''Steneotarsonemus spinki'', the panicle rice mite, spinki mite, or rice tarsonemid mite, is a species of

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear e ...

in the family

Tarsonemidae Tarsonemidae is a family of mites, also called thread-footed mites or white mites. Only a limited number of tarsonemid genera ('' Steneotarsonemus'', '' Polyphagotarsonemus'', '' Phytonemus'', '' Floridotarsonemus'' and '' Tarsonemus'') are kno ...

, the white mites. It is a serious pest of

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

, and the Caribbean.

Identification

The panicle rice mite is not visible to the naked eye. A minimum 20×

hand lens A magnifying glass is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle. A magnifying glass can be used to focus light, such as to concentrate the sun's radiation to crea ...

is required to observe it on the inside of the

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

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.

Larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

l stages, as well as eggs are about half the size of adults.

Life history

Panicle rice mites are

parthenogenetic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...

(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 A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physic ...

can vary from 3 days at 86 °F to 20 days at 68 °F. If held in the laboratory at 17.6 °F for 72 hours, all panicle rice mites will die. High temperatures and low rainfall are ideal for development of large populations of panicle rice mites in the

field Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grass ...

. Continuous rice culture and the sharing of equipment between fields is also conducive to building damaging populations of the mites.

Distribution

The mite has been extremely destructive in rice fields of tropical regions of Asia, particularly in China and

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

, 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 The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

in 2007, and has been found in

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the O ...

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

and New York. Until the discovery at

UC Davis The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The institut ...

, it had never been identified in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

or elsewhere in the western United States. On July 13, 2007, the

United States Department of Agriculture The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of com ...

confirmed the presence the panicle rice mite at a rice research facility in

Alvin Alvin may refer to: Places Canada *Alvin, British Columbia United States *Alvin, Colorado *Alvin, Georgia *Alvin, Illinois * Alvin, Michigan *Alvin, Texas * Alvin, Wisconsin, a town *Alvin (community), Wisconsin, an unincorporated community Other ...

Brazoria County, Texas Brazoria County ( ) is a county in the U.S. state of Texas. As of the 2020 census, the population of the county was 372,031. The county seat is Angleton. Brazoria County is included in the Houston-The Woodlands-Sugar Land metropolitan sta ...

. Other interceptions of this pest have also been reported at greenhouses in Ohio and Texas within the last 10 years. In January, 2009, officials at 11 University of California Davis greenhouses discovered panicle rice mite contamination. 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 The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north a ...

climate with both high temperature and high humidity. 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 ''Sarocladium oryzae'' (Sawada) is a plant pathogen causing the sheath rot disease of rice and bamboo blight in Asia. Taxonomy and morphology ''Sarocladium oryzae'' has irregularly penicillate conidiophores and slimy, 1-celled conidia. ''Sa ...

'' ( sheath rot)

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

s. These pathogens are both present in southwest Louisiana.

Host plants

Panicle rice mites are pests of commercial rice (''

Oryza sativa ''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yan ...

''), and completes its development on the invasive plant '' Oryza latifolia''.

Damage

Feeding takes place behind the leaf sheath. The feeding lesion can be detected by cinnamon to

chocolate Chocolate is a food made from roasted and ground cacao seed kernels that is available as a liquid, solid, or paste, either on its own or as a flavoring agent in other foods. Cacao has been consumed in some form since at least the Olmec civ ...

-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 A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

pathogens. During feeding, they inject a

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

saliva. The mites have been associated with sheath rot as well as

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

l 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. Crop losses ranging from 5% - 90% have been attributed to panicle 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%.

Management

Chemical

Chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...

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.

Biological

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

Cultural

Cultural controls include

plowing A plough or plow (Differences between American and British spellings, US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are draw ...

stubble after

harvesting Harvesting is the process of gathering a ripe crop from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper. On smaller farms with minimal mechanization, harvesting is the most labor- ...

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.

References

External links

United States Department of Agriculture
{{Taxonbar, from=Q7607553 Trombidiformes Agricultural pest mites Animals described in 1967 Arachnids of Asia