Azadirachta indica, commonly known as neem, margosa, nimtree or Indian lilac, is a tree in the mahogany family Meliaceae. It is one of the two species in the genus Azadirachta. It is native to the Indian subcontinent and to parts of Southeast Asia, but is naturalized and grown around the world in tropical and subtropical areas. Its fruits and seeds are the source of neem oil. Nim is a Hindustani noun derived from Sanskrit nimba (निंब).
In botany, apical dominance is the phenomenon whereby the main, central stem of the plant is dominant over other side stems; on a branch the main stem of the branch is further dominant over its own side twigs.
Auxins are a class of plant hormones with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essential for plant body development. The Dutch biologist Frits Warmolt Went first described auxins and their role in plant growth in the 1920s. Kenneth V. Thimann became the first to isolate one of these phytohormones and to determine its chemical structure as indole-3-acetic acid (IAA). Went and Thimann co-authored a book on plant hormones, Phytohormones, in 1937.
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.
The axillary bud is an embryonic or organogenic shoot located in the axil of a leaf. Each bud has the potential to form shoots, and may be specialized in producing either vegetative shoots or reproductive shoots (flowers). Once formed, a bud may remain dormant for some time, or it may form a shoot immediately.
Phyllody is the abnormal development of floral parts into leafy structures. It is generally caused by phytoplasma or virus infections, though it may also be because of environmental factors that result in an imbalance in plant hormones. Phyllody causes the affected plant to become partially or entirely sterile, as it is unable to produce normal flowers.
This is a glossary of some of the terms used in phytopathology.
Moniliophthora perniciosa is a fungus that causes "witches' broom disease" (WBD) of the cocoa tree T. cacao. This pathogen is currently limited to South America, Panama and the Caribbean, and is perhaps one of the best-known cocoa diseases, thought to have co-evolved with cocoa in its centre of origin.
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.
Sugarcane grassy shoot disease (SCGS), is associated with 'Candidatus Phytoplasma sacchari' which are small, pleomorphic, pathogenic mycoplasma that contribute to yield losses from 5% up to 20% in sugarcane. These losses are higher in the ratoon crop. A higher incidence of SCGS has been recorded in some parts of Southeast Asia and India, resulting in 100% loss in cane yield and sugar production.
Taphrina pruni is a fungal plant pathogen of blackthorn that causes the pocket or bladder plum gall, a chemically induced distortion of the fruit (sloes), producing swollen on one side, otherwise deformed and flattened fruit gall without a stone. The twigs on infected plants may also be deformed with small strap-shaped leaves.
Virescence is the abnormal development of green pigmentation in plant parts that are not normally green, like shoots or flowers. Virescence is closely associated with phyllody and witch's broom. They are often symptoms of the same disease affecting the plants, typically those caused by phytoplasmas. The term chloranthy is also sometimes used for floral virescence, though it is more commonly used for phyllody.
Phomopsisblight of juniper is a foliar disease discovered in 1917 caused by the fungal pathogen Phomopsis juniperovora. The fungus infects new growth of juniper trees or shrubs, i.e. the seedlings or young shoots of mature trees. Infection begins with the germination of asexual conidia, borne from pycnidia, on susceptible tissue, the mycelia gradually move inwards down the branch, and into the main stem. Management strategies mainly include removing and destroying diseased tissue and limiting the presence of moisture on plants. Junipers become resistant to infection as they mature and the young yellow shoots turn dark green. Preventive strategies include planting only resistant varieties and spraying new growth with fungicide until plants have matured.
CandidatusPhytoplasma fraxini is a species of phytoplasma, a specialized group of bacteria which lack a cell wall and attack the phloem of plants. This phytoplasma causes the diseases ash yellows and lilac witches' broom.
Spruce broom rust or yellow witches' broom rust is a fungal plant disease caused by the basidiomycete fungus known as Chrysomyxa arctostaphyli. It occurs exclusively in North America, with the most concentrated outbreaks occurring in northern Arizona and southern Colorado on blue and Engelmann spruce, as well as in Alaska on black and white spruce. This disease alternates its life cycle between two hosts, with the spruce serving as the primary host and bearberry serving as the secondary or alternate host. The name for the disease comes from the distinctive “witches broom”, commonly yellow in color, which forms on the spruce after young needles have been infected. Management must be carried out through physical or mechanical methods, such as the pruning of brooms or the removal of the secondary host from the area, because no chemical control measures have yet been determined to be economically effective. Generally, spruce broom rust is seen as a mostly cosmetic issue, and it is very rarely the direct cause of tree death; however, research has shown a reduction in overall productivity and health of infected trees, making it an important issue for logging and timber companies.
Little leaf of brinjal is one of the most serious diseases of brinjal in the areas of its cultivation. "Brinjal" is a common name in some areas for the plant species Solanum melongena, the eggplant. The disease is known to cause heavy economic losses in India. As the name indicates, symptoms of the disease include shortening of the petioles and production of leaves which are much smaller in size than are normal for the species. Petioles are so short that leaves appear to be glued to the stem. They become soft, glabrous, somewhat yellow. Affected plants do not bear any flowers or fruits if infection is in early stages of plant growth. In cases of late season infections, fruits may remain small, become hard and unfit for consumption or marketing. The disease is caused by a plant pathogenic mollicute, Phytoplasma and is transmitted by the insect vector, Hishimonus phycitis which belongs to the group of leafhoppers.
Longan witches broom-associated virus is a species of positive-sense single-stranded RNA virus that has not been assigned to a genus within the family Potyviridae. It is thought to be the cause of witch's broom in longan, a large tropical tree from southeastern Asia of economic value. Longan witches broom disease is a condition that was first described in 1941. The virus was found in symptomatic plants and absent in healthy plants, but not all of Koch's postulates have been fulfilled.
Taphrina betulina is a fungal plant pathogen that causes the gall, witches broom, which is a chemical infection of birch buds or the developing shoots, leading to a proliferation of growth. It was first described by Emil Rostrup in 1883 and is found in Europe, New Zealand and North America.
