Tag Archives: Japanese flower thrips

Japanese Flower Thrips | Thrips setosus

California Pest Rating for
Thrips setosus Moulton: Japanese flower thrips
Photo Citation: Mound, L. (2005), PaDIL – http://www.padil.gov.au
Thrips setosus Moulton: Japanese flower thrips
Thysanoptera: Thripidae
Pest Rating:  A


Initiating Event:

USDA is considering changing the status of Thrips setosus from actionable to non-actionable.  A pest rating proposal is needed to advise direction on this insect.

History & Status:

Background:  Thrips setosus is a polyphagous leaf and flower-feeding thrips.  Female thrips lay eggs in leaves where they are difficult to detect and protected from chemical treatment.  Nymphs and adults feed on plants and cause silvering or bronzing of leaves and leaf scorching.  Known hosts include:  Apiaceae: hogweed (Heracleum sphondylium1); Asparagaceae: Hosta sp.1; Asteraceae: Chrysanthemum morifolium1, Erigeron sp.1, sowthistle (Sonchus oleraceus1), oriental false hawksbeard (Youngia japonica1); Balsaminaceae: Impatiens sp.1; Cucurbitaceae: cucumber (Cucumis sativus1); Euphorbiaceae: poinsettia (Euphorbia pulcherrima1); Fabaceae: soybean (Glycine max1), bean (Phaseolus vulgaris1), fava bean (Vicia faba1), asparagus bean (Vigna sesquipedaris1); Hydrangeaceae: Hydrangea sp.1; Lamiaceae: red dead-nettle (Lamium purpureum1); Pedaliaceae: sesame (Sesamum indicum1); Plantaginaceae: foxglove (Digitalis sp.1); Ranunculaceae: Helleborus sp.1; Solanaceae: bell pepper (Capsicum annum1), jimsonweed (Datura stromium1), tomato (Lycopersicum esculentum1), tobacco (Nicotiana tabacum1), Petunia x hybrid1, Carolina horsenettle (Solanum carolinense1), eggplant (Solanum melongena1); and Urticaceae: stinging nettle (Urtica dioica1). Thrips setosus has been associated with many additional plants but host records need confirmation (see uncertainty section).  Thrips setosus can be transported long distances when infested plants, cut flowers, or other fresh plant parts are moved.

Worldwide Distribution: Thrips setosus is presumably native to Japan.  From there, it has spread to Indonesia, The Republic of Korea, Croatia, France, Germany, the Netherlands, and the United Kingdom1.  In the United States, it was first found in 2016 in Michigan in a greenhouse at a nursery that imports plants from multiple nations1.  In that greenhouse, Thrips setosus was able to build up significant populations, despite existing pest management practices.  Since then, the thrips has also been found in the environment surrounding that greenhouse, in associated nursery fields located 11 miles away, and in a trace-forward survey at a greenhouse in Rhode Island1.  The thrips continues to be found in the original infested greenhouse even after multiple treatments.  Before detection, plants from that greenhouse were shipped to 39 other states, so the thrips might be more widespread.  However, trace forward surveys have not found it anywhere else.

Official Control: Thrips setosus is not known to be under official control in any other states or nations.

California Distribution:  Thrips setosus has never been found in the environment in California.

California Interceptions Thrips setosus has never been intercepted by CDFA.

The risk Thrips setosus (Japanese flower thrips) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Thrips setosus is polyphagous and is expected to be able to establish throughout plant hardiness zones 4 to 111. It can be expected to establish throughout almost all of California and receives a High (3) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score:

Low (1) Not likely to establish in California; or likely to establish in very limited areas.

Medium (2) may be able to establish in a larger but limited part of California.

High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Thrips setosus is known to feed on plants in at least 26 genera in 14 plant families.  There are unverified host records on many other plants in 13 additional families.  Thrips setosus receives a High (3) in this category.

Evaluate the host range of the pest. Score:

Low (1) has a very limited host range.

Medium (2) has a moderate host range.

High (3) has a wide host range.

3) Pest Dispersal Potential: Thrips setosus females can lay up to 8 eggs per day and the species can complete 7-12 generations per year, depending on temperature1.  This indicates a high reproductive rate.  Thrips can be transported long distances when infested plants, cut flowers, or other fresh plant parts are moved.  Thrips setosus receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

Low (1) does not have high reproductive or dispersal potential.

Medium (2) has either high reproductive or dispersal potential.

High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Thrips setosus has been documented as a vector of Tomato spotted wilt tospovirus (TSWV)1.  This virus can cause bronzing, curling, necrotic streaks, or spots on tomato leaves, dark-brown streaks on leaf petioles, stems, and growing tips, and infected plants can be stunted1.  In addition, tomato fruit infected with TSWV is discolored1Thrips setosus is considered to be a less efficient vector of TSWV compared to thrips that are already present in California1.  However, in Michigan the thrips has not been controlled by existing thrips management programs and has not been affected by existing biological control agents.  New chemical treatments required for this thrips are likely to disrupt existing IPM programs in California agroecosystems.  Thrips setosus has not been found in other major tomato growing regions and larger populations of a thrips that is more difficult to control are expected to increase spread of the virus.  If the thrips were to establish in California it is likely to lower crop yields, especially for tomatoes.  It is certain to increase crop production costs.  It is also likely to disrupt California exports.  Thrips setosus receives a High (3) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

Economic Impact: A, B, E

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

Low (1) causes 0 or 1 of these impacts.

