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Thrips feeding distorts or scars leaves, flowers, or fruit. Healthy woody plants
usually tolerate thrips, although damage may become unattractive. Herbaceous ornamentals and developing fruits
and vegetables can be more seriously injured. Use an integrated program combining good cultural care, pest
exclusion, planting thrips-resistant species, and protecting natural enemies by using least-toxic insecticides.
Thrips are tiny, slender insects with hairs on their wing margins.
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They are less than 1/20 inch long and their color varies,
depending on the species and life stage.
- Thrips hatch from eggs and develop through two feeding larval
(nymphal) stages, two nonfeeding stages (prepupa and pupa), and the adult.
- Certain thrips are beneficial predators of insects and mites.
- Most pest thrips feed hidden, often in buds and shoot tips
or under sepals, and damage is often observed before thrips are seen.
- Greenhouse thrips and western flower thrips are two common
pest species in landscapes.
Damage is often not apparent until tissue grows and expands. Look for:
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Dark to brown, scabby or pale to silvery discoloration on fruit, leaves, or petals.
- Dark specks of excrement on fruit or leaves.
- Distorted, curled, galled, or dead shoot tips and leaves.
Check for thrips before you treat!
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Be certain that pest thrips are present and causing damage before taking control action. Harsh weather, inadequate
plant care, pathogens, and other invertebrates can cause damage resembling that from thrips. Shake foliage
or flowers over white paper to see if any thrips are dislodged. Hang bright yellow sticky traps to detect flying
thrips.
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Thrips are difficult to control. Combine methods in an IPM program:
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Find out what species you have and research the best approach; see Pest Notes Thrips.
- Conserve parasites and predators by avoiding persistent
pesticides.
- Avoid overwatering or applying nitrogen fertilizer,
which may increase thrips populations.
- Prune off declining, injured, or infested plant
parts.
- Apply row covers, or cages over small plants to
exclude thrips.
- Cover soil with reflective mulch, which repels flying
thrips if foliage covers less than about half of the soil surface.
Pesticides won’t restore the appearance of injured tissue. Plants remain damaged until injured tissue
drops or is pruned off and new growth appears. Thrips are hard to control with pesticides. Often pesticides
won’t be effective unless you wait until the next season and spray new growth. Horticultural oils, insecticidal soaps, and pyrethrins may provide temporary control, especially for greenhouse
thrips. Spinosad can be more effective. Pesticides alone rarely provide good control, so combine spraying with
other methods
Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal. |
