| Corynespora cassiicola | |
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| Species: | C. cassiicola |
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| Corynespora cassiicola (Berk. & M.A. Curtis) C.T. Wei, (1950) | |
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Cercospora melonisCooke, Gard. Chron., (1896) Contents | |
Corynespora cassiicola is a species of fungus well known as a plant pathogen. It is a sac fungus in the family Corynesporascaceae. It is the type species of the genus Corynespora . [1]
This fungus infects over 530 species of plants [1] in 53 families. [2] In the tropics and subtropics, it is most common. [1] It has also been isolated from nematodes and from human skin. [1]
The fungus is known as a pathogen of many agricultural crop plants, especially cowpea, cucumber, papaya, rubber, soybean, and tomato. It has caused crop failures resulting in high economic losses in over 70 countries, [1] including losses of over US$3000 per acre in tomato crops in Florida in the United States. [2] On several plants, such as tomatoes, the fungus causes a disease called target spot [3] or target leaf spot. [2] The disease is identified by leaf damage taking the form of target-shaped spots with light centres and dark margins, as well as pits on the fruit. [3] The fungus also causes a disease on the cultivated rubber tree Hevea brasiliensis called corynespora leaf fall (CLF). [4] It is one of the most economically significant fungal pathogens of rubber trees in Asia and Africa, causing "fishbone"- or "railway track"-shaped lesions on the leaves. [5]
In regards to detection of Corynespora cassiicola, it is useful to inspect the plant's bottom leaves while looking for ring-patterned spots that can be up to 10 mm in diameter. [6] This pathogen is able to show symptoms on a vast host range and on several different structures. That being said, it is beneficial to additionally check the plant's roots, stems, and fruit exterior for symptoms.
There are several cultural control practices that may be useful for managing this pathogen. Before planting begins, measures should be taken for prevention. These measures include avoiding planting crops next to ones known to already have the disease. In order to do so, seedlings should be checked for these leaf spots previously mentioned. If the Corynespora cassiicola is discovered on the plant during its development, management of the disease includes removing and burning the plant's lower leaves. Additionally, it's important to ensure that there are no weeds present on the plant plots because these weeds may act as hosts and harbor the fungus. [7] Additionally, weeds can be considered disadvantageous in a field because they work to compete against the host for nutrients. Some tactics for managing weeds include applying mulch to the soil or introducing a natural pathogen of the weed as a method of biocontrol. If the pathogen is discovered after harvesting the host, management includes burning the infected crop in the attempt to rid the disease from the environment. Furthermore, practicing plant rotation and waiting three years before replanting the host on the same land can be beneficial for pathogen prevention. [7]
Chemical control may also be employed to promote disease prevention. Several researchers at the University of Florida conducted a study in which they tested a variety of fungicides on the pathogen. They tested 11 Corynespora cassiicola isolates and concluded that all tested isolates were highly resistant to the fungicides azoxystrobin and pyraclostrobin. [8] This information suggests that because QoIs are not advantageous fungicides to use for Corynespora cassiicola management, fungicides with different FRAC codes may be more useful. So, farmers should consider fungicides with modes of action that are different from QoI when determining which chemical to apply.
Although Corynespora cassiicola has been reportedly located in a wide distribution throughout the world, the conditions in which this pathogen best spreads and develops are found in the tropics and subtropics. [9] The locations of these reports include plant species in American Samoa, Brazil, Malaysia, and Micronesia. [10] Furthermore, the pathogen was reported in Mexico in 2013 [11] and China in 2014. [12]
Corynespora cassiicola requires high humidity for infection and is additionally favored in locations with substantial periods of high moisture (16–44 hours). In other words, the leaf wetness is likely a major environmental factor driving the disease for this fungal pathogen. The humidity may be used as a surrogate for leaf wetness, as it is an essential component of an environment and has data that can be easily measured. This pathogen is an especially prominent foliar disease of tomato in Florida, which provides the optimal high humidity environment for the disease growth and development. Images of the symptoms in this opportune environment have been provided by professors of plant pathology from Florida, Dr. Ken Pernezny and Dr. Gary Vallad. In regards to the symptoms on the leaves of tomato plants, there is evidence of chlorosis as well as small, brown circular spots covering the leaves. The symptoms of the tomato fruit exterior include larger, brown circular deformations on the plant's exterior skin. These illustrations are important to note because they depict the symptoms of Corynespora cassiicola on a tomato plant that is developing in its favorable environment.
