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Wheat yellow rust ("Puccinia striiformis" f.sp. "tritici"), also known as stripe rust, is one of the three wheat rust diseases principally found in wheat grown in cooler environments. Such locations are generally associated with northern latitudes or cooler seasons.
Sudden Death Syndrome (SDS) in Soybean plants quickly spread across the southern United States in the 1970s, eventually reaching most agricultural areas of the US. SDS is caused by a Fusarium fungi, more specifically the soil borne root pathogen "Fusarium virguliforme," formerly known as "Fusarium solani" f. sp. "glycines"."." Losses could exceed hundreds of millions of dollars in US soybean markets alone making it one of the most important diseases found in Soybeans across the US
Leaf rust of barley is considered a relatively minor disease in the United States. However, sporadic outbreaks have occurred in the southeastern and Midwestern regions of the country.
Leaf rust is a fungal disease of barley caused by "Puccinia hordei". It is also known as brown rust and it is the most important rust disease on barley.
Panama disease is a plant disease of the roots of banana plants. It is a type of Fusarium wilt, caused by the fungal pathogen "Fusarium oxysporum f. sp. cubense" (Foc). The pathogen is resistant to fungicide and cannot be controlled chemically.
During the 1950s, Panama disease wiped out most commercial Gros Michel banana production. The Gros Michel banana was the dominant cultivar of bananas, and the blight inflicted enormous costs and forced producers to switch to other, disease-resistant cultivars. New strains of Panama disease currently threaten the production of today's most popular cultivar, Cavendish.
As R.P. Singh, J. Huerta-Espino, and A.P. Roelfs say in their (undated) comprehensive review of literature on the wheat rusts for UN FAO:
"Although Gadd first described stripe rust of wheat in 1777, it was not until 1896 that Eriksson and Henning (1896) showed that stripe rust resulted from a separate pathogen, which they named P. glumarum. In 1953, Hylander et al. (1953) revived the name P. striiformis."
There are a number of control methods to prevent and reduce the Banana Freckle disease. The paper bag method seems to be the most effective way to gain physical control of the pathogen. The infected leaves are the primary source of spores, and placing a bag over the bananas, once harvested, creates a barrier to prevent inoculum from spreading to the fruit.
Some cultural controls include pruning out infectious plant material, planting in pathogen-free fields, and practicing proper sanitation techniques. In the Philippines, pruning and cutting out patches of infected tissue have prevented the spread of the pathogen in the plant during disease outbreaks. General sanitation practices have also reduced the spread of inoculum. When planters failed to maintain sanitary equipment, seeds, and soil, they witnessed severe fruit infections. The more freckles seen on the leaves of the plant, the more the fruit develops symptoms of the disease. Inversely, less freckles corresponded to less disease.
In addition, multiple fungicides have been seen to reduce Banana Freckle disease. In Hawaii, spraying the leaves and fruit with maneb (1 lb./100 gal water plus 4 oz of sticker-spreader) every 2 weeks or once a month throughout the year has remarkably reduced the spread of inoculum. In Taiwan, spraying fungicides, such as phaltan, orthocide, chlorothalonil, dithiocarbamates, and propiconazole, biweekly have produced effective results against the disease. In the Philippines, chemical controls used against Black or Yellow Sigatoka disease have been helpful. These consist of mancozeb, triazoles, tridemorph, and strobilurin. Mancozeb seems to be the most effective fungicide against Banana Freckle disease in Hawaii and the Philippines . These fungicides do not eliminate the pathogen completely, but they reduce the inoculum levels and eventually reduce yield loss.
Lastly, eradication of infected plants can prevent further infection of other fruit around the area.
