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aerial pathogens: it refers to antagonistic microorganisms, which inhibit numerous fungal pathogens of aerial plant parts, e.g., Tilletiopsis ssp. parasitizes the cucumber powder mildew fungus Spaerotheca fuligena; they are present in the crop soils and exert a certain degree of biological control over one or many plant pathogens phyt >>> biological control

African cassava mosaic virus (ACMV): this disease continues to be the major constraint to both the commercial and subsistence production of cassava across central and southern Africa, causing up to 100 % crop losses; the causative agent of the disease has been shown to be a geminivirus of the Begomovirus phyt

Agrobacterium rhizogenes: a species of Gram-negative, rod-shaped soil bacteria, often harboring large plasmids, called Ri plasmids, it can cause a tumorous growth known as hairy root disease in certain plants bot biot >>> Figure 27

Agrobacterium tumefaciens: a species of soil bacteria, which can infect the stem of many plants and form crown gall tumors when it contains a Ti plasmid bot biot >>> Figure 27

Alternaria: a genus of fungi; it forms yellowish-brown conidia that are divided by transverse and longitudinal septa; there are many species, including important plant pathogens (early blight of potato, Alternaria solani; black rot of carrot and rape, A. radicina and A. brassica; Alternaria of wheat) phyt

anthracnose: a general term for any of several plant diseases in which symptoms include the formation of dark and often sunken spots on leaves, fruits etc., e.g., caused by Colletotrichum lindemuthianmum in dwarf bean, Elsinoe ampelina in grape, Kabtiella caulivora in clover, Gloeosporium ribis glossulariae in gooseberry, in linseed Colletotrichum linicolum, C. oligochaetum in cucumber, in rye and maize C. graminicolum or in melons C. orbiculare phyt

apple scab (Venturia inaequalis): a common disease of apple trees in which the most obvious symptom is the appearance of superficial, dark, corky scabs on the fruit; it is one of the most damaging diseases affecting commercial apple production; some wild Malus species possess resistance against apple scab; one gene, HcrVf2, from a cluster of three genes derived from the wild apple Malus floribunda, clone 821, has recently been shown to confer resistance to apple scab when transferred into a scab-susceptible variety phyt

bacterial blight disease: a plant disease spread by bacteria which causes death of leaves, spotting of bean pods and discoloration of seed; e.g., in rice, the causal agent is Xanthomonas oryzae var. oryzae; symptoms are lesions usually starting near the leaf tips or leaf margins or both, and extend down the outer edge; young lesions are pale to grayish green, later turning yellow to gray (dead) with time; in very susceptible varieties, lesions may extend to the entire leaf  length into the leaf sheath phyt

bacterial blight disease: a plant disease spread by bacteria which causes death of leaves, spotting of bean pods and discoloration of seed; e.g., in rice, the causal agent is Xanthomonas oryzae var. oryzae; symptoms are lesions usually starting near the leaf tips or leaf margins or both, and extend down the outer edge; young lesions are pale to grayish green, later turning yellow to gray (dead) with time; in very susceptible varieties, lesions may extend to the entire leaf length into the leaf sheath phyt

Bakanae disease: seedling disease of rice caused by fungus producing gibberellins phyt >>> gibberellin

bean dwarf mosaic virus (BDMV): it is a single-stranded DNA virus (genus: Begomovirus, family: Geminiviridae) that infects common bean (Phaseolus vulgaris) and causes stunted plant growth, and mosaic and mottle symptoms in leaves; BDMV shows differential pathogenicity in common bean, infecting germplasm of the Andean gene pool (e.g., the snap bean cultivar “Topcrop”), but not that of the Middle American gene pool (e.g., the pinto bean cultivar “Othello”); e.g., resistance to BDMV in “Othello” is associated with development of a hypersensitive response in vascular (phloem) tissues phyt

barley yellow dwarf virus (BYDV): it infects all cereal species but barley and oats are usually more severely affected than wheat; plants are most vulnerable to infection early in growth; infection results in stunting, discoloration and substantial yield loss; the virus is transmitted by several species of cereal aphids (mainly bird-cherry aphid, Rhopaosiphum padi, or grain aphid, Sitobion avenae) phyt >>> aphid vector

