. Damaged leaves may wither and droop. Severe damage may kill seedlings and reduce yield. Thrips are also found on debris of the host plants and on weeds.
Management Options

Non-Chemical Management
  • Heavy rain or sprinkler irrigation may help control thrips populations.
  • Control weeds in and around the garden.
  • Remove piles of plant debris, particularly culled onion bulbs and tops.
  • Natural enemies including predacious thrips help control populations of plant-feeding thrips. Avoid use of broad-spectrum insecticides which kill beneficial insects.
Select non-chemical management options as your first choice!

Chemical Management

Apply to green onion according to label instructions when thrips or early damage is first observed. Soaps may require several applications.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bug Buster-O [Organic]
    Active ingredient: pyrethrins  |  EPA reg no: 1021-1771-54705
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium salts of fatty acid  |  EPA reg no: 42697-60
  • Safer Brand Insect Killing Soap with Seaweed Extract II [Organic]
    Active ingredient: potassium salts of fatty acid  |  EPA reg no: 42697-59
  • This list may not include all products registered for this use.

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Caption: Onion thrips
Photo by: Unknown