Western Flower Thrips
General Description
Hosts
Many woody and herbaceous plants.
Damage
Apple - White to pink irregular areas called pansy spots develop around egg punctures in young apple fruitlets (Fig. 1), especially of McIntosh, as well as Spartan and Newtown apples.
 |
| Figure 1. Thrips feeding injury to apple ('pansy spot'). (H. Philip) |
Cherry - Thrips laying eggs in the ovary of cherry flowers cause a dimple-like injury to form on mature fruit (Fig. 2). Just as the fruit begins to colour the dimple appears as a bright red spot against the yellow-green background.
 |
| Figure 2. Thrips feeding damage to cherries. (AA-FC) |
Nectarine - Adult feeding and egg laying on young nectarines can severely scar the fruit surfaces, rendering the fruit unmarketable.
Identification
Nymph - Similar to adult except wingless, smaller and yellow in colour.
Adult - Slender, tan to dark brown, 1.2 mm long, with narrow fringed wings (Fig. 3).
.jpg) |
| Figure 3. Western flower thrips adult and nymphs. (Alberta Research Council) |
Life History
Western flower thrips overwinter as adults in protected sites on the ground. In the spring, adults fly to flowers of many plant species where they feed on blossoms and insert eggs into the flower parts. Second generation adults insert eggs into young apple fruitlets during bloom and petal-fall.
Monitoring
There is no practical monitoring method for B.C, however their presence can be detected using a beating tray when the blossoms begin to open.
Management
Cultural Control
Do not mow blooming ground cover from 1 week before bloom until after petal-fall to reduce driving thrips up into apple trees.
Chemical Control
Apply Harvanta at petal fall/husk fall for the suppression of thrips on apple, cherries, and nectarines. Apply Success 480 SC or Entrust between early petal fall and husk fall for control/ suppression of thrips on nectarines (maximum 3 applications per season). Allow 7-10 days between applications. Application of Success or Entrust to apples at petal fall for leafroller control will also suppress thrips and reduce pansy spot on susceptible varieties.
Success or Entrust applied against leafrollers during petal fall will suppress any thrips present, however not before some damage has been done.