Bayoud disease (of date palm): a vascular wilt caused by the fungus Fusarium oxysporum f. sp. albedinis in the dioecious monocotyledonous date palm phyt

bean pod weevil (Apion godmani): a serious insect pest of common beans (Phaseolus vulgaris) grown in Mexico and Central America that is best controlled by host-plant resistance, e.g., available in the varieties “Durango” or “Jalisco” hort phyt

bean yellow dwarf virus (BYDV): a disease occurring in French bean, that can cause up to 90 % losses in yield phyt

bird cherry-oat aphid >>> barley yellow dwarf virus

black leg (of beets): a number of diseases (e.g., caused by Pythium debaryanum) in which symptoms include blackening of the base of the stem, often followed by the collapse of the stem phyt

black leg (of potato): a bacterial disease (Erwinia carotovora ssp. atroseptica) causing severe yield loss, particularly in wet conditions phyt

black sigatoka (in banana): a leaf spot disease, which is also known as black leaf streak, causes significant reductions in leaf area, yield losses of 50 % or more, and premature ripening, a serious defect in exported fruit; it is more damaging and difficult to control than the related yellow Sigatoka disease, and has a wider host range that includes the plantains and dessert and ABB cooking bananas that are usually not affected by yellow Sigatoka;  black sigatoka was first recognized in the Sigatoka Valley of Fiji in 1963, but was probably widespread in Southeast Asia and the South Pacific by that time; in the western hemisphere, it first appeared in 1972 in Honduras and now occurs on the mainland from central Mexico south to Bolivia and northwestern Brazil, and in the Caribbean basin in Cuba, Jamaica, the Dominican Republic and southern Florida; in Africa, the disease was first recorded in Zambia in 1973 and has since spread throughout the sub-Saharan portions of that continent; in most areas, black sigatoka has now replaced yellow sigatoka to become the predominant leaf spot disease of banana; the disease is caused by the ascomycete, Mycosphaerella fijiensis Morelet [anamorph: Paracercospora fijiensis (Morelet) Deighton] (a variant of the pathogen, M. fijiensis var. difformis , that was previously reported in tropical America, is no longer recognized); he pathogen produces conidia and ascospores, both of which are infective; they are formed under high moisture conditions, and are disseminated by wind, and in the case of conidia, also by rain and irrigation water; due to their greater abundance and small size, ascospores are more important than conidia in spreading the disease within plants and plantations; in contrast, infected planting material and leaves, which are used often in the developing world as packing materials, are usually responsible for the long-distance spread of the disease; the recent outbreak of black sigatoka in South Florida almost certainly resulted from the importation of infected germplasm by local growers; chemical control of first yellow, and then black sigatoka has evolved considerably over the last 65 years; Bordeaux mixture, first used in the mid-1930s, has been replaced by several succeeding generations of protectant and, later, systemic fungicides; presently, a sterol biosynthesis inhibitor, tridemorph, several different sterol demethylation inhibitors, most importantly propiconazole, and the methoxyacrylate, azoxystrobin, are the most commonly used systemics; since there is a tendency for resistance or tolerance to develop in M. fijiensis towards the systemic fungicides, they are usually applied in combination or alternation with broad-spectrum, protectant fungicides, such as the dithiocarbamates and chlorothalonil; with the exception of chlorothalonil, these fungicides are usually mixed with petroleum-based spray oils; the oils themselves are fungistatic and retard the development of the pathogen in the infected leaf; when they are mixed in water emulsions with fungicides, the resulting “cocktails” provide superior disease control; in export plantations, black sigatoka is controlled with frequent applications of fungicides and cultural practices, such as the removal of affected leaves, and adequate spacing of plants and efficient drainage within plantation; in total, these are very expensive fungicide, e.g.,  application includes the use of airplanes or helicopters, permanent landing strips and facilities for mixing and loading the fungicides, and the high recurring expense of the spray materials themselves; in total, it has been estimated that the costs of control are ultimately responsible for 15-20 % of the final retail price of these fruit in the importing countries; their great expense makes them essentially unavailable to small-holder farmers who grow this crop, it is these producers who are affected most by this important disease phyt

blight: it refers to a disease characterized by rapid and extensive death of plant foliage, and applied to a wide range of unrelated plant diseases caused by fungi, when leaf damage is sudden and serious; e.g., fire blight of fruit trees, halo blight of beans, potato blight etc. phyt

blotch: it refers to a disease characterized by large and irregular in shape, spots or blots on leaves, shoots, and stem phyt agr

broom: it refers to a symptom in which lateral branches proliferate in a dense cluster on the main branch (e.g., witch’s broom) phyt agr hort

bunt: stinking smut; a seed-borne disease of grasses caused by Tilletia ssp.; the grain is replaced by masses of fungal spores that have a characteristic fishy smell phyt

cadang-cadang disease (of coconuts): a lethal disease in the Philippines, caused by a viroid; this disease should be considered a grave phytosanitary risk in all other coconut areas phyt

canker: a plant disease in which there is sharply-limited necrosis of the cortical tissue, e.g., in apple; in rape, it causes leaf spotting over winter and cankers on the stem later; the latter are the more serious and appear after flowering caused by Leptosphaeria maculans, asexual stage Phoma lingam phyt

cauliflower mosaic virus (CaMV): a virus that infects cauliflower and other Cruciferae; it is transmitted by insects; the genome size is about 8 kb; it consists of double-stranded DNA with some single-stranded segments; in molecular genetics, it is used as a vector for transformation experiments phyt gene biot

