Corn stunt disease is a bacterial disease of corn and other grasses. Symptoms include stunted growth and leaves turning red. It is caused by the bacterium Spiroplasma kunkelii . [1]
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Corn stunt disease is a bacterial disease of corn and other grasses. Symptoms include stunted growth and leaves turning red. It is caused by the bacterium Spiroplasma kunkelii . [1]
S. kunkelii, a spiroplasma often referred to as corn stunt spiroplasma, can survive and overwinter in the maize leafhopper ( Dalbulus maidis ), which infects corn plants in the spring and causes corn stunt disease. [2] [3] It has been reported in the San Joaquin Valley in California that volunteer plants are critical to help leafhoppers survive in the winter, where volunteer plants can give an extra two months of season to the leafhoppers. [3] This pathogen has been described as propagative persistent and circulative, accumulating and replicating in the vector where it has been found in the hemolymph, cells of the gut, and salivary glands of insect vectors. During feeding it is delivered to the phloem tissue of the host corn plant. [4] [5] [6] [7]
There is an important relationship that S. kunkelii has with D. maidis, where its survival over the winter depends on the survival of the leafhopper. [3] This relationship may also be beneficial for D. maidis. When Dalbulus leafhoppers are infected with S. kunkelii, it has been reported that fertility and life-expectancy are diminished. [6] However, specific to D. maidis, one study suggests that the presence of S. kunkelii increases chances of D. maidis survival in colder weather, specifically 10-20 degrees Celsius, when either given oats or lived on moist sand, although this effect on survival was not found to be true in the case of freezing temperatures. [8] Similarly, one group suggests that the spiroplasma may provide useful metabolites for its leafhopper vector. [6]
S. Kunkelii can be transmitted by other leafhopper genera, [9] however the leafhopper D. maidis is of most significance in Latin America. [10] [11] [9] [12] [13]
The most effective way to control corn stunt is early planting. Although corn stunt can impact corn planted in early months like April or March, the greatest damage affects corn planted after July. [2] Chemicals like insecticides can be used to control D. maidis, [14] [15] [16] however, the use of this method to control Corn Stunt is not very successful. [2] [16] In sweet corn, reflective mulches can be an effective way to control D. maidis and the disease it vectors, compared to insecticides. [17] Mulching should be performed early in the plant's development to properly control this disease, as greater damage happens if the plant host is younger when infected with corn stunt disease. [16] [17] Although D. maidis is the major vector for S. kunkelii, [12] one study calls for a focus on all vectors that can transmit corn stunt disease, since, in addition to D. maidis, three other species of Dalbulus are able to spread and carry corn stunt spiroplasma. [18]
S. kunkelii, the corn stunt spiroplasma, was characterized as the causative agent of corn stunt disease by Whitcomb et al. in 1986. [19] [20] In the literature, the combination of maize bushy stunt mycoplasma and maize rayado fino marafivirus in addition to S. kunkelii has been called the corn stunt disease complex, also called "achaparramiento." The combination of these diseases is devastating and all of these can be transmitted by D. maidis. Because of the pathogens and it can transmit, D. maidis is of great financial importance in Latin America. [21] [16] [22] [23] [11] [12] [9] [13] Also, maize chlorotic dwarf virus has also been reported to be implicated in corn stunt disease. [21] When corn stunt spiroplasma and maize bushy stunt mycoplasma may co-occur, the disease that they can cause has been referred to as "puca poncho" due to its red coloring of the diseased maize. [12] Different combinations of these pathogens are notably present and cause serious problems in yield production in Central America, reported in Nicaragua, [23] Peru, [12] and Argentina, [24] [25] and the southern part of the United States, where it was reported in California [3] and Florida. [26] [25] Despite the common co-occurrence with other causative agents, S. kunkelii is the most prevalent in the subtropics as the causative agent of corn stunt disease and can be quite devastating. [25] [24]
Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-like organisms. Since their discovery, phytoplasmas have resisted all attempts at in vitro culture in any cell-free medium; routine cultivation in an artificial medium thus remains a major challenge. Phytoplasmas are characterized by the lack of a cell wall, a pleiomorphic or filamentous shape, a diameter normally less than 1 μm, and a very small genome.
Acholeplasmataceae is a family of bacteria. It is the only family in the order Acholeplasmatales, placed in the class Mollicutes. The family comprises the genera Acholeplasma and Phytoplasma. Phytoplasma has the candidatus status, because members still could not be cultured.
Spiroplasma is a genus of Mollicutes, a group of small bacteria without cell walls. Spiroplasma shares the simple metabolism, parasitic lifestyle, fried-egg colony morphology and small genome of other Mollicutes, but has a distinctive helical morphology, unlike Mycoplasma. It has a spiral shape and moves in a corkscrew motion. Many Spiroplasma are found either in the gut or haemolymph of insects where they can act to manipulate host reproduction, or defend the host as endosymbionts. Spiroplasma are also disease-causing agents in the phloem of plants. Spiroplasmas are fastidious organisms, which require a rich culture medium. Typically they grow well at 30 °C, but not at 37 °C. A few species, notably Spiroplasma mirum, grow well at 37 °C, and cause cataracts and neurological damage in suckling mice. The best studied species of spiroplasmas are Spiroplasma poulsonii, a reproductive manipulator and defensive insect symbiont, Spiroplasma citri, the causative agent of citrus stubborn disease, and Spiroplasma kunkelii, the causative agent of corn stunt disease.
