Rice Beetle | Dyscinetus morator (Fabricius)

California Pest Rating  for
Rice Beetle | Dyscinetus morator (Fabricius)
Coleoptera: Scarabaeidae
Pest Rating: A



Initiating Event:

Dyscinetus morator is currently Q-rated.  A permanent pest rating proposal is required to support an official pest rating.

History & Status:

Background:  Adult Dyscinetus morator are beetles that measure ½ to ¾ of an inch in length.  They are black and shining with a slightly greenish sheen (Woodruff, 1999).  Adults feed on plant material aboveground, underground, and even under water.  They have been reported to feed on, burrow into, and cause significant damage (including crop losses up to 30%) to carrots and radishes in Florida (Foster et al., 1986).  Ornamental plants are also affected.  For example, tubers of caladium were attacked by D. morator adults in Florida (Price and Kring, 1991).   Adults were also reported to feed on leaves of a variety of crop species in the laboratory, including lettuce, peas, squash, and tomato. They apparently thrive in aquatic habitats and can spend several hours submerged under water while feeding on aquatic plants, including the aquatic weed Salvinia minima (Jäch and Balke, 2008; Parys et al., 2013).  Dyscinetus morator larvae are C-shaped, whitish grubs that live underground.  They are reported to feed on roots, including those of azalea (Rhododendron spp.) and juniper (Juniperus sp.) (Price and Kring, 1991; Staines, 1990).  The larvae may also feed on accumulations of decomposing organic matter, including compost (Richter, 1958).

Worldwide Distribution:  Dyscinetus morator is reported from the Caribbean (Bahamas, Cuba, and Puerto Rico) and the eastern United States (from Florida north to New York and west to Texas) (Ratcliffe and Cave, 2008; Staines, 1990).  This species is apparently native to the eastern United States, and the Caribbean records may represent introductions (Ratcliffe and Cave, 2008).

Official Control: Dyscinetus morator is not known to be under official control anywhere.

California Distribution:  Dyscinetus morator is not known to occur in California.

California Interceptions:  Dyscinetus morator has been intercepted on a variety of items, including nursery stock, from Arkansas, Florida, Georgia, Mississippi, Tennessee, Texas, Virginia, and possibly other states.  This beetle was found inside a warehouse in Alameda County in 1999 (CDFA Pest and Damage Report Database, 2018).

The risk Dyscinetus morator would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Dyscinetus morator is widely distributed in the eastern United States and the Caribbean, which suggests it has broad climatic tolerances and could establish over a large portion of California. This beetle is reported to feed on a wide variety of plants, including many crops and ornamentals, and would likely find suitable host plants over a large portion of California.  Therefore, Dyscinetus morator receives a High (3) in this category.

– 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: Dyscinetus morator has been reported to feed on a wide variety of plants in at least eight families. Therefore, it receives a High (3) in this category.

– 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: Dyscinetus morator flies to light in large numbers (Woodruff, 1999).  Larvae of morator have been found in potted juniper plants, so it is possible that this beetle could be artificially dispersed through movement of potted nursery plants (Price and Kring, 1991).  Therefore, it receives a Medium (2) in this category.

– 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: Dyscinetus morator is known to cause significant damage to crop plants in certain situations.  If this beetle became established in California, it could reduce yield and increase production costs of many different crops.  The presence of this species in nurseries could trigger the loss of markets, as the larvae could occur in soil in potted plants.  Therefore, it receives a High (3) in this category.

Economic Impact:  A, B, C

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: Dyscinetus morator is reported to attack crop and ornamental plants. If this species became established in California, it could trigger treatment programs in agricultural settings as well as in ornamental settings, including nurseries and gardens.  This species feeds on a wide variety of plants and can tolerate a wide range of conditions.  This beetle could invade natural California ecosystems and attack native plants. Therefore, it receives a High (3) in this category.

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

Environmental Impact:  A, 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:

Environmental Impact Score: 3

– 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 Dyscinetus morator: High (14)

Add up the total score and include it here.

–Low = 5-8 points

–Medium = 9-12 points

–High = 13-15 points

Post Entry Distribution and Survey Information: Dyscinetus morator is not known to be present in California. It receives a Not established (0) in this category.

–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)


There appears to be little uncertainty regarding the potential for this beetle to become established in California.  Even though this beetle is often very abundant and has been reported to feed on and cause significant damage to a wide variety of crop and ornamental plants in certain situations, its significance as a pest seems to be restricted in time and space.  This could be because this species is native to most of the area that it is known to occur in and is being controlled by natural enemies (predators and parasitoids).  If this species was introduced to California, it may escape the natural enemies present in the eastern United States.

Conclusion and Rating Justification:

Dyscinetus morator is a highly polyphagous plant-feeding beetle that is not known to occur in California.  If it became established in California, it could have severe economic and environmental impacts.  For these reasons, an “A” rating is justified.


CDFA Pest and Damage Report Database. 2018.  Dyscinetus morator. Plant Health and Pest Prevention Services. CA Department of Food and Agriculture. Accessed April 6, 2018: http://phpps.cdfa.ca.gov/user/frmLogon2.asp

Foster, R. E., Smith, J. P., Cherry, R. H., and Hall, D.G.  1986.  Dyscinetus morator (Coleoptera: Scarabaeidae) as a pest of carrots and radishes in Florida 69:431-432.

Jäch, M. A. and Balke, M.  2008.  Global diversity of water beetles (Coleoptera) in freshwater.  Hydrobiologia 595:419-442.

Parys, K. A., Gimmel, M. L., and Johnson, S. J.  2013.  Checklist of insects associated with Salvinia minima Baker in Louisiana, USA.  CheckList 9:1488-1495.

Price, J. F. and Kring, J. B.  1991.  Dyscinetus morator (Coleoptera: Scarabaeidae) flight activity, food plant acceptance, damage and control in caladium.  Florida Entomologist 74:415-421.

Ratcliffe, B. C. and Cave, R. D.  2008.  The Dynastinae (Coleoptera: Scarabaeidae) of the Bahamas with a description of a new species of Cyclocephala from Great Inagua Island.  Papers in Entomology 105:1-10.

Ritcher, P. O.  1958.  Biology of Scarabaeidae.  Annual Review of Entomology 3:311-334.

Staines, C. L.  1990.  Dyscinetus morator (Coleoptera: Scarabaeidae) feeding on roots of azaleas (Rhododendron spp.) 101:98.

Symbiota Collections of Arthropods Network.  Accessed April 6, 2018: http://scan1.acis.ufl.edu

Woodruff, R. E.  1999.  Rice beetle, Dyscinetus morator (Fabricius) (Insecta: Coleoptera: Scarabaeidae).  EENY-102.  Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.


Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741; plant.health[@]cdfa.ca.gov.

Responsible Party:

Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211, plant.health[@]cdfa.ca.gov

Comment Period:* CLOSED

6/25/18 – 8/09/18


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Pest Rating: A


Posted by ls