Cercospora leaf spot disease: a disease found in sugarbeet caused by the fungus Cercospora beticola phyt

citrus tristeza virus (CTV): one of the most important citrus pathogens; it causes the death of millions of trees grafted on sour orange (Citrus aurantium); however, this rootstock is very well adapted to the Mediterranean, semi-arid conditions; some species confer resistance, e. g., Poncirus trifoliata phyt

clubroot (disease of crucifers): this soil-borne disease, present in many Brassica species, causes swollen and distorted roots by the fungus Plasmodiophora brassicae phyt

coffee berry disease (CBD): it is quite the most serious disease of coffee, and it is caused by the fungus Colletotrichum coffeanum; at present it is confined to eastern Africa; the fungus resides in the bark and parasitizes the berries only; in a susceptible tree, there is a total loss of all berries several months before harvest, and this represents the minimum level of horizontal resistance; in resistant trees selected recently in Ethiopia, there is no loss of berries, and this represents the maximum level of horizontal resistance; in other countries where the disease occurs, it is controlled with fungicides phyt

coffee leaf miner: it is a serious pest in coffee caused by Perileucoptera coffeella phyt

coffee leaf rust: the disease (Hemileia vastatrix) is of interest because, when arabica coffee was taken as one pure lines to the New World, all of its pests and diseases were left behind in the Old World; this gave Latin America a commercial advantage and it now produces about 80% of the world’s coffee; when the rust was accidentally introduced into Brazil in 1970, there were fears of a major disruption of the world supply; this disease is an apparent exception to the rule that vertical resistance will evolve only in the seasonal tissue of a discontinuous pathosystem; because coffee is an evergreen perennial phyt >>> http://www.globalrust.org/traction?type=home&proj=*

Colorado potato beetle:a parasite (Leptinotarsa decemlineata) of the wild Solanum rostratum (buffalo burr, or prickly potato) in Colorado, USA; this beetle moved on to cultivated potatoes as a new encounter parasite, and became one of the worst insect pests in the whole of agriculture; it is a yellow and black striped beetle, the same shape as a ladybird, but much larger, being half an inch long; the larvae and beetles are voracious eaters of potato leaves and, if not controlled, they can destroy a potato crop; originally controlled with compounds of lead and arsenic, the beetles are now controlled with synthetic insecticides phyt

common scab (of potato): a fungal disease (Streptomyces scabies) affecting the tuber skin; diseased tubers are unattractive but yield and cooking quality remain unaffected phyt

corky root rot (of tomato): a disease caused by Pyrenochaeta lycopersici phyt

crown gall: a common and widespread plant disease, which can affect a very wide range of woody and herbaceous plants (fruit trees, roses, etc.); it is caused by the bacterium Agrobacterium tumefaciens; galls are formed at the crown (stem-root junction) or, less frequently, on roots, stems, or branches phyt

CTV >>> citrus tristeza virus

cucumber mosaic virus (CMV): one of the most widely occurring plant viruses; infects more than 800 plant species and has a considerable negative impact on agriculture worldwide; in addition to an RNA genome, certain strains of CMV naturally harbor an RNA of 330-400 nucleotides, called sat-RNA, that depends on the virus for its entire cycle, has no significant similarity with the viral genome, and apparently does not encode protein; sat-RNAs are capable of attenuating CMV strains, resulting in a sharp decrease in virus titer in infected plants and an almost complete lack of symptoms (e.g., lethal tomato necrosis) phyt

damping-off: a disease of young seedlings in which the stems decay at ground level and the seedlings collapse; by planting in sterile soil, treating seeds with a fungicide, or soaking the soil with a fungicide it can be prevented, as avoiding overwatering and planting warm-season plants in cold soil phyt

downy mildew (of rape): the most common rapeseed disease (Peronospora parasitica); it causes yellow discoloration of the upper leaf surface and white fungal growth on the lower surface; though most severe in the autumn, the disease can reach high levels in cool wet springs; severe infections limit the ability of small plants to respond to good growing conditions phyt

dry rot: a disease characterized by the formation of dry, shriveled lesions, often caused by the fungus Phoma lingam phyt

ear rot (in maize) - Kolbenfäule (beim Mais): caused by different Fusarium spp. are one of the most dangerous food and feed safety challenges in >>> maize production; at present, the majority of the >>> inbreds and hybrids are susceptible; Gibberella and Fusarium ear rots (caused by F. graminearum and F. verticillioides, resp.) are the two main diseases, but more than 10 further Fusarium spp. cause ear rots; natural infection is initiated by a mixture of the local Fusarium spp., but usually one species predominates; breeders rely on natural infection to create sufficient levels of disease severity for selection-resistant genotypes; significant differences in genotypic resistance after >>> inoculation exist; resistance to the two major modes of fungal entry into the ear, via the silk or through kernel wounds, is not correlated in all genotypes; both native and exotic sources of resistance are under investigation; inbreds differ in general and specific combining ability for ear rot resistance; the >>> expression of resistance to disease severity and resistance to toxins is often used as synonyms; higher resistance to visual disease severities mostly results in lower toxin contamination; the mode of inheritance of resistance appears to differ: additive, possibly non-additive effects, digenic (dominant) and polygenic patterns have been identified phyt