Medium (2) causes 2 of these impacts.

High (3) causes 3 or more of these impacts.

5) Environmental Impact: If Thrips setosus were to establish in California it is not likely to lower biodiversity, disrupt natural communities, or change ecosystem processes. Several endangered species are closely related to possible hosts (see uncertainty section) and might be directly affected by the thrips including Ashland thistle (Cirsium ciliolatum), fountain thistle (Cirsium fontinale fontinale), Chorro Creek bog thistle (Cirsium fontinale var. obispoense), Suisun thistle (Cirsium hydrophilum var. hydrophilum), La Graciosa thistle (Cirsium loncholepis), surf thistle (Cirsium rhothophilum), Parish’s daisy (Erigeron parishii), Scott’s Valley polygonum (Polygonum hickmanii), showy Indian clover (Trifolium amoenum), Pacific grove clover (Trifolium polyodon), and Monterey clover (Trifolium trichocalyx).  Thrips setosus would not be expected to disrupt critical habitats.  It is likely to trigger new treatment programs by growers, in the nursery industry, and by residents.  Many of the host plants are popular in home/urban gardens and as ornamentals and would likely be significantly impacted by this thrips.  Thrips setosus receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: B, D, E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

Low (1) causes none of the above to occur.

Medium (2) causes one of the above to occur.

High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Thrips setosus (Japanese flower thrips): High (15)

Add up the total score and include it here.

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: Thrips setosus has never been found in California and receives a Not established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Not established (0) Pest never detected in California, or known only from incursions.

Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (15)


In addition to the known hosts described above there many other host records in the literature that have not yet been verified by USDA.  These candidate hosts include:  Amaryllidaceae: amaryllis (Hippeastrum sp.1); Asparagaceae: monkey grass (Liriope platyphylla1), mondo grass (Ophiopogon jaburan1); Asteraceae: pyrethrum (Chrysanthemum cinerariafolium1), Japanese thistle (Cirsium japonicum1), Dahlia sp.1, double Japanese aster (Kalimeris pinnatifida1), Japanese aster (Kalimeris yomena1), lettuce (Lactuca sativa1), Tagetes sp.1; Balsaminaceae: touch-me-not (Impatiens balsamina1); Brassicaceae: cabbage, broccoli, kale, brussels sprouts, collard greens, savoy, kohirabi, and gai lan (Brassica olearacea1); Caprifoliaceae: Abelia spathulata1, Cucurbitaceae: melon (Citrullus battich1), melon (Cucumis melo1), squash (Cucurbita maxima1), squash (Cucurbita moschata1), bitter melon (Momordica charantia1); Dioscoreaceae: Japanese mountain yam (Dioscorea japonica1); Ebenaceae: persimmon (Diospyros kaki1); Fabaceae: Dumasia truncata1, pea (Pisum sativum1), kudzu (Pueraria lobata1), white clover (Trifolium repens1), clover (Trifolium sp.1), vetch (Vicia sativa1); Iridaceae: Iris sp.1; Lamiaceae: henbit (Lamium amplexicaule1), wild mint (Mentha arvensis1), Moraceae: fig (Ficus carica1); Onagraceae: evening primrose (Oenothera sp.1); Poaceae: rice (Oryza sativa1); Polygonaceae: knotweed (Polygonum sp.1); Rosaceae: strawberry (Fragaria ananassa1); Rutaceae: Citrus sp.1; Simaroubaceae: tree of heaven (Ailanthus altissima1); Solanaceae: potato (Solanum tuberosum1); Vitaceae: grapevine (Vitis vinifera1); and Unknown: glory lily1.

Conclusion and Rating Justification:

Thrips setosus has only been found in greenhouses in Michigan and Rhode Island as well as several fields in Michigan associated with the infested greenhouse1.  There is uncertainty about whether or not Thrips setosus can survive in the northern United States1.  Since both Michigan and Rhode Island are northern states and the thrips has not been found elsewhere, it is not yet clear that this species has established in the United States or if it is only a regulatory incident that could be addressed.  If Thrips setosus were to establish in California it is likely to have significant impacts to crops worth as much as $14 billion annually including tomatoes, bell pepper, grapes, citrus, lettuce, melons, rice, strawberry, fig, and Brassicaceae.  The thrips would also be expected to have significant environmental impacts.  An “A” rating is justified.


1 Morrice, Jarrod. 2017.  NPAG Report: Thrips setosus Moulton: Japanese flower thrips. Thysanoptera: Thripidae.  United States Department of Agriculture: Animal and Plant Health Inspection Service: Plant Protection and Quantine.  New Pest Advisory Group. Raleigh, NC.

Responsible Party:

Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211, plant.health[@]cdfa.ca.gov.

Comment Period: CLOSED

7/21/2017 – 9/4/2017


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Pest Rating:  A

Posted by ls