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Ministry of Agriculture, Food and Rural Affairs

Western Flower Thrips

Adult Female Western Flower Thrips First Instar Western Flower Thrip Larva Adult Female Western Flower Thrips Second Instar Western Flower Thrips Larvae Western Flower Thrips Larva

Click to enlarge.

Beginner

Scientific name: Frankliniella occidentalis

Identification:

  • Thrips have sucking-rasping mouth parts and cause tissue damage when they feed on the leaves or fruit.
  • Feeding on the underside of leaves results in spots or silvery/bronze patches.
  • On fruit, damage often shows up in patches or where fruit touch each other, resulting in faint rings of scarring.
  • They can also damage flowers.

Period of activity: In Ontario, both adults and nymphs overwinter on winter grains, clover and alfalfa. They migrate into vegetable fields as the weedy roadsides dry down and the winter wheat and alfalfa are harvested.

Scouting notes: Thrips are often found in the flowers, but may also be present on the underside of leaves, on fruit, or at the growing point. Plantings near greenhouse tomato, ornamental or bedding plant production are at highest risk of virus transmission.

Thresholds: No established thresholds. Thrips feeding on tomato is not generally a concern, but they can transmit Tomato Spotted Wilt Virus.


 

Advanced

Scientific Name: Frankliniella occidentalis

Identification: Thrips have sucking-rasping mouth parts and cause tissue damage when they feed on the leaves or fruit.  Feeding on the underside of leaves results in spots or silvery/bronze patches. On fruit, damage often shows up in patches or where fruit touch each other, resulting in faint rings of scarring. They can also damage flowers.

Thrips are small (<3-mm long), soft-bodied insects. Adult thrips have straw-brown bodies and four wings fringed with hairs. Nymphs are smaller, wingless and pale white in colour.

Biology:  Western flower thrips have a very wide host range, including many crop and weed species.

Females insert eggs into the leaf tissue. Development form egg to adult requires from 10 to 30 days, depending on temperature. Once mature, females begin to lay eggs. The females reproduce asexually (without mating).  Consequently, increases in the thrips population can occur very rapidly, especially during periods of hot, dry weather. There are several overlapping generations per year.

Period of activity: In Ontario, both adults and nymphs overwinter on winter grains, clover and alfalfa. They migrate into vegetable fields as the weedy roadsides dry down and the winter wheat and alfalfa are harvested.

Scouting Notes: Thrips are often found in the flowers, but may also be present on the underside of leaves, on fruit, or at the growing point. Plantings near greenhouse tomato, ornamental or bedding plant production are at highest risk of virus transmission.

Thresholds:  No established thresholds. Thrips feeding on tomato is not generally a concern, but they can transmit Tomato Spotted Wilt Virus.

Management: There are no good management options for thrips or Tomato Spotted Wilt Virus in tomatoes. Heavy rainfall is effective in knocking thrips off the plant for a short time.