ergot - Mutterkorn n: a disease that affects many grasses, including cereals; the conspicuous, hard, black sclerotia of the fungus (Claviceps purpurea) replace the ovaries (i.e., the grain in the spikelet of an infected plant); the germination of the sclerotia takes place after overwintering, the ascospores, from perithecia in stalked capitula (stromata), causing infection of the stigmas of susceptible plants; in the sphacelia stage, which comes after infection, there is a sweet liquid or nectar with an attraction for the insects, which take the conidia from plant to plant; later in the year the life cycle is completed by the development of sclerotia; the sclerotium contain alkaloids, which can cause severe poisoning or even death if ingested by animals or humans; most ergot for medicine comes from naturally or artificially diseased rye; it is chiefly of use in gynecology and obstetrics; its properties are dependent on a number of alkaloids of which ergotamine and ergotoline are the most important physiologically phyt >>> Picture 006 >>> rye

eyespot disease (of wheat, barley, rye, Pseudocercosporella syn Cercosporella herptotrichoides, of maize, Kabatiella zeae): common in autumn-sown wheat and barley; early symptoms appear as brown smudges on the leaf sheath below the first node; the lesions develop to become eye-shaped with diffuse brown margins and paler centers, which may carry black dots in their center; severe infections girdling the stem may result in premature ripening and white heads and weaken the stem to cause straggling and lodging phyt >>> Tapesia yallundae >>> Figure 30

fangy root (of beets): forked roots (in beets) caused by diseases, soil, or weather conditions agr phyt

fire blight (Erwinia amylovora): a disease of fruit trees, especially of pears and apples that blackens the foliage and is caused by bacterium; it is one of the most destructive diseases of apple (Malus ssp.) worldwide; no major, qualitative gene for resistance to this disease has been identified to date in apple phyt

frost mold: certain strains of at least three species of epiphytic bacteria (Pseudomonas syringae, P. fluorescens, Erwinia herbicola), are present on many plants; they serve as ice-nucleation-active catalysts for ice formation at temperatures as high as –1°C phyt

Fusarium ear blight: all cereals may be infected during wet warm weather at flowering; the disease is most common in wheat; it starts with small brown spots on the glumes, which develop to leave florets or whole spikelets prematurely bleached; pink or orange colonies of the fungus can often be seen at the base on the spikelet phyt


Fusarium wilt (of melon, Fusarium oxysporum f. sp. melonis): it causes serious economic losses in melon (Cucumis melo); two dominant resistance genes have been identified, Fom1 and Fom2, which provide resistance to races 0 and 2 and races 0 and 1, respectively, however Fusarium race 1.2 overcomes these resistance genes; a partial resistance to Fusarium race 1.2 that has been found in some Far East accessions is under polygenic control phyt

gall: a localized proliferation of plant or parasite tissue that produces an abnormal growth or swelling, usually caused by pathogenic organisms, nematodes, or insects phyt

gall midge: any midge of the family Cecidomyidae, the larvae of which form characteristic galls on plants zoo phyt

gangrene of potato: necrosis or death of soft tissue due to obstructed circulation, usually followed by decomposition and putrefaction (Phoma exigua var. foveata) phyt

geminivirus: a single-stranded DNA virus that causes serious diseases in cereals, vegetables and fiber crops worldwide; similar as nanoviruses it is transmitted by either whiteflies or leafhoppers; whitefly-transmitted geminiviruses are all in the genus Begomovirus, which typically have bipartite genomes (DNA A and DNA B) comprising circular DNAs of ~2,700 nucleotides, although some have been shown to be monopartite, having only a DNA A component; in contrast, the nanoviruses are a recently established group of plant viruses that are transmitted by either aphids or planthoppers, and have multipartite genomes comprising circular DNAs of ~1,000 nucleotides phyt

gigantism: it refers to abnormal overdevelopment due to an increase in cell size (hypertrophy), e.g., in roots of crucifers infected with club root (Plasmodiophora brassicae), or abnormal overdevelopment as a result of an increase in the number of cells in response to a disease-production agent (hyperplasia), e.g., witches broom, cankers, galls, leaf cure or scab phys phyt

green rice leafhopper (Nephotettix cincticeps): one of the most serious insect pests affecting cultivated rice (Oryza sativa) in temperate regions of East Asia; an accession of the wild rice species, O. rufipogon,  was found to be highly resistant to the insect by an antibiosis test  phyt

hairy root disease: a disease in some dicots; root-like tissue is proliferated along segments of the stem; it is caused by Agrobacterium rhizogenes, if it carries a Ri plasmid phyt biot

