Panicle rice mite

Steneotarsonemus spinki
Adults and eggs
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Subclass: Acari
Order: Trombidiformes
Family: Tarsonemidae
Genus: Steneotarsonemus
Species: S. steneotarsonemus
Binomial name
Steneotarsonemus spinki
Smiley, 1967

Steneotarsonemus spinki, also known as Panicle rice mite,[1] spinki mite and rice tarsonemid mite,[2] is a serious rice pest in several Asian tropical regions, Central America and the Caribbean.


The panicle rice mite is not visible to the naked eye. A minimum 20× hand lens is required to observe it on the inside of the leaf sheath. The mites are clear to straw-colored and are approximately 250 µm in length. The male has elongated rear legs containing a pair of elongated spines. The legs are carried above the body. Males are highly active and can be seen moving on the surface of the leaf. Females are ovoid-shaped. Larval stages, as well as eggs are about half the size of adults.

Life history

Parnicle rice mites are parthenogenetic (virgin females can produce male offspring). The female will then mate with the male offspring and produce eggs. A mated female produces an average of 55 eggs in her lifetime. The lifecycle in the laboratory can vary from 3 days at 86 ºF to 20 days at 68 ºF. If held in the laboratory at 17.6 ºF for 72 hours, all parnicle rice mites will die.

High temperatures and low rainfall are ideal for development of large populations of parnicle rice mites in the field. Continuous rice culture and the sharing of equipment between fields is also conducive to building damaging populations of the mites.


The mite has been extremely destructive in rice fields of tropical regions of Asia, particularly in China and Taiwan, and in and Central America. The mite has wiped out commercial rice fields in the Caribbean region.

The panicle rice mite was first introduced into the United States in 2007, and has been found in Louisiana, Arkansas, Texas, Ohio and New York.[3] Until the discovery at UC Davis, it had never been identified in California or elsewhere in the western United States. On July 13, 2007, the United States Department of Agriculture confirmed the presence the panicle rice mite at a rice research facility in Alvin, Brazoria County, Texas. Other interceptions of this pest have also been reported at greenhouses in Ohio and Texas within the last 10 years.[4]

In January, 2009, officials at 11 University of California Davis greenhouses discovered panicle rice mite contamination.[5] Although panicle rice mites are not thought to have the ability to thrive in the temperate climate of the United States, the area of southwest Louisiana has a sub-tropical climate with both high temperature and high humidity.[6]

Panicle rice mites thrive under both of these conditions and may cause substantial economic losses when found in association with Burkholderia glumae (bacterial panicle blight) and Sarocladium oryzae (sheath rot) pathogens. These pathogens are both present in southwest Louisiana.

Host plants

Panicle rice mites are pests of commercial rice (Oryza sativa), and completes its development on the invasive plant Oryza latifolia.


Feeding takes place behind the leaf sheath. The feeding lesion can be detected by cinnamon to chocolate-brown discoloration of the leaf sheath. When a new leaf begins development, a female will move to the new leaf sheath, produce male offspring and then establish a new feeding lesion. Thus, damage will often be observed on interior sheaths when the outer sheath is removed. This continues until the mite reaches the leaf nearest the stem. They also feed on developing panicles from the boot stage to the milk stage of heading.

Panicle rice mites cause damage to plants by directly feeding on leaf tissue in the leaf sheath and developing grains at the milk stage, and indirectly, by transmitting fungal pathogens. During feeding, they inject a toxic saliva. The mites have been associated with sheath rot as well as bacterial panicle blight. The mites can carry sheath rot spores on their body.

The mites cause damage to plant tissue which may facilitate entry of fungal pathogens into developing grains and the leaf sheath. This damage to grains results in sterility and deformed grains, straight-head, and parrot-beaking of grains.[5]

Crop losses ranging from 5% - 90% have been attributed to parnicle rice mites in a number of countries.

In the Americas, however, it has caused the largest economic impact. In Central America it has caused yield losses ranging from 30% to 90%.



Chemical controls are usually not efficacious because the mites remain present in a water-sealed area of the plant -- behind the leaf sheath and near the stem. Thus, systemic miticides may be the best option for chemical control.


Fungal pathogens and predatory mites may have the ability to suppress populations.


Cultural controls include plowing stubble after harvesting crops, as well as ensuring no re-growth of plant material for winter, fallowing fields, rotation with an alternate crop, cleaning machinery before use in an un-infested field, sampling two weeks after planting to catch mite populations at low levels, and avoidance of second-cropping.

These cultural control methods as well as breeding for resistance have successfully suppressed populations in some infested countries.


Further reading

  • Pest management in rice in tropical Asia
  • Ho, C.C. and K.C. Lo. 1979. A survey of the host ranges of Steneotarsonemus spinki (Acari: Tarsonemidae). National science Council Monthly. 7(10): 1022-1028. [Article in Chinese; Abstract in English].
  • Jiang, P.Z. et al. 1994. Regularity of incidence of Steneotarsonemus spinki and its control. Guangdong Agricultural Sciences. 5: 37-40. [Article in Chinese; Abstract in English].
  • Lo, K.C. and C.C. Ho. 1980. The rice tarsonemid mite Steneotarsonemus spinki. Plant Protection Bulletin Taichung. 22(1): 1-10. [Article in Chinese; Abstract in English].
  • Lo, K.C. et al. 1979. Artificial propagation of Amblyseius taiwanicus Ehara and its tolerance of some pesticides. Journal of Agricultural Research China. 28(4): 251-259. [Article in Chinese; Abstract in English].
  • Lo, K.C. et al. 1981. Screening of chemicals for the control of rice tarsonemid mite, Steneotarsonemus spinki. Journal of Agricultural Research China. 30(3): 303-307. [Article in Chinese; Abstract in English].
  • Ochoa, R. 2004a. E-mail from Dr. Ronald Ochoa to Mr. Keith Colpetzer dated 12 March 2004. Subject: telephone conversation 3-12-2004. On file with USDA, APHIS, PPQ.
  • Ochoa, R. 2004b. E-mail from Dr. Ronald Ochoa to Dr. Robert (Bob) Carlson dated 2 February 2004. Subject: Steneotarsonemus spinki (Acari: Tarsonemidae) New to Ohio and USA. On file with USDA, APHIS, PPQ.
  • PIN309, 2004. Port Information Network: Pest Interceptions (309) Application. USDA, APHIS, PPQ. (Queried 18 March 2004).
  • Ramos, M. and H. Rodríguez. 2001. Aspectos biológicos y ecológicos de Steneotarsonemus spinki en arroz, en Cuba. Manejo Integrado de Plagas. 61: 48-52.
  • Ramos, M. et al. 2001. Presencia de Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) en cuatro variedades de arroz en le Republica Dominicana. Revista de Proteccion Vegetal. 16(1): 6-9.
  • Rao, J. and A. Prakash. 2002. Paddy field weed, Schoenoplectus articulatus (Linn.) Palla (Cyperaceae): A new host of tarsonemid mite, Steneotarsonemus spinki Smiley, and panicle thrips, Haplothrips ganglbaureri Schmutz. Journal of Applied Zoological Research. 13(2/3): 174-175.
  • Rao, P.R.M. et al. 2000. Spikelet sterility/grain discoloration in rice in Andhra Pradesh, India. International Rice Research Notes. 25(3): 40.

External links

  • United States Department of Agriculture