''Colletotrichum acutatum'' is a

plant pathogen Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...

and

endophyte An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; ...

. It is the organism that causes the most destructive fungal disease,

anthracnose A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...

, of

lupin ''Lupinus'', commonly known as lupin, lupine, or regionally bluebonnet, is a genus of plants in the legume family Fabaceae. The genus includes over 199 species, with centres of diversity in North and South America. Smaller centres occur in No ...

species worldwide. It also causes the disease postbloom fruit drop on many varieties of

citrus ''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. ''Citrus'' is nativ ...

, especially Valencia and navel oranges in

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

.N.A. Peres and M.M. Dewdney, (2016). 2016 Florida Citrus Pest Management Guide: Ch. 22 "Postbloom Fruit Drop" Publication #PP-45, University of Florida IFAS Extension.

Host and symptoms

''Colletotrichum acutatum'' has a broad host range, but is most important in strawberries. The pathogen causes black spot of fruit, but can also be seen attacking the plant at its crowns, roots and leaves. After planting, stunting and yellowing as well as wilting may occur. General symptoms of the disease in other plants can also be seen on flowers, petioles, and roots. Stems are also a prominent place to see symptoms. Lesions on the stem can appear dark colored, oval shaped, and possibly have immersed spots located on petioles and runners. Once ''C.acutatum'' infects these parts of the plant, it can cause other diseases to unfold such as crown root rot, defoliation, bloom blight and fruit rot. Unfortunately, the most significant loss can be seen once the fruit is attacked. If the fruit is infected it will develop small brown spots (green fruit) or black spots (red fruit) and can expand throughout the fruits' surface.

Environment

This pathogen has a wide geographical distribution. Strains of the pathogen are present throughout various climates worldwide. Temperature can affect how symptoms appear on the host. Optimal temperature for growth of ''C. acutatum'' is 25 degrees Celsius. For instance, in weather with high humidity, orange colored spores appear on the hosts' lesions. Specifically in strawberries, this disease appears to be more harmful in warm climates. Transference of disease occurs when conidia are spread by water, specifically rain or irrigation water. Another way of contamination is from infected equipment or wind.

Taxonomic history

Historically fungi that were pathogenic on different plants were often given different names, even though they often had near identical morphology. In 195
Josef Adolf von Arx
synonymized about 600 fungal species names as ''

Colletotrichum gloeosporioides ''Glomerella cingulata'' is a fungal plant pathogen, being the name of the sexual stage ( teleomorph) while the more commonly referred to asexual stage ( anamorph) is called ''Colletotrichum gloeosporioides''. For most of this article the pathog ...

''. In 1965 ''C. gloeosporioides'' strains that had acute conidia and slower growth were renamed as ''Colletotrichum acutatum''. With the invention of easy and affordable

DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, thymine, cytosine, and guanine. The ...

technologies, species identification switched from being based on morphology to being based on a combination of

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

and

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

. In 2012 the ''C. acutatum'' species was split up into more than two dozen new species, and is now referred to as the ''C. acutatum''

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

. The ''C. acutatum'' species complex still includes a species called ''C. acutatum,'' but it is now defined more narrowly than it had been from 1965 to 2012.

As a Biocontrol Agent

This fungus attacks the Australian species '' Hakea sericea'' in South Africa, where this shrub is an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

. For this reason, local researchers have been investigating the application of this fungus as a means of

biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...

Pest Management

Cultural control

Sanitation is critical in controlling the disease. Thoroughly washing plants by removing all the dirt could reduce occurrence. This method has also been demonstrated to reduce pests such has anthracnose. Proper sanitation of equipment could reduce exposure of contracting the pathogen. This would be equipment used in transportation, packing, storage, etc. Crop rotation, as well as the removal of weeds is also helpful in reducing the pathogen in the soil. Removing weeds from the field is a critical step; the pathogen on the dead weeds could still produce spores.

Chemical control

A common method of control for this disease is the use of fungicides. Fungicides are soil fumigants that are used to decrease amount of inoculum in the soil.

Chloropicrin Chloropicrin, also known as PS (from Port Sunlight) and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. It was used as a poison gas in World War I and the ...

, a fungicide, has seen good results with regular application. Unfortunately, relying on just one fungicide heavily can increase the disease's tolerance. Moreover, the timing of the application is very crucial. With poorly timed applications, there could be an increase of disease severity due to the disturbance of natural biocontrol mechanisms and increased crop susceptibility. Pest control is also crucial in the containment of the disease. After rainfall or irrigation, anthracnose symptoms may occur. Using foliar fungicide can help prevent spread of the disease and minimize anthracnose.

References

acutatum Fungal plant pathogens and diseases Fungal citrus diseases Fungi described in 1965 Fungus species {{fungus-fruit-disease-stub