Radionaspis indica (Marlatt) | Mango Scale | Pest Rating Proposals and Final Ratings

California Pest Rating for

Radionaspis indica (Marlatt): Mango Scale

Hemiptera: Diaspididae

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

Since 2005 Radionaspis indica has been regularly intercepted on mango fruit by CDFA’s border stations and dog teams. This scale insect presently has a temporary rating of “Q”. A pest rating proposal is needed to establish a permanent pest rating.

History & Status:

Background: Radionaspis indica is a monophagous scale insect that feeds on the trunk, branches, and buds of mango trees (Mangifera indica (Anacardiaceae)). Severe infestations can cause cracking of bark, exudation of sap, and decline of branches². Radionaspis indica may rapidly disperse long distances in the trade of infested mango fruit or nursery stock.

Worldwide Distribution: Radionaspis indica may be native to India and is also found in Indonesia, the Federated States of Micronesia, Palau, Cape Verde, Senegal, Cuba, the British Virgin Islands, the Dominican Republic, Jamaica, and Panama³. In the United States the scale is found in Hawaii, Florida, and Puerto Rico³. Regular interceptions of the scale on mangos from Mexico suggest that it is established in that country.

Official Control: Radionaspis indica is not known to be under official control in any states or nations.

California Distribution: Radionaspis indica has never been found in the environment of California.

California Interceptions: Between January 1, 2005 and December 31, 2015 Radionaspis indica was intercepted 69 times on mango fruit by CDFA’s border stations and dog teams. It was also intercepted once on papaya.

The risk Radionaspis indica (mango scale) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Mango trees require warm, dry weather to set fruit. In California the best locations are away from immediate marine influences in the deserts, foothills, and the warmest cove locations of the California Central Valley^{4,5, 6}. Mango trees are also sometimes grown as ornamental plants in urban environments and are present in the nursery industry. Radionaspis indica is expected to be able to establish in all of these environments. It receives a Medium(2) 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: Radionaspis indica only feeds on mango and receives a Low(1) 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: Armored scales have high reproductive potential. Mango fruit is not considered to be a good pathway for dispersal of Radionaspis indica due the limited mobility of female armored scales and crawlers and the species’ limited host range. However, the scales have high dispersal potential because they are able to disperse long distances rapidly on nursery stock and are able to disperse to any nearby trees by crawling, by wind, or by hitchhiking on clothing, equipment, or other animals. Radionaspis indica 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: California growers produce between 250,000 and 4,000,000 pounds of mango annually⁶. This is a high value commodity produced for local sales at specialty markets and demand is increasing⁶. California grown mangos are generally produced organically⁵. If Radionaspis indica were to enter California and become established in groves it could potentially reduce yields of this crop if heavy infestations cause branch dieback². Furthermore, the scale has potential to both lower crop value by disfiguring fruit and nursery stock with its presence and increase production costs by triggering new chemical treatments. Radionaspis indica receives a Medium(2) 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: Radionaspis indica is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. The scale is not expected to feed on any endangered or threatened species or disrupt critical habitats. It is possible that its entry could trigger new treatment programs in orchards and nurseries and by residents who find infested trees unsightly. The scale is not expected significantly impact cultural practices, home/urban gardening, or ornamental plantings. Radionaspis indica receives a Medium(2) 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 Radionaspis indica (mango scale): Medium(10).**

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: Radionaspis indica 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: Medium(10)

Uncertainty:

It is possible that sometimes the presence of Radionaspis indica on fruit is indicative of home-grown mangos that have not been produced under commercial phytosanitary safeguards. Any failure to take action on Radionaspis indica infested fruit may increase the risk of introducing exotic fruit flies and other more damaging pests into California.

Conclusion and Rating Justification:

The impacts of the entry of Radionaspis indica into California are expected to be limited to mango groves, nurseries, and scattered ornamental plantings. Nevertheless, this scale insect may have significant economic and environmental impacts to this growing industry. A “B” rating is justified.

References:

¹Litz, Richard E. 2009. The Mango: Botany, Production, and Uses. CABI. 680pp. http://books.google.com/books?id=oloEhPYqE8QC&dq=Radionaspis+indica&source=gbs_navlinks_s

²Peña, Jorge E. 1994. Update on status of pests of tropical fruit crops in south Florida. Proc. Fla. State Hort. Soc. 107: 340-342. http://fshs.org/proceedings-o/1994-vol-107/340-342%20%28PENA%29.pdf

³ Ben-Dov, Y. (2014) ScaleNet, Radionaspis indica. Accessible online at: http://www.sel.barc.usda.gov/catalogs/diaspidi/Radionaspisindica.htm

⁴Grown in California website. Mango fruit facts page. http://www.grownincalifornia.com/fruit-facts/mango-facts.html

⁵Marks, Michael. 2013. Mango orchards in California? San Jose Mercury News. http://www.mercurynews.com/food-wine/ci_24089949/mango-orchards-california

⁶Karp, David. 2014. Mango madness. Sunset. http://www.sunset.com/travel/california/mango-madness

Responsible Party:

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

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