The glassy-winged sharpshooter is a large leafhopper, similar to other species of sharpshooter.
Paul Wilson Oman was an American entomologist and a specialist on leafhopper taxonomy.
Leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind legs are modified for jumping, and are covered with hairs that facilitate the spreading of a secretion over their bodies that acts as a water repellent and carrier of pheromones. They undergo a partial metamorphosis, and have various host associations, varying from very generalized to very specific. Some species have a cosmopolitan distribution, or occur throughout the temperate and tropical regions. Some are pests or vectors of plant viruses and phytoplasmas. The family is distributed all over the world, and constitutes the second-largest hemipteran family, with at least 20,000 described species.
The Auchenorrhyncha suborder of the Hemiptera contains most of the familiar members of what was called the "Homoptera" – groups such as cicadas, leafhoppers, treehoppers, planthoppers, and spittlebugs. The aphids and scale insects are the other well-known "Homoptera", and they are in the suborder Sternorrhyncha.
Aster yellows is a chronic, systemic plant disease caused by several bacteria called phytoplasma. The aster yellows phytoplasma (AYP) affects 300 species in 38 families of broad-leaf herbaceous plants, primarily in the aster family, as well as important cereal crops such as wheat and barley. Symptoms are variable and can include phyllody, virescence, chlorosis, stunting, and sterility of flowers. The aster leafhopper vector, Macrosteles quadrilineatus, moves the aster yellows phytoplasma from plant to plant. Its economic burden is primarily felt in the carrot crop industry, as well as the nursery industry. No cure is known for plants infected with aster yellows. Infected plants should be removed immediately to limit the continued spread of the phytoplasma to other susceptible plants. However, in agricultural settings such as carrot fields, some application of chemical insecticides has proven to minimize the rate of infection by killing the vector.
The beet leafhopper, also sometimes known as Neoaliturus tenellus, is a species of leafhopper which belongs to the family Cicadellidae in the order Hemiptera.
Karl Maramorosch was an Austrian-born American virologist, entomologist, and plant pathologist. A centenarian and polyglot, he conducted research on viruses, mycoplasmas, rickettsiae, and other micro-organisms; and their transmission to plants through insect vectors in many parts of the world. He is the co-author of a textbook on techniques in virology and is the author of numerous papers on the biology and ecology of plant viruses, their hosts, and vectors. He received the Wolf Prize in Agriculture in 1980 for his contribution to the study of crop pathogens.
The common brown leafhopper is one of the most common species of Australian leafhoppers with a very wide host range. It is an important vector of several viruses and phytoplasmas worldwide. In Australia, phytoplasmas vectored by O. orientalis cause a range of economically important diseases including legume little leaf, tomato big bud, lucerne witches broom, potato purple top wilt, Australian lucerne and the insect is a possible vector of Australian grapevine yellows. O. orientalis also transmits Tobacco yellow dwarf virus to beans, causing bean summer death disease and to tobacco, causing tobacco yellow dwarf disease.
Empoasca decipiens is a species of leafhopper belonging to the family Cicadellidae subfamily Typhlocybinae. The adults reach 3–4 millimetres (0.12–0.16 in) of length and a are homogenously green with whitish markings on its pronotum and vertex. E. decipiens is commonly referred to as the “green leafhopper” because of its colouration. The absence of clear stripes along the forewings can easily distinguish it from the similar leafhopper species E. vitis, but distinguishing it from other leafhoppers with the same colouration requires examination under a microscope. It is present in most of Europe, in the eastern Palearctic realm, in North Africa, in the Near East, and in the Afrotropical realm. Both nymphs and adults of this small insect are considered to be a very destructive pests on field crops, vegetables and greenhouse plants.
Rhopalosiphum maidis, common names corn leaf aphid and corn aphid, is an insect, and a pest of maize and other crops. It has a nearly worldwide distribution and is typically found in agricultural fields, grasslands, and forest-grassland zones. Among aphids that feed on maize, it is the most commonly encountered and most economically damaging, particularly in tropical and warmer temperate areas. In addition to maize, R. maidis damages rice, sorghum, and other cultivated and wild monocots.
Peregrinus maidis, commonly known as the corn planthopper, is a species of insect in the order Hemiptera and the family Delphacidae. It is widespread throughout most tropical and subtropical regions on earth, including southern North America, South America, Africa, Australia, Southeast Asia and China. P. maidis are a commercially important pest of maize and its relatives. In addition to physical plant damage, P. maidis is the vector for several species-specific maize viruses, including maize stripe virus, maize mosaic virus and the non-pathogenic Peregrinus maidis reovirus.
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Chandrashekaraswami Adiveyya Viraktamath is an Indian entomologist who specializes in the systematics of leaf-hoppers, Cicadellidae. He served as a professor of entomology at the University of Agricultural Sciences, Bangalore.
Spiroplasma kunkelii is a species of Mollicutes, which are small bacteria that all share a common cell wall-less feature. They are characterized by helical and spherical morphology, they actually have the ability to be spherical or helical depending on the circumstances. The cells movement is bound by a membrane. The cell size ranges from 0.15 to 0.20 micrometers.
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