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Thrips

FAST FACTS - THRIPS
by Nanette Londeree, Master Rosarian

SIGNS

  • Tiny, slender adult insects, less than 1/20 inch long, translucent white or yellowish to dark brown or blackish with long fringe around the margins of their wings
  • Larvae similarly shaped with a long, narrow abdomen and no wings

    SYMPTOMS

    Thrips Damage

  • Stippling on leaf surfaces that may become papery
  • Black specks of feces around stippled leaf surfaces
  • Flower buds that are deformed and fail to open
  • Petals covered with brown streaks and spots
  • Distorted plant parts

    CAUSE

  • One of the species of Thrips, order Thysanoptera, most often Western Flower Thrip (Frankliniella occidentalis)

    OPTIMAL CONDITIONS

  • Many herbaceous ornamentals (impatiens, petunia); vegetables (cucurbits, pepper); fruits (grape, strawberry); some shrubs and trees (rose, stone fruit)
  • Prefer to feed in rapidly growing tissue
  • Spring to early fall; lifecycle may be as short as two weeks during warm weather

    TREATMENT

    Prevention:

  • Maintain good cultural practices and plant to attract natural enemies like green lacewings and minute pirate bugs
  • Keep plants well irrigated and avoid excessive applications of nitrogen fertilizer that may promote higher populations of thrips
  • Control nearby weeds that are alternate hosts of certain thrips
  • Select cultivars with sepals that remain tightly wrapped around the bud until just before blooms open

    Elimination:

  • Knock pests off plants with a spray of water
  • Damage to leaves and blooms may be unsightly but does not usually warrant the use of insecticide sprays
  • No pesticide provides complete control due to thripsí tiny size, great mobility, hidden feeding behavior, and protected egg and pupal stages
  • Narrow-range oil (Sunspray, Volck) and neem oil can be somewhat effective for temporary reduction of populations if applied when thrips are present and damage first appears

    GOOD GUY / BAD GUY?

  • A bad guy if you exhibit roses; mostly a nuisance otherwise

  • The photo of Thrips at the top of the page is by Baldo Villegas from the extraordinary website: http://members.tripod.com/buggyrose/irosepests.htm


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    Last Modified: 08/06/2013