Banana Freckle is a disease caused by the fungus "Guignardia musae" (telomorph) or "Phyllosticta musarum" (anamorph). Generally, the causal agent of disease is referred to as Guignardia-Phyllosticta sp. There are several different strains of the fungus that exist to infect different banana varieties around the globe. Symptoms include yellowing of the tissue and formation of small dark brown spots on the leaves and fruit. Within the spots, conidia or pycnidia can be found. Banana Freckle is easily propagated and spread from plant to plant by rain splash and movement of infected tissue or fruit. Management of the disease consists of cutting out infected leaves, the paper bag method, fungicide application, and proper sanitation techniques. This devastating disease is extremely relevant for the major banana exporting countries of the world. In the absence of chemical control, there is about a 78% yield loss. Banana Freckle disease needs to be carefully monitored in order to prevent further spread of the disease.
Cladosporium fulvum is an Ascomycete called "Passalora fulva", a non-obligate pathogen that causes the disease on tomato known as the Tomato leaf mold. P. fulva only attacks tomato plants, especially the foliage, and it is a common disease in the greenhouses, but can also occur in the field. The pathogen is likely to grow in humid and cool conditions. In the greenhouses, this disease causes big problems during the fall, in the early winter and spring, due to the high relative humidity of air and the temperature, that are propitious for the leaf mold development. This disease was first described in the North Carolina, by Mordecai Cubitt Cooke (1883), on cultivated tomato (Cooke 1883), although it is original from South and Central America. The causal fungus of tomato leaf mold may also be referred as Cladosporium fulvum (Cooke 1883), a former name.
Grey leaf spot (GLS) is a foliar fungal disease that affects maize, also known as corn. There are two fungal pathogens that cause GLS, which are "Cercospora zeae-maydis" and "Cercospora zeina" . Symptoms seen on corn include leaf lesions, discoloration (chlorosis), and foliar blight. The fungus survives in debris of topsoil and infects healthy crop via asexual spores called conidia. Environmental conditions that best suit infection and growth include moist, humid, and warm climates. Poor airflow, low sunlight, overcrowding, improper soil nutrient and irrigation management, and poor soil drainage can all contribute to the propagation of the disease. Management techniques include crop resistance, crop rotation, residue management, use of fungicides, and weed control. The purpose of disease management is to prevent the amount of secondary disease cycles as well as to protect leaf area from damage prior to grain formation. Corn grey leaf spot is an important disease of corn production in the United States, economically significant throughout the Midwest and Mid-Atlantic regions. However, it is also prevalent in Africa, Central America, China, Europe, India, Mexico, the Philippines, northern South America, and Southeast Asia. The teleomorph (sexual phase) of "Cercospora Zeae-Maydis" is assumed to be "Mycosphaerella sp."
Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. The pathogen that causes Fusarium wilt is "Fusarium oxysporum" ("F. oxysporum"). The species is further divided into forma specialis based on host plant.
The best way to manage SDS is with a resistant variety. One issue is that most resistant varieties are only partially resistant so yield reductions may still occur. Another issue is that the plant needs resistance for SDS and SCN in order to gain true resistance because of their synergistic relationship and most varieties do not have resistance for both. Aside from resistance, the only other ways to control SDS are management practices.
These include:
- Avoid planting in cool, wet conditions
- Plant later when the soil has warmed up
- Try avoiding soil compaction as it creates wet spots in the soil that can increase plant stress and SDS infection rates
- Managing for SCN as this nematode often occurs alongside "F. virguliforme"
- Deep tillage to break up compaction and help the soil warm faster
One common management tactic used in other pathogen management plans is crop rotation. In some cases, disease severity can be reduced but most often it is not effective. This is because of chlamydospores and macroconidia as they can persist in soils for many years.
Fungicides are another common product used to control fungal pathogens. In-furrow applications and seed treatments with fungicides have some effect in decreasing disease instance but in most cases, the timing isn't right and the pathogen can still infect the plants. Foliar applications of fungicides have no effect on disease suppression for SDS because the fungi are found in the soil and mainly the roots of the plants. Most foliar fungicides do not move downward through plants, therefore having no effect on the pathogen.
