''Orseolia oryzae'', also called the Asian rice gall midge, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of small fly in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Cecidomyiidae Cecidomyiidae is a family of flies known as gall midges or gall gnats. As the name implies, the larvae of most gall midges feed within plant tissue, creating abnormal plant growths called galls. Cecidomyiidae are very fragile small insects us ...

. It is a major

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...

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 ...

. The damage to the crop is done by the larvae which form galls commonly known as "silver shoots" or "onion shoots". The rice plant is stunted and the seed heads fail to develop.

History

In 1890, an unidentified insect was found to be attacking the rice crop in

Munger district Munger district is one of the thirty-eight districts of Bihar state in eastern India. Munger city is the administrative headquarters of this district. Munger district is a part of Munger Division. Its literacy rate of 73.3% is higher than the st ...

Bihar Bihar (; ) is a state in eastern India. It is the 2nd largest state by population in 2019, 12th largest by area of , and 14th largest by GDP in 2021. Bihar borders Uttar Pradesh to its west, Nepal to the north, the northern part of West ...

, in India. The English zoologist

James Wood-Mason James Wood-Mason (December 1846 – 6 May 1893) was an English zoologist. He was the director of the Indian Museum at Calcutta, after John Anderson. He collected marine animals and lepidoptera, but is best known for his work on two other gro ...

identified the insect as a midge, called it ''Cecidomyia oryzae'', and wrote about it in the ''

American Naturalist ''The American Naturalist'' is the monthly peer-reviewed scientific journal of the American Society of Naturalists, whose purpose is "to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance t ...

'', but did not formally describe it. The original outbreak faded away, but another occurred in Mysore in 1901, and others followed. By 1922, the rice crop in Tonkin Province in northern Vietnam was devastated and in 1936, crops in Indonesia were being attacked. It was the Indian entomologist M.S. Mani who in 1934 formally described the insect, retaining the name given it by Wood-Mason, because this was already widely known. In 1941 the midge was reported to be damaging crops in China and in 1946, it was reported from Sudan. In 1951, the Chinese researchers Li and Chiu worked out its life history. Even so, until the next decade it was a minor pest. Suddenly with the

Green Revolution The Green Revolution, also known as the Third Agricultural Revolution, was a period of technology transfer initiatives that saw greatly increased crop yields and agricultural production. These changes in agriculture began in developed countrie ...

came higher yielding but more susceptible varieties, and ever since then ''O. oryzae'' has been among the top four insect pests (overall, not just in rice) in South and

Southeast The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...

Asia and China.

Description

The Asian rice gall midge is a fly about the size of a

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...

. The females are about long, bright red, with broad abdomens and dense short hair, while the males are slightly smaller, yellowish-brown and more slender. ''O. oryzae'' and '' O. oryzivora'' are morphologically, and even microscopically, indistinguishable, and so DNA differentiation methods have been developed.

Distribution

It is a major insect pest of rice in Southern and

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...

. The pest is

distributed Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...

in various regions of

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

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 ...

, and other neighboring countries and farmers face many problems due to the monetary loss caused by this insect pest. It is also found in rice-growing regions of Africa.

Life cycle

The adults are mainly nocturnal and hide during the day. The females lay small batches of eggs (two to six) on the undersides of rice leaves, totalling 100-400 in a lifespan. The eggs are red at first, but by the time they hatch, two to four days later, they are chocolate-brown. The tiny

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. ...

e crawl down the leaf sheath till they reach the leaf axil where they bore their way into the stem. After feeding for about ten days and forming a gall, they

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

te inside. Four to seven days later they use spines on the tip of the abdomen to make a hole in the gall near its tip. Here the adult insects emerge. They live for three or four days, and there may be as many as eight generations of midge in the year.

Hosts

''Oryza sativa'', ''

Cynodon dactylon ''Cynodon dactylon'', commonly known as Bermuda grass, is a grass found worldwide. It is native to Europe, Africa, Australia and much of Asia. It has been introduced to the Americas. Although it is not native to Bermuda, it is an abundant invasiv ...

'', and '' Isachne aristatum''. Scientific investigation of ''O. sativa'' resistance against ''O. oryzae'' began in India in 1948, and ''O. oryzae'' virulence against these ''O. sativa'' cultivars was first observed in 1969.

Damage

The larvae of the Asian rice gall midge irritate the tissues of the rice plant which forms a gall commonly known as a "silver shoot" or "onion shoot". This is a pale cylindrical, hollow tube with a green tip replacing the normal culm (stem). The gall is formed from the walls of the leaf sheath growing together, after which the culm stops developing. The stem is stunted and the seed-head does not develop. When the adult insects emerge, the gall withers away and the shoot dies. The plant may respond by producing more tillers, but these usually become infected in their turn. The disease may be localised and patchy or widespread throughout the crop.