herbarium beetle: it (Cartodere filum) eats the spores of certain fungi, e.g., Lycoperdon, smuts etc., which are attached to the plant material of a herbarium phyt

honeydew: a sticky exudate containing conidia, which is produced during one stage of the life cycle of the fungus Claviceps purpurea phyt bot >>> ergot

insect herbivory: plant damage by certain insects (e.g. fall armyworm, Spodoptera frugiperda); it is responsible for about 15 % of the world's crop losses each year phyt

karnal bunt: a fungus disease of, for example, wheat that reduces yields and causes an unpalatable but harmless flavor in flour milled from infected grains phyt

late blight, foliage blight, tuber blight (of potato): a widespread and serious disease (Phytophthora infestans) affecting the potato and related species; symptoms include the appearance of brown patches on the leaves, often with white mold on the underside; under damp conditions the entire foliage may collapse; brown lesions also develop on tubers, spreading to involve the entire tuber in a dry brown rot; it reduces yields and marketability and may cause losses in store by encouraging soft rotting phyt

leaf blight: various diseases that lead to the browning and dropping of leaves phyt >>> late blight

leaf blight ((of maize): one of the most important foliar diseases of maize caused by the fungus Helminthosporium maydis; it is wide spread in tropical and subtropical parts of the world; there are two races; the ‘O’ race is more prevalent; the ‘T’ race caused heavy damage in USA during the 70th of last century; the inheritance of resistance  to race ‘O’ follows two patters; when resistance is expressed in number of lesions or percentage of leaf area infested, the expression is quantitative and gene action is additive with quite a high heritability; however, when resistance is in the form of lesion type then there is a qualitative expression; but polygenic resistance is more common  phyt

leaf miner: various insects, which, in the larval stage, produce a tunnel through leaves, feeding on the tissue, and leaving conspicuous traces of their paths phyt

leaf spot: it refers to various plant diseases that cause well-defined areas of tissue to die, creating noticeable spots phyt

leafy spurge: a member of the spurge family native in Europe and Asia; it is characterized by plants containing a white milky sap and flower parts in three's; leafy spurge is an erect, branching, perennial herb 2 to 3½ feet tall, with smooth stems and showy yellow flower bracts; stems frequently occur in clusters from a vertical root that can extend many feet underground; the leaves are small, oval to lance-shaped, somewhat frosted and slightly wavy along the margin; the flowers of leafy spurge are very small and are borne in greenish-yellow structures surrounded by yellow bracts; clusters of these showy, yellow bracts open in late May or early June, while the actual flowers do not develop until mid-June; it displaces native vegetation in prairie habitats and fields through shading and by usurping available water and nutrients and through plant toxins that prevent the growth of other plants underneath it; it also became an aggressive invader and, once present, can completely overtake large areas of open land; it occurs also across much of the northern U.S., with the most extensive infestations reported for Montana, North Dakota, Nebraska, South Dakota, and Wyoming; it has been identified as a serious pest; it was transported to the U.S. possibly as a seed impurity in the early 1800s; first recorded from Massachusetts in 1827, leafy spurge spread quickly and reached North Dakota within about 80 years; because of its persistent nature and ability to regenerate from small pieces of root, leafy spurge is extremely difficult to eradicate; biological control offers a highly promising management tactic for leafy spurge; the U.S. Department of Agriculture has shown success using six natural enemies of leafy spurge imported from Europe; these include a stem and root-boring beetle (Oberea erythrocephala), four root-mining flea beetles (Aphthona spp.) and a shoot-tip gall midge (Spurgia esulae); large scale field-rearing and release programs are carried out cooperatively by federal and State officials in many northern states; several systemic herbicides have been found to be effective if applied in June, when the flowers and seeds are developing, or in early to mid-September, when the plants are moving nutrients downward into the roots; Euphorbia esula (Euphorbiaceae) phyt

light leaf spot (of rape, Pyrenopeziza brassica, asexual stage Cylindrosporium concentricum): it appears as light green or bleached areas on the leaves; small white spore masses bordering the lesions phyt

loose smut: a disease of plants caused by a fungus of the Ustilaginales in which the masses of spores are exposed at maturity and can be dispersed freely by wind phyt

maize streak virus (MSV): a geminivirus, which has a single-stranded DNA genome that replicated in the nucleus of the host cells to provide a double-stranded replication intermediate and transcription template phyt

mildew: a plant disease in which the pathogen is seen as a growth on the surface of the host; a powdery (true ~) mildew is caused by one of the Erysiphaceae; a downy mildew (false ~) by one of the Peronosphaceae; the first may be controlled by sulfur, the second by copper; latest research showed that even milk of concentration 1 : 9 can have similar effects, at least in cucumber and grape vine phyt

mites: very small insects of the genus Arachnida, which includes spiders; they occur in large numbers in many organic surface soils or as pest on plants; they are not an important problem, possibly with the exception of the wheat curl mite, which is a vector of wheat streak mosaic virus (WSMV) zoo phyt >>> acarides