Velvet Blight is a disease that affects the stems, branches, leaves, fruits or trunks of plants and trees. This disease is primarily caused by three fungal species from the genus "Septobasidium": "S. bogoriense", "S. pilosum" and "S. theae".
It is known to affect mainly tea plants ("Thea" genus).
The most studied of these species is "S. bogoriense", most notably due to the work of Ernst Albert Gäumann. "S. bogoriense" is named after the Herbarium Bogoriense (Bogor, West Java, Indonesia) which is the place where it was first identified on the bark of an unspecified tree and named by E. Nyman on June 3, 1898. This species was also listed in Otto Warburg's Monsunia in 1900.
The first strategy of management is the cultural practices for reducing the disease. It includes adequating row and plant spacing that promote better air circulation through the canopy reducing the humidity; preventing excessive nitrogen on fertilization since nitrogen out of balance enhances foliage disease development; keeping the relatively humidity below 85% (suitable on greenhouse), promote air circulation inside the greenhouse, early planting might to reduce the disease severity and seed treatment with hot water (25 minutes at 122 °F or 50 °C).
Two external symptoms help characterize Panama disease of banana:
- Yellow leaf syndrome, the yellowing of the border of the leaves which eventually leads to bending of the petiole.
- Green leaf syndrome, which occurs in certain cultivars, marked by the persistence of the green color of the leaves followed by the bending of the petiole as in yellow leaf syndrome. Internally, the disease is characterized by vascular discoloration. This begins in the roots and rhizomes with a yellowing that proceeds to a red or brown color in the pseudostem.
These symptoms often get confused with the symptoms of bacterial wilt of banana, but there are ways to differentiate between the two diseases:
- Fusarium wilt proceeds from older to younger leaves, but bacterial wilt is the opposite.
- Fusarium wilt has no symptoms on the growing buds or suckers, no exudates visible within the plant, and no symptoms in the fruit. Bacterial wilt can be characterized by distorted or necrotic buds, bacterial ooze within the plant, and fruit rot and necrosis.
Once a banana plant is infected, it will continue to grow and any new leaves will be pale in color. Recovery is rare, but if it does occur any new emerging suckers will already be infected and can propagate disease if planted.
"Fusarium oxysporum f. sp. cubense" (Foc) is most prominent in banana and plantain, but some other similar relatives are also susceptible to infection. Different races of the disease are used to classify different major hosts affected by Foc. Race 1 was the initial outbreak which destroyed much of the world's Gros Michel bananas. Cavendish bananas are resistant to race 1, but tropical race 4 (or subtropical race 4) is the classification for Foc which affects Cavendish. Race 2 affects a cooking and dessert banana, Bluggoe.
Sooty blotch and flyspeck (SBFS) or apple summer disease is a plant disease caused by a complex of saprophytic fungi which colonize the epicuticular wax layer of apple ("Malus" x "domestica" Borkh.). It is found worldwide in regions with moist growing seasons.
Shot hole disease (also called Coryneum blight) is a serious fungal disease that creates BB-sized holes in leaves, rough areas on fruit, and concentric lesions on branches. The pathogen that causes shot hole disease is "Wilsonomyces carpophilus".
The amount of initial inoculum will be reduced when a crop other than corn is planted for ≥2 years in that given area; meanwhile proper tillage methods are carried out. Clean plowing and 1-year crop rotation in the absence of corn allows for greater reductions of the disease as well. Note that conventional tilling can reduce disease but can lead to greater soil erosion.
The blotches are cosmetic damage "unacceptable to consumers" and downgrade fruit from premium fresh-market grade to processing use, i.e. reduce its market value, but leaf and fruit development are not affected.
"F. oxysporum" is a major wilt pathogen of many economically important crop plants. It is a soil-borne pathogen, which can live in the soil for long periods of time, so rotational cropping is not a useful control method. It can also spread through infected dead plant material, so cleaning up at the end of the season is important.
