Thrips

Members of the order Thysanoptera, thrips incorporate more than 6,000 species and can become serious pests in indoor, outdoor and greenhouse settings. In general, thrips are not host plant specific; however; specific species such as onion thrips and tobacco thrips prefer feeding on plants in specific families. Thorough and regular plant inspection is the first and biggest step to take in controlling a thrips infestation.

Life Cycle:

Thrips' life cycle consists of five life stages: egg, larval, prepupal, pupal and adult. The full cycle can take up to 30 days to complete, but will shorten in higher temperatures. Adult thrips lay their eggs directly into plant tissue giving them a place to overwinter come fall and a hatching location surrounded by food sources for the larvae. Once hatched, the larvae feed voraciously on new growth as they prepare to drop to the soil and pupate. After feeding as larvae, thrips develop into their prepupal and pupal stages from which they hatch into wingless nymphs. The nymphs molt two or more times and become winged adults ready to mate. Thrips can go through as many as 12-15 generations per year in warm climates.

Damage:

With each stage after hatching able and willing to feed on plant tissue, thrips can cause extensive damage in a short period of time. Thrips damage typically shows up as stippling, silvering of the leaves, or discolored patches on the leaf surfaces, but will also be present feeding on pollen. The discarded pollen and frass can be a major issue for orchid, violet and other ornamental growers as the buildup is unsightly and can reduce flower longevity. While thrips can have a significant impact on cosmetic appearance, they rarely threaten a plant's survival unless they vector a bacterial, fungal, or viral disease.

Thrips Control:

Early monitoring of suspected target plants is the first that should be taken. Thrips will be much easier to control if treated while the population is still developing. If you suspect thrips have come into your growing area, gently shake foliage/flowers over a piece of white paper to knock some of them off for closer inspection.

If preventative or control action must be taken, consider biological control methods before using insecticides.

Use Insecticidal Sprays as knockdowns or on large thrips populations that beneficial insects cannot control.

  • Insecticidal Soap applied directly to active thrips will kill on contact, but should not be depended on for full control of the infestation.
  • Neem Oil sprays can be used to knockdown thrips infestations before introducing beneficials. If the population is unaffected by neem oil, then consider using Pyganic, a Pyrethrin-based contact insecticide.
  • Spinosad can also be used to control thrips and provides residual control effects that the products above do not.
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