Scirtothrips dorsalis Hood: (Chilli Thrips)

California Pest Rating for

Scirtothrips dorsalis Hood: (Chilli Thrips)

Thysanoptera: Thripidae

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

In August 2015 infestations of Scirtothrips dorsalis were found at several residential properties in Orange County. A pest rating proposal is required to determine future direction on this pest.

History & Status:

Background: Scirtothrips dorsalis is a polyphagous thrips that is reported to feed on more than 200 plant species in 70 families³. Known hosts include economically important crops such as roses, chilies, grapes, citrus, avocado, tomato, and strawberry^1,2,3. The thrips has been recorded killing newly emerged seedlings, severely distorting leaves, scarring the surface of fruits, and vectoring major plant pathogens³. The thrips may spread long distances through the trade of plants, fruit, or cut flowers.

Worldwide Distribution: Scirtothrips dorsalis is believed to be native to South-East Asia or the Indian subcontinent⁴. It has spread across much of Asia and to parts of Australia, Papua New Guinea, and the Solomon Islands. It has also been found on several Caribbean islands as well as in Suriname, Venezuela, and Ivory Coast¹. It was detected in Hawaii in 1987, Florida in 2005, Puerto Rico in 2006, Georgia and Texas in 2007, and Louisiana in 2009.

Official Control: Scirtothrips dorsalis is considered a quarantine pest in Europe⁵ and New Zealand⁶.

California Distribution: Scirtothrips dorsalis has only been found in the environment of California in Orange and Los Angeles counties.

California Interceptions: Scirtothrips dorsalis is occasionally intercepted on plants or fresh plant parts from Florida, Texas, and Hawaii.

The risk Scirtothrips dorsalis (Chilli thrips) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: The present distribution of Scirtothrips dorsalis corresponds to USDA plant hardiness zones 8-12, indicating that it is likely to find a favorable climate in most of California. The polyphagous nature of thrips makes it likely that the insect would encounter suitable host plants throughout the state. Chilli thrips 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: Scirtothrips dorsalis is a polyphagous thrips that is reported to feed on more than 200 plant species in 70 families³. Chilli thrips 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: Chilli thrips reproduces rapidly: each female lays 60-200 eggs and the thrips completes its life cycle in 12-22 days². The thrips is reported to disperse only 12-20m on its own¹, but it may spread long distance in commerce on plants or plant parts. Scirtothrips dorsalis 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: Although Scirtothrips dorsalis is not reported to be a significant economic pest in Florida, there could be impacts to fresh navel orange and table grape exports from California. Citrus is a known host of the thrips, and thrips are notorious for hiding inside the navel of oranges and eluding packing house cleaning. As chilli thrips is considered to be a quarantine pest by New Zealand and Europe, the presence of this insect in California may trigger a loss of markets. Chilli thrips also feeds on a wide variety of ornamental plants, which it disfigures by causing leaf curling. This may increase production costs or lower the value of nursery stock. Chilli thrips has been reported to vector seven major plant pathogens: chilli leaf curl virus, peanut necrosis virus, melon yellow spot virus, watermelon silver mottle virus, capsicum chlorosis virus, and tomato spotted wilt virus⁴. Scirtothrips dorsalis receives a High (3) in this category.

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

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.

– 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: Munz’s onion (Allium munzii), Yosemite onion (Allium yosemitense), and small-leaved rose (Rosa minutifolia) are listed as threatened or endangered plants in California and are potential hosts of Scirtothrips dorsalis. The thrips is likely to trigger additional treatment programs by residents who find infested plants unsightly, as well as by the nursery industry. Chilli thrips receives a High (3) in this category.

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

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 Scirtothrips dorsalis (Chilli 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: Scirtothrips dorsalis has been confirmed in Orange and Los Angeles Counties and receives a Low (-1) 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 (14)

Uncertainty:

There have not been any statewide thrips surveys in recent years; it is possible that Scirtothrips dorsalis could have a more widespread distribution in California. There are no effective detection technologies that would allow for a survey to delimit the infestation or find new infestations in other areas. Because the thrips lays eggs inside plant tissue and is polyphagous, visual surveys might not find low levels of infestation in nurseries or the environment. It is also possible that existing treatments for thrips may also limit impacts of chilli thrips.

Conclusion and Rating Justification:

The spread of Scirtothrips dorsalis through California is likely to have significant economic and environmental impacts. However, it is already known to be established in Orange and Los Angeles Counties and is not under official control. Scirtothrips dorsalis is already established in other states, has been proposed for deregulation by USDA, and is not known to be under consideration for FRSMP. A “B” rating is justified.

References:

¹Culliney, T.W. 2014. Deregulation Evaluation of Established Pests (DEEP); DEEP Report on Scirtothrips dorsalis Hood: Chilli thrips.

² Ludwig, Scott W. and C. Bográn. 2007. Chilli Thrips: A New Pest in the Home Landscape. Texas Cooperative Extension. https://insects.tamu.edu/extension/publications/epubs/eee-00041.pdf

³Kumar, Vivek, Dakshina R. Seal, Garima Kakkar, Cindy L. McKenzie, and Lance S. Osborne. 2012. New tropical fruit hosts of Scirtothrips dorsalis (Thysanoptera: Thripidae) and its relative abundance on them in south Florida. Florida Entomologist 95(1):205-207. http://www.bioone.org/doi/pdf/10.1653/024.095.0134

⁴High Priority Organism: Scirtothrips dorsalis (Chilli thrips). New Zealand Kiwifruit Vine Health Inc. http://www.kvh.org.nz/vdb/document/91534

⁵EPPO Data Sheets on Quarantine Pests: Scirtothrips dorsalis. https://www.eppo.int/QUARANTINE/insects/Scirtothrips_dorsalis/SCITDO_ds.pdf

⁶New Zealand Import Risk Analysis: Table Grapes (Vitis vinifera) from China. 2009. MAF Biosecurity New Zealand. http://www.biosecurity.govt.nz/files/regs/imports/risk/table-grapes-china-ra.pdf

Responsible Party:

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

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