One control method is to improve soil conditions because "F. oxysporum" spreads faster through soils that have high moisture and bad drainage. Other control methods include planting resistant varieties, removing infected plant tissue to prevent overwintering of the disease, using soil and systemic fungicides to eradicate the disease from the soil, flood fallowing, and using clean seeds each year. Applying fungicides depends on the field environment. It is difficult to find a biological control method because research in a greenhouse can have different effects than testing in the field. The best control method found for "F. oxysporum" is planting resistant varieties, although not all have been bred for every forma specialis.
"F. oxysporum" f. sp. "batatas" can be controlled by using clean seed, cleaning up infected leaf and plant material and breeding for resistance. Fungicides can also be used, but are not as effective as the other two because of field conditions during application. Fungicides can be used effectively by dip treating propagation material.
Different races of "F. oxysporum" f. sp. "cubense", Panama disease on banana, can be susceptible, resistant and partially resistant. It can be controlled by breeding for resistance and through eradication and quarantine of the pathogen by improving soil conditions and using clean plant material. Biological control can work using antagonists. Systemic and soil fungicides can also be used.
The main control method for "F. oxysporum" f. sp. "lycopersici", vascular wilt on tomato, is resistance. Other effective control methods are fumigating the infected soil and raising the soil pH to 6.5-7.
The most effective way to control "F. oxysporum" f. sp. "melonis" is to graft a susceptible variety of melon to a resistant root-stock. Resistant cultivars, liming the soil to change soil pH to 6-7, and reducing soil nitrogen levels also help control "F. oxysporum" f. sp. "melonis".
The fungus "Trichoderma viride" is a proven biocontrol agent to control this disease in an environment friendly way.
This disease is mainly found in tropical climates in Southern Asia, however some scattering exists:
"W. carpophilus" can remain viable for several months and spores are often airborne. Since the fungi thrive in wet conditions, overhead watering should be avoided. Remove and dispose of any infected buds, leaves, fruit and twigs. In fall, fixed copper or Bordeaux mixture can be applied.
Columnaris (also referred to as cottonmouth) is a symptom of disease in fish which results from an infection caused by the Gram-negative, aerobic, rod-shaped bacterium "Flavobacterium columnare". It was previously known as "Bacillus columnaris, Chondrococcus columnaris, Cytophaga columnaris" and "Flexibacter columnaris". The bacteria are ubiquitous in fresh water, and cultured fish reared in ponds or raceways are the primary concern – with disease most prevalent in air temperatures above 12–14 °C. It is often mistaken for a fungal infection. The disease is highly contagious and the outcome is often fatal. It is not zoonotic.
The bacteria usually enter fish through gills, mouth, or small wounds, and is prevalent where high s exist, or where conditions may be stressful due to overcrowding or low dissolved oxygen levels in the water column. The bacteria can persist in water for up to 32 days when the hardness is 50 ppm or more. Minerals are however essential for fish and often the reduction or removal of such minerals in treatment for Columnaris would affect fish mineral uptake and thus affect: oxygen utilization, osmotic regulation, metabolic processes, among may other biological processes and poor minerals (GH) may be a contributing cause to the advancement in severity of this disease, as deficits can increase vulnerability to opportunistic infections (citations).
Kashin–Beck disease occurrence is limited to 13 provinces and two autonomous regions of China. It has also been reported in Siberia and North Korea, but incidence in these regions is reported to have decreased with socio-economic development. In China, KBD is estimated to affect some 2 million to 3 million people across China, and 30 million are living in endemic areas. Life expectancy in KBD regions has been reported to be significantly decreased in relation to selenium deficiency and Keshan disease (endemic juvenile dilative cardiomyopathia).
The prevalence of KBD in Tibet varies strongly according to valleys and villages.
Prevalence of clinical symptoms suggestive of KBD reaches 100% in 5- to 15-year-old children in at least one village. Prevalence rates of over 50% are not uncommon. A clinical prevalence survey carried out in Lhasa prefecture yielded a figure of 11.4% for a study population of approximately 50,000 inhabitants. As in other regions of China, farmers are by far the most affected population group.