mold: any profuse or woolly fungus growth on damp or decaying matter or on surfaces of plant tissue phyt; any fungus of “moldy” appearance (i.e., with abundant, visible, woolly mycelium upon which dusty or powdery conidia can be seen); for example, anther mold of clover (Botrytis anthophila), black mould (Aspergillus niger), blue mold (Penicillium spp.) of apple (P. expansum), of citrus (P. italicum), of tobacco (Peronospora tabacina), bread mold (Monilia sitophilo), green mold of citrus (Penicillium digitatum), gray mold (Botrytis cinera), snow mold (Calonectria nivalis), tomato leaf mold (Cladosporium fulvum), or white mold of sweet pea (Hyalodendron album) phyt

mottled leaf: disease caused by a zinc deficiency that reduces the size of leaves and fruits (e.g., in citrus plants) phyt phys

mummy: a dried, shriveled fruit or seed colonized by a fungus or parasite phyt

net blotch disease (of barley): an important disease of winter barley (Pyrenophora teres, syn Helminthosporium teres, syn Drechslera teres); it is favored by cool, damp conditions; diseased leaves bear short, dark brown stripes or blotches consisting of a fine network of lines, running at right angles to as well as parallel to the veins; the blotches are usually surrounded by a narrow yellow zone phyt

Orobanchaceae: a family of totally parasitic herbs; often, specific root parasites of particular angiosperms and/or crop plants (e.g., sunflower) bot phyt

Panama disease (of banana): a verydestructive parasite in banana (Fusarium oxysporum f.sp. cubense) phyt

PIERCE’s disease (of grape): caused by the bacterium Xylella fastidiosa hort phyt

pest: any form of plant or animal life, or any pathogenic agent, injurious or potentially injurious of plants or plant products phyt

Phoma black stem disease (in sunflower): it caused by Phoma macdonaldii; it is one of the most important diseases of sunflower, e.g., in France phyt

phylloxera: a fatal vine pest that destroys the soft vine roots of Vitis vinifera cultivars; the only remedy is to replant on phylloxera-resistant rootstocks; roots of most American hybrid vines are immune to the effects of the pest; phylloxera will generally not inhabit soils that are 80 % sand; in all other soil textures, cultivars should be grafted onto phylloxera-resistant rootstocks hort >>> vine-louse

plant gall >>> cecidium

plum pox virus: a disease of plum and related trees whose symptoms are variable according to the plant species, but which usually include the appearance of pale or dark rings or spots on leaves and fruits phyt

potato cyst nematode (PCN): a major pest of potato (Globodera rostochiensis [golden PCN] + G. pallida [white PCN]) causing severe yield loss if populations are allowed to reach high levels zoo phyt

potato leaf roll virus (PLRV): a virus spread by aphids that can cause severe reduction in yield phyt

potato virus Y: a virus spread by aphids that can cause severe reduction in yield phyt

pyricularia leaf spot disease (of pearl millet): on of the two most-destructive diseases to pearl millet in the USA caused by Pyricularia grisea phyt

red rust: uredospore state of rusts, particularly of cereals phyt >>> http://www.globalrust.org/traction?type=home&proj=*

rhizomania (in beets): it is one of the most devastating diseases in sugar beet, is caused by Beet Necrotic Yellow Vein Virus (BNYVV) belonging to the genus Benyvirus; the use of sugar beet varieties with resistance to BNYVV is generally considered as the only way to maintain a profitable yield on rhizomania-infested fields; as an alternative to natural resistance, the transgenic expression of viral dsRNA for engineering resistance to rhizomania can be considered; transgenic plants expressing an inverted repeat of a 0.4 kb fragment derived from the BNYVV replicase gene displays high levels of resistance against different genetic strains of BNYVV when inoculated using the natural vector, Polymyxa betae; the resistance is maintained under high infection pressures and over prolonged growing periods in the greenhouse as well as in the field; resistant plants accumulated extremely low amounts of transgene mRNA and high amounts of the corresponding siRNA in the roots, illustrative of RNA silencing as the underlying mechanism; the transgenic resistance compared very favourably to natural sources of resistance to rhizomania and thus offers an attractive alternative for breeding resistant sugar beet varieties phyt meth biot

