California Pest Rating
Acutaspis agavis (Townsend & Cockerell): Agave scale
Current Pest Rating: Q
Proposed Pest Rating: B
FINAL Pest Rating: B
On March 21, 2014, Dr. Gillian Watson identified the armored scale Acutaspis agavis from a sample collected from plants growing outdoors at a school in La Jolla, San Diego County. A heavy infestation was reported at the site on the adaxial leaf surfaces of Agave tequilana. Tissue dieback was reported on the most infested leaves and there was no evidence of parasitism or predation. The insect is currently Q-rated, so a pest rating proposal is needed to determine future direction.
History & Status:
Background: Acutaspis agavis is host specific to Agave spp. The primary pathway for spread of the scale is likely the movement of infested agave plants.
Worldwide Distribution: Acutaspis agavis is probably native to Mexico. It has also been reported from Costa Rica, Venezuela, and Trinidad and Tobago. In the United States it has been found in Arizona, Florida, and Texas.
Official Control: Acutaspis agavis is not known to be under official control in any other states or nations.
California Distribution: Acutaspis agavis is only known from an incursion at a school in La Jolla.
California Interceptions: The only instance of an Acutaspis agavis detection in a regulatory situation was in a nursery in El Cajon in 2012.
The risk Acutaspis agavis (Agave scale) would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: Agave are commonly grown as ornamental plants in California and the scale is expected to be able to establish wherever they are grown. Acutaspis agavis 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: Acutaspis agavis is specific to Agave The scale 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: Evidence suggests that Acutaspis agavis has two generations per year2 and each female is presumably capable of laying hundreds of eggs. Adult female armored scales are immobile, but populations may be transported long distances through commerce in infested plants. Acutaspis agavis 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: Acutaspis agavis has the potential to increase production costs of Agave plants in the nursery industry. The scale is not expected to lower crop yield, trigger lost markets, alter cultural practices, vector other organisms, injure animals, or interfere with water supplies. Agave scale receives a Low(1) 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: Acutaspis agavis has the potential to trigger new chemical treatments in the nursery industry and by residents who find infested plants unsightly. Agave plants are popular and widely grown, especially in southern California. In the absence of natural enemies agave scale has the potential to significantly impact these cultural practices. Agave scale is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. The scale is also not expected to affect threatened or endangered species or disrupt critical habitats. Agave scale 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 Acutaspis agavis (Agave scale): Medium(11)
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: Acutaspis agavis is only known from an incursion at a school in La Jolla. It is unknown if the scale has spread to other agave plants in the area. Agave scale 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.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium(10)
Agave plants are popular landscape plants, especially in southern California. There have been no surveys for Acutaspis agavis and it may be present in other locations.
Conclusion and Rating Justification:
Economic impacts of Acutaspis agavis should be limited to possible increases in production costs of agave plants in the nursery industry. However, the entry of agave scale into California may have significant environmental impacts due to the popularity of the plant and the absence of its natural enemies. A B-rating is justified.
1Systematic Entomology Laboratory. http://www.sel.barc.usda.gov/catalogs/diaspidi/Acutaspisagavis.htm
2Salas-Araiza, M.D., R.W. Jones, G. Montesinos-Silva, E. Salazar-Solis, L.A. Parra-Negrete, O. Martinez-Jaime, R. Ramirez-Malagon, and S. Flores-Mejia. 2008. Population dynamics of the agave scale, Acutaspis agavis (Hemiptera: Diaspididae), on Agave tequilana var. azul (Agavaceae) in Central Mexico. Southwestern Entomologist 33(4):289-298. http://www.bioone.org/doi/abs/10.3958/0147-1724-33.4.289
Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211, plant.health[@]cdfa.ca.gov.
The 45-day comment period opened on Wednesday, October 21, 2015 and closed on December 5, 2015.