Additionally, this pathogen may be easily dispersed throughout the environment by wind. Thus, it has been found on diverse substrates of its hosts including the roots, stems, and leaves. The pathogen has even been reported on human skin, seen as causing severe damage and blisters. [13]
Corynespora cassiicola is an important pathogen because it's responsible for a considerable loss of crop production and yield. This pathogen's first notorious epidemic involved the Hevea brasilienis host, also known as the Pará Rubber Tree. Approximately 4,600 hectare of this species have been destroyed in Sri Lanka since this first epidemic in 1987. [13] Therefore, this pathogen reduces the yield of natural rubber latex in Asian and African countries especially and is thus a major threat to millions of rubber farmers. [9]
There have been 72 documented reports of Corynespora cassiicola from 1957 until 2013. [13] This suggests an increase in both awareness and aggressiveness for this pathogen. Moreover, Corynespora cassiicola has become a prominent disease in both in cucumbers and tomatoes. [13] The photograph by Dr. Ken Pernezny illustrates the foliar damage of Corynespora cassiicola and the reduced yield of tomato plants in a Florida field. Thus, this pathogen has the ability to inflict major economic loss. Furthermore, Corynespora cassiicola's host range includes 530 species from 380 genera. [13] This broad host range adds danger in the fact that this economic loss does not just apply to one specific crop. Rather, a farmer working in a field where this fungi has the opportunity to grow must care for a variety of hosts. Additionally, this reinforces the importance of gaining knowledge to better understand this pathogen and prevent it from developing.
The fungus has been the subject of genetic analysis, which revealed that it has a high genetic diversity. Results of this variation within the species include its ability to adapt to many hosts and many environments, and its ability to cause different kinds of disease states in its host plants. [1] Several isolates of the fungus have recently proven to be resistant to the fungicide benzimidazole, making the fungus harder to treat in crops. [14]
Because it also infects many plants that are considered noxious weeds, the fungus has been proposed for use as a bioherbicide and an agent of biological pest control. [1]
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as the signs of the causal pathogen are quite distinctive. Infected plants display white powdery spots on the leaves and stems. This mycelial layer may quickly spread to cover all of the leaves. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.
Black sigatoka is a leaf-spot disease of banana plants caused by the ascomycete fungus Mycosphaerella fijiensis (Morelet), also known as black leaf streak. It was discovered in 1963 and named for its similarities with yellow Sigatoka, which is caused by Mycosphaerella musicola (Mulder), which was itself named after the Sigatoka Valley in Fiji. In the same valley an outbreak of this disease reached epidemic proportions from 1912 to 1923.
Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. This disease has been investigated extensively since the early years of this century. The pathogen that causes Fusarium wilt is Fusarium oxysporum. The species is further divided into formae speciales based on host plant.
Soybean rust is a disease that affects soybeans and other legumes. It is caused by two types of fungi, Phakopsora pachyrhizi, commonly known as Asian soybean rust, and Phakopsora meibomiae, commonly known as New World soybean rust. P. meibomiae is the weaker pathogen of the two and generally does not cause widespread problems. The disease has been reported across Asia, Australia, Africa, South America and the United States.
A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions often have a centre of necrosis. Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves.
Alternaria alternata is a fungus causing leaf spots, rots, and blights on many plant parts, and other diseases. It is an opportunistic pathogen on over 380 host species of plant.
Colletotrichum acutatum is a plant pathogen and endophyte. It is the organism that causes the most destructive fungal disease, anthracnose, of lupin species worldwide. It also causes the disease postbloom fruit drop on many varieties of citrus, especially Valencia and navel oranges in Florida.
Pseudocercosporella capsellae is a plant pathogen infecting crucifers. P. capsellae is the causal pathogen of white leaf spot disease, which is an economically significant disease in global agriculture. P. capsellae has a significant effect on crop yields on agricultural products, such as canola seed and rapeseed. Researchers are working hard to find effective methods of controlling this plant pathogen, using cultural control, genetic resistance, and chemical control practices. Due to its rapidly changing genome, P. capsellae is a rapidly emerging plant pathogen that is beginning to spread globally and affect farmers around the world.
Verticillium dahliae is a fungal plant pathogen. It causes verticillium wilt in many plant species, causing leaves to curl and discolor. It may cause death in some plants. Over 400 plant species are affected by Verticillium complex.
Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early", foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides. Early blight can also be caused by Alternaria tomatophila, which is more virulent on stems and leaves of tomato plants than Alternaria solani.