Rhynchosporium leaf blotch (of barley and rye): it frequently occurs in wet seasons and in high humidity; symptoms first appear as irregular or diamond-shaped blue-gray water-soaked lesions on the leaves and leaf sheathes; as the lesions mature, they become pale brown with a dark purple margin and coalesce to form large areas of dead tissue; ears may also be infected phyt

ringspot: a circular area of chlorosis with a green center; a symptom of many virus diseases phyt

root knot nematode: a nematode (Meloidogyne naasi) that induces small, gall-like growth on the roots of certain types of plants phyt

russet: it refers to a brownish roughened area on the skin of fruits as a result of cork formation phyt

rust: a plant disease caused by a fungus of the class Urediniomycetes; the characteristic symptom is the development of spots or pustules bearing masses of powdery spores that are usually rust-colored, yellow, or brown; stem rust in grasses was already described by the Roman philosopher Pliny (AD 100) as “the greatest pest of crops” phyt >>> http://www.globalrust.org/traction?type=home&proj=*

sawflies: larvae of various insects that feed on leaves phyt

scab - Schorf m: a general term for any unrelated plant disease in which the symptoms include the formation of dry, corky scabs, e.g., potato common scab is caused by the bacterium Streptomyces scabies, and potato powdery scab is cause by the fungus Spongospora subterranea phyt

scald: a necrotic condition in which tissue is usually bleached and has the appearance of having been exposed to high temperatures phyt

scale: any thin, scarious body, usually a degenerated leaf bot

scleroderris canker (of conifers): it is a very damaging disease of conifers caused by the fungal pathogen, Gremmeniella abietina var. `abietina'; this fungal pathogen is known to comprise a number of distinct races and biotypes -- in North America, two races, an indigenous North American race and an introduced European race, are present, in Europe, three distinct biotypes have been reported within the European race: one in the Alps, another in Fennoscandia, and a third that overlaps with the first two phyt

Sclerotinia (of rape or clover): a soil-borne disease (Sclerotinia sclerotiorum in rape, Sclerotinia trifoliorum in clover) that infects a wide range of crops; symptoms appear from May onward as bleached areas of the stem with black sclerotia within the infected stem phyt

SCN  >>> soybean cyst nematode

scorch: it refers to “burning” of leaf margins as a result of infection or unfavorable environmental conditions phyt

seed-born pathogens: carried on or in seeds; e.g., in wheat, the streak mosaic virus of barley, the fungi, such as snow mold (Fusarium nivale), Septoria spike blotch (Septoria nodorum), Helminthosporum leaf blotch or spot blotch (Cochiobolus sativus, Helminthosporum sativum syn Bipolaris sorokiana, Drechslera sorokiana), loose smut (Ustilago nuda or U. tritici), common smut or stinking smut (Tiletia caries), dwarf smut (Tiletia controversa), in barley the stripe mosaic virus, the fungi, such as snow mold (Fusarium nivale), leaf stripe disease (Pyrenophora graminea), Helminthosporum leaf blotch (Helminthosporum gramineum syn Drechslera graminea), net blotch disease (Pyrenophora teres syn Helminthosporum teres syn Drechslera teres), loose smut (Ustilago nuda), black smut (Ustilago nigra), hard smut (Ustilago hordei), in rye, the streak mosaic virus of barley, the fungi, such as snow mold (Fusarium nivale syn Griphosphaeria nivalis), Septoria spike blotch (Septoria nodorum), stalk bunt (Urocystis occulata syn Tuburcinia occulata), ergot (Claviceps purpurea), in oats, the streak mosaic virus of barley, the fungi, such as loose smut (Ustilago avenea), and in maize, the fungi, such as common smut (Ustilago maydis), seed rots (Fusarium ssp., Penicillium ssp.), seedling rots (Pythium ssp., Fusarium ssp., Helminthosporum ssp., Penicillium ssp., Rhizopus ssp., Rhizoctonia ssp., Deploida ssp.) phyt


Septoria seedling disease (of wheat): it is the same pathogen (Septoria nodorum syn Leptosphaeria nodorum), which causes Septoria glume blotch in wheat phyt

shot hole: a leaf spot disease characterized by holes made by the dead parts dropping out; e.g., caused by Heteropatella antirrhini in snapdragon, by Stigmina carpophila in peach or by Pseudomonas mors-prunorum in plum phyt

smut: a plant disease caused by a fungus of the order Ustilaginales; the symptoms include the formation of masses of black soot-like spores; infected plants often show some degree of distortion phyt >>> bunt

soft rot: a decomposition of plant tissue (fruits, roots, stem etc.) by fungi or bacteria resulting in a tissue becoming soft, e.g., caused by Erwinia carotovora in potato phyt

South American leaf blight (SALB): a disease of the rubber tree caused by the fungus Microcyclus ulei phyt

southern root-knot nematode: can cause severe yield loss of soybean in the southern production region of the USA; planting root-knot nematode-resistant cultivars is the most effective method of preventing yield loss, Meloidogyne spp. phyt

soybean cyst nematode (SCN): small roundworms, Heterodera glycines, that cause root damage and subsequent above-ground symptoms to soybeans, e.g. this nematode is found in 27 states in the USA and causes the greatest yield losses of any pathogen of soybeans; 16 physiological races of the nematode have been identified; management of SCN is achieved by planting resistant varieties to a given race or races and by rotating soybeans with a non-host crop such as field maize; nematicides can also be used to reduce populations phyt

