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How to identify it
- Adults are brown to dark brown and tiny: females are about 1.1 to 1.3 mm long, and males are smaller (0.8 to 1.0 mm) and paler, sometimes with a darker head.[1]
- The head is small, narrower than the first thoracic segment behind it, and the wings are brown.[1]
- Under magnification, the antennae have seven segments with the third (and sometimes the fourth) pale, the hind thighs and all the feet are usually pale, and the back edges of the abdominal segments carry rows of small triangular teeth.[1]
- All life stages are found in the flower heads of daisy-family plants.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Onion thrips and other Thrips species | The composite thrips resembles members of the genus Thrips. One of its key features is the small head, narrower than the first thoracic segment.[1] |
Where it lives
Found around the world, mainly in the tropics and subtropics. In the United States it has been reported from Arkansas, California, Colorado, Florida, Georgia, Illinois, Louisiana, Maryland, Oklahoma, South Carolina, Texas, Virginia, Washington and Hawaii. In Florida lettuce fields it was the most common thrips caught in yellow pan traps on commercial farms.[1][2]
Biology and life cycle
The life cycle takes only 9 to 12 days. Females lay eggs in the green bracts under the flower head, timed to when the disk florets are about to open, and the larvae hatch as the flowers open and make nectar.[1]
Larvae and adults pick up pollen on their bodies; a larva can carry several hundred to about a thousand pollen grains, so the species is considered an important pollinator of daisy-family plants.[1][2]
Hosts include sunflower, cosmos, chrysanthemums, calendula, dahlia, marigold, zinnia and daisy-family weeds such as black-jack (Bidens pilosa) and tridax daisy. It also shows up on plants in other families because it visits flowers, including native orchids and citrus in Florida.[1]
When numbers get high, the thrips move from composite flowers onto weeds and vegetable crops.[1]
Damage and signs
- Heavy infestations in daisy-family flowers damage the petals and the base of the flower head: petals lose their color and seed development suffers.[1]
- In south Florida it attacks Indian pole bean grown from May to August. In high numbers its feeding bronzes the leaves, and larvae feeding on the pods can make them unmarketable.[1]
- It carries tobacco streak virus, recorded in parthenium weed, ageratum and tobacco. That virus has been in Florida beans since 1994 and is a growing problem in southern Florida, so researchers recommend watching this thrips closely there.[1][2]
- Damage reports are infrequent overall, and it can live on many ornamental plants without causing obvious harm.[1]
Health risk
UF/IFAS describes it as a pollinator, an occasional plant pest and a plant-virus carrier; it mentions no harm to people.[1]
Control
Prevention
Most of the time no control is needed, since it often causes no obvious damage and helps pollinate daisy-family flowers. Where it is a problem, start management early, while numbers are still low.[1]
Biological control
Minute pirate bugs (Orius species) prey on it and can suppress it well when infestations are low. Avoid broad-spectrum insecticides so these predators can build up.[1]
Pesticides
Insecticidal oil or insecticidal soap can be used early in an infestation.[1]
Common questions
- What are the tiny brown insects in my zinnias and sunflowers?
- They may be composite thrips, which breed in the flowers of daisy-family plants such as zinnias, sunflowers, marigolds and dahlias. Damage from them is reported only infrequently, and they help pollinate the flowers.[1]
- Do composite thrips damage flowers?
- Only in heavy infestations, when petals lose their color and seed set is reduced. Many ornamentals carry them without obvious damage.[1]
- Can composite thrips spread plant viruses?
- Yes. They are a known vector of tobacco streak virus, which also spreads by pollen and seed.[1][2]
Sources
- University of Florida IFAS Extension (EDIS), “Composite Thrips, Microcephalothrips abdominalis (Crawford, 1910), Featured Creatures EENY-712 (R. A. Khan and D. R. Seal, 2018).” journals.flvc.org/edis/article/view/107231 (accessed 2026-11-09)
- Insects (MDPI), “Assessing Abundance and Species Composition of Thrips in Florida Lettuce Fields and Optimizing Monitoring Methods (Williams et al. 2026, Insects 17:676).” pmc.ncbi.nlm.nih.gov/articles/PMC13412098/ (accessed 2026-11-09)
- iNaturalist, “Microcephalothrips abdominalis taxon page (order and family).” www.inaturalist.org/taxa/307946 (accessed 2026-11-09)