Phytophthora capsici is an oomycete plant pathogen that causes blight and fruit rot of peppers and other important commercial crops. It was first described by L. Leonian at the New Mexico State University Agricultural Experiment Station in Las Cruces in 1922 on a crop of chili peppers. In 1967, a study by M. M. Satour and E. E. Butler found 45 species of cultivated plants and weeds susceptible to P. capsici In Greek, Phytophthora capsici means "plant destroyer of capsicums". P. capsici has a wide range of hosts including members of the families Solanaceae and Cucurbitaceae as well as Fabaceae.
Ascochyta pisi is a fungal plant pathogen that causes ascochyta blight on pea, causing lesions of stems, leaves, and pods. These same symptoms can also be caused by Ascochyta pinodes, and the two fungi are not easily distinguishable.
Didymella bryoniae, syn. Mycosphaerella melonis, is an ascomycete fungal plant pathogen that causes gummy stem blight on the family Cucurbitaceae, which includes cantaloupe, cucumber, muskmelon and watermelon plants. The anamorph/asexual stage for this fungus is called Phoma cucurbitacearum. When this pathogen infects the fruit of cucurbits it is called black rot.
Cercospora sojina is a fungal plant pathogen which causes frogeye leaf spot of soybeans. Frog eye leaf spot is a major disease on soybeans in the southern U.S. and has recently started to expand into the northern U.S. where soybeans are grown. The disease is also found in other soybean production areas of the world.
Cercospora melongenae is a fungal plant pathogen that causes leaf spot on eggplant. It is a deuteromycete fungus that is primarily confined to eggplant species. Some other host species are Solanum aethiopicum and Solanum incanum. This plant pathogen only attacks leaves of eggplants and not the fruit. It is fairly common among the fungi that infect community gardens and home gardens of eggplant. Generally speaking, Cercospora melongenae attacks all local varieties of eggplants, but is most severe on the Philippine eggplant and less parasitic on a Siamese variety.
Puccinia thaliae is the causal agent of canna rust, a fungal disease of Canna. Symptoms include yellow to tan spots on the plant's leaves and stems. Initial disease symptoms will result in scattered sori, eventually covering the entirety of the leaf with coalescing postulates. Both leaf surfaces, although more predominant on the underside (abaxial) of the leaf, will show yellow to brownish spore-producing these pustulate structures, and these are the signs of the disease. Spots on the upper leaf-surface coalesce and turn to brown-to-black as the disease progresses. Infection spots will become necrotic with time, with small holes developing in older leaves. These infected leaves eventually become dry and prematurely fall.
This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United States.
Grey leaf spot (GLS) is a foliar fungal disease that affects maize, also known as corn. GLS is considered one of the most significant yield-limiting diseases of corn worldwide. There are two fungal pathogens that cause GLS: Cercospora zeae-maydis and Cercospora zeina. Symptoms seen on corn include leaf lesions, discoloration (chlorosis), and foliar blight. Distinct symptoms of GLS are rectangular, brown to gray necrotic lesions that run parallel to the leaf, spanning the spaces between the secondary leaf veins. The fungus survives in the debris of topsoil and infects healthy crops 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 of Cercospora zeae-maydis is assumed to be Mycosphaerella sp.
Alternaria black spot of canola or grey leaf spot is an ascomycete fungal disease caused by a group of pathogens including: Alternaria brassicae, A. alternata and A. raphani. This pathogen is characterized by dark, sunken lesions of various size on all parts of the plant, including the leaves, stem, and pods. Its primary economic host is canola. In its early stages it only affects the plants slightly by reducing photosynthesis, however as the plant matures it can cause damage to the seeds and more, reducing oil yield as well.
Alternaria leaf spot or Alternaria leaf blight are a group of fungal diseases in plants, that have a variety of hosts. The diseases infects common garden plants, such as cabbage, and are caused by several closely related species of fungi. Some of these fungal species target specific plants, while others have been known to target plant families. One commercially relevant plant genus that can be affected by Alternaria Leaf Spot is Brassica, as the cosmetic issues caused by symptomatic lesions can lead to rejection of crops by distributors and buyers. When certain crops such as cauliflower and broccoli are infected, the heads deteriorate and there is a complete loss of marketability. Secondary soft-rotting organisms can infect stored cabbage that has been affected by Alternaria Leaf Spot by entering through symptomatic lesions. Alternaria Leaf Spot diseases that affect Brassica species are caused by the pathogens Alternaria brassicae and Alternaria brassicicola.