stalk tunneling: it refers to the longitudinal tunnels in plant stalks produced by different insects phyt

stem rust (in wheat): a dangerous fungus (Puccinia graminis f. sp. tritici) causing yield loss in many country of the world; recently,a new and virulent race, previously found in East Africa and Yemen, has moved to major wheat growing areas in Iran; countries like Afghanistan, India, Pakistan, Turkmenistan, Uzbekistan and Kazakhstan are most threatened by that fungus it is estimated that as much as 80% of all wheat varieties planted in Asia and Africa are susceptible to the wheat stem rust; the spores of wheat rust are mostly carried by wind over long distances; the fungus is spreading rapidly and could seriously lower wheat production in countries at direct risk; the new race first emerged in Uganda in 1999 and is therefore called Ug99; subsequently it spread to Kenya and Ethiopia; in 2007, Ug99 has affected wheat fields in Yemen; disease surveillance and wheat breeding is already underway to monitor the fungus and to develop Ug99 resistant varieties phyt >>> http://www.globalrust.org/traction?type=home&proj=*

sudden-death syndrome (of soybean): a disease caused by Fusarium solani f. sp. glycines; it is controlled by a number of quantitatively inherited loci (QTLs); e.g., the variety “Forrest” shows a strong field resistance to the syndrome while the variety “Essex” is susceptible phyt

sugarbeet leaf curl: caused by the sugarbeet leaf curl virus phyt

sugarcane rust: it is of interest because no vertical resistance occurs against it; this is because sugarcane is derived from a continuous wild pathosystem; the disease has occasionally been damaging when it appeared in an area of susceptible cane, as happened recently in Cuba phyt >>> http://www.globalrust.org/traction?type=home&proj=*

sweet potato whitefly: an insect pest of cotton, fruit, vegetable, and greenhouse crops phyt

take-all disease: a fungal disease (Gaeumannomyces graminis syn Ophiobolus graminis) that attacks wheat plant roots; it causes dry rot and premature death of the plant; certain strains of Brassica plants and Pseudomonas bacteria act as natural antifungal agents against the fungus phyt >>> biological control

tan spot (of wheat): a disease of wheat that is caused by the fungus Pyrenophora tritici-repentis; on susceptible hosts, P. tritici-repentis induces two phenotypically distinct symptoms, tan necrosis and chlorosis; this fungus produces several toxins that induce tan necrosis and chlorosis symptoms in susceptible cultivars; there is a wheat variety “Salamouni”  that is resistant to tan spot disease, controlled by a single recessive gene “tsn4“ located on chromosome 3A phyt

Tapesia yallundae: sexual stage of Pseudocercosporella herpotrichoides phyt >>> white leaf spot >>> eyespot disease

thrips: any of several minute insects of the order Thysanoptera, that have long, narrow wings fringed with hairs and that infest and feed on a wide variety of weeds and crop plants zoo phyt

Valsa canker: one of the most destructive diseases in apple (Malusdomestica), especially in eastern Asia, Valsa ceratosperma phyt

vine-louse: a plant louse (Phylloxera vitifoliae) that injures the grapevine phyt

virescence: it refers to greening of tissue that is normally devoid of chlorophyll, e.g., the abnormal development of flowers in which all organs are green and partly or wholly transformed into structures like small leaves phyt

wart (of potato): the causal agent of potato wart (Synchytrium endobioticum) is an obligate parasitic chytrid fungus; it is included as a quarantine pathogen in 55 countries, with losses in susceptible cultivars reaching 50–100%; highly intraspecific variation of wart diseases resistance allows the selection of extremely resistant and susceptible genotypes available for future genetic and breeding studies phyt

whitefly: insects whose adults resemble tiny moths but are related to aphids; nymphs that suck sap and damage leaves of several Brassicaceae and other horticultural plants phyt

white leaf disease (of oats): caused by copper deficiency, often on peaty soils; can be compensated by application of copper sulfate (2 kg per 400 l water/ha) to leaves phyt

white leaf spot (of rape, Pseudocercosporella capsellae): characterized by large white spots with dark margins and gray-black centers in older lesions on leaves; pods can be similarly infected phyt >>> Tapesia yallundae

white mold (of bean): a major disease of common bean caused by the fungus Sclerotinia sclerotiorum phyt

white rust disease (of Indian mustard): it is caused by Albugo candida and a serious disease causing considerable yield loss every year in India  phyt

wilt: a type of disease in which wilting is a principal symptom phyt

witch’s broom: massed outgrowth of branches of woody plants caused by fungi, e.g., by rusts phyt

withertip: death of the leaf beginning at the tip, usually in young leaves phys

yellows: a plant disease characterized by yellowing and stunting of the host plant phyt

yellow sigatoka >>> black sigatoka

yellow spot disease (in sugarcane): caused by the fungus Mycovellosiella koepkei phyt

© by R. Schlegel 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019