INTRODUCTIONBarnyardgrass [Echinochloa crus-gala (L.) Beauv. #3 ECHCG], originally from Europe and India, now ranges from latitude 50 N to 40 S, in both temperate and tropical habitats (12). It is a serious weed problem in 42 countries and is found in at least 27 more (11). It is the world's principal weed of rice(12) and likely has been for a long time: barnyardgrass is recognizable in Chinese drawings from 1590 (13).
The success of barnyardgrass is attributed to prolific seeding, seed dormancy, ability to grow rapidly and flower in a range of photoperiods, and relative resistance to herbicides (15). A healthy full-season barnyardgrass plant in California's Central Valley can produce 750 000 to one million seeds, and as many as 2.25 x 106 seeds under optimal conditions (personal communication, R. F. Norris, Dep. Bot., Univ. Calif., Davis, CA 95616). Moreover, barnyardgrass spread rapidly after the introduction of broadleaf-selective phenoxy herbicides around 1950 (12). Barnyardgrass can grow and flower in photoperiods ranging from 8 to 16 h but prefers the latter. Late summer flushes can still produce seed, because the plant sacrifices vegetative growth for quick flowering (12). However, barnyardgrass is susceptible to shading (15) and is not a serious problem when it emerges after establishment of a tall, vigorous crop. Depending on photoperiod, seed dormancy ranges from 0 to 48 mo. Seed is reported as 100% viable after 6 to 8 yr dry storage (15); seed longevity in soil is of course variable, but in one study it was found that all seeds were nonviable after 15 yr in irrigated sandy loam soil (6).
Barnyardgrass prefers rich, wet soils and low to medium altitudes, but will make do elsewhere (12). E. crus-gala includes several described morphologic varieties as well as varieties which seed in early, mid, and late summer (17). Its close relative junglerice [Echinochloa colonum (L.) Link # ECHCO] infests yet another 27 countries, particularly those with tropical and subtropical climates (11).
Carolus Linnaeus (1707-1778) named barnyardgrass Panicum crus-galli in volume 56 of his Species Plantarum in 1753. Panicum, a genus in which he placed many grasses, is a word meaning `millet' in Latin, and is related to panis, Latin for bread (22). English common names such as panic-grass (19) or chicken panic-grass (12) reflect this etymology rather than the reaction of farmers - or chickens - who discover Echinochloa in their fields. Crus is Latin for leg or shank (22); galli is the possessive form of gallus, Latin for a cock (20). Like some of the plant's later English common names, the specific name likely refers to cockspurs (22). Linnaeus probably saw a cockspur resemblance in the awns of the seed (19).
Ambroise Marie Francois Joseph Palisot de Beauvois (1752-1820) placed barnyardgrass in a new genus, possibly in response to the enormous number of Panicum species. Echinochloa is also a composite word. Echinos, from both Latin and Greek (20), means `prickly' or `spiny.' (The word is also ancestral to the name of the animal phylum of echinoderms, or `spiny skins.') Chloa is Greek for grass or young herbage (22). In 1859, William Darlington suggested a motive for splitting up the genus Panicum: "This vast genus... contain[s] upwards of 400 species... Those here described are inserted merely as samples of a numerous and somewhat variant family" (5). Though the genus Echinochloa was not universally accepted at first, Brewer, Watson, and Gray recognized Echinochloa crus-galli as a synonym for Panicum crus-galli in 1876 (4).A great many varietal differences [at least four recognized varieties in Japan and five in the United States (12)] have caused confusion in the nomenclature of barnyardgrass. In 1950, Hitchcock listed no fewer than 60 synonyms among four defined varieties of E. crus-galli. Other genera in which it has appeared include Panicum, Setaria, Milium, Pennisetum. Oplismenus, and Orthopogon (10). Other common names for barnyardgrass include watergrass, junglerice (a confusion with E. colonum), cock's foot, cockspur grass (12), barn grass, panicum (19), cock's foot panicum (5), and barnyard millet (1). Names such as cockspur grass probably preceded Linnaeus and likely influenced the plant's botanical names.
HISTORY AND USESBarnyardgrass is native to Eurasia. No one apparently documented the migration of bamyardgrass into the United States; this may indicate that there was no interest in the plant as a weed or as possible forage until later. As of 1859, barnyardgrass was being tested as a forage, but was generally considered useless (though not ruinous as yet) (5). Some varieties were recommended for forage; var. frumentaceae was advertised by U.S. seedsmen as 'billion-dollar grass' for this purpose. Barnyardgrass has some forage value but requires considerable water to produce well and is too succulent for hay (10). However, barnyardgrass has been used for nourishing sheep in Australian drought mitigation programs (15). Toxic quantities of nitrates have been measured in barnyardgrass (14), though these are not usually of concern. Like most grasses, bamyardgrass produces edible seeds which can be ground into meal or flour and made into mush or bread (9). The size and abundance of these seeds make it perhaps inevitable that it has occasionally been cultivated as a grain. The barnyardgrass variety frumentaceae, described by William Roxburgh (1751-1815), is called Japanese millet, sanwa millet, or Japanese barnyard millet (1). [Frumentum is Latin for grain (20).] These or similar varieties are cultivated for cereal in Japan, the East Indies (9), tropical Asia, and Africa (10).
Barnyardgrass is found in 36 crops worldwide. It is the world's principal weed of rice, and is particularly serious in this crop in Australia, Brazil, Ceylon, Chile, Greece, Indonesia, Iran, Italy, Japan, Korea, Philippines, Portugal, Spain, and Taiwan. It is among the three worst weeds in cotton in Australia, USSR, and Spain; in corn in Australia and Yugoslavia; and in sugarbeets in the United States. It is a principal weed in many other crops and countries - rice, cotton, corn, and potatoes, for example, in the United States (12). Barnyardgrass has similar ecological preferences to rice, and young plants look similar (21); several thou-sand years of intensive handweeding of rice in Asia may have selected for rice mimicry (2). Many plants infesting rice fields may be transplanted in by accident (12).
Heavy infestations may remove 60 to 80% of the nitrogen from the soil (12), as well as considerable amounts of other macronutrients (15). Fertilizer applications favor the weed over rice (12). E. crus-galli is also a host to many viruses of rice and other grass crops (12). It is a host of Striga asiatica, which infests sorghum, corn, millet, sugar-cane, rice, and tobacco in India, Africa, and the United States (13).
Heavy infestations reduce rice tillering by 50%, and also reduce the number of panicles, height, weight of grains, and number of grains per panicle; rice yields may be reduced by 2000 to 4000 kg ha-1 (12). Barnyardgrass has been proven to reduce the yields of potatoes (3), snap beans (16), corn (7), grain sorghum (8), sugarbeets, green peas, and melons (18). Barnyardgrass interferes with harvesting of row crops and increases labor costs: the crop must be separated from the weed clumps (15). Tough, fibrous barnyardgrass plants, often still green and growing through-out bean plant senescence, can cause breakage of machinery in bean harvests and drag clods into the equipment.
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