Fungi Uses in Pest Management
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Revision as of 12:39, 13 March 2013
This is a background of fungi uses in pest management. Testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing, testing...
Contents |
History
The use of Entomopathogenic fungi in pest management covers a wide variety of Eumycota subdivisions. These subdivisions of Eumycota include; Mastigomycotina, Zygomycotina, Ascomycotina, and Deuteromycotina [1] In 1981, the first mycoinsectiside registered in the U.S. was Hirsutella thompsonii and was given the registered name; Mycar. This species has been noted to cause epizootics as early as 1920 in some species of spider mites [2]
With the rising cost of synthetic chemical pesticides and increasing cases of pesticide resistance, the search for natural biologically based forms of pest management has been a key area of research for the last decade. With the world population rising over 7 billion and the drastic effects of climate change, the need for alternative forms of pest control will become essential. Although insects are key in the performance of many ecosystems, they play a large role in the 35 billion dollars worth of crop that is lost in the United States each year [3]
Biopesticides in Agriculture
Insect and weed management in important crops... sustainable agriculture, as a replacement for
Fungi used as a Herbicide
Fungi used as an Insecticide
Fungi used as a Fungicide
Biopesticides in Urban Environments
Entomopathogens are key components for integrated pest management solutions [4]. There is a large market for urban pest control that has been dominated by the use of pesticides and insecticides [4]. These chemical pesticides pose a danger not only to the person applying them, but other people, or pets, which may come into contact with the chemicals in an urban environment [4]. Previously used in agricultural settings as deterrents, fungi such as Beauveria bassiana,Metarhizium anisopliae and Paecilomyces fumosoroseus may have possible pest control applications in urban settings as well [5].
Treatment of pest insects with fungi relies on the natural spread of the disease organism, whether through direct contact with nest mates, or ingestion [4]. Biopesticides have the largest potential for treatment of social insects such as cockroaches, ants and termites [4]. Application methods include the use of bait stations or direct application to a located nest [4]. In order to be effective, pathogenic conidia must come into contact with the insect cuticle, or exoskeleton [4].
Pathogenic fungi may have a greater repellant effect, and can be applied to plants or mixed with soil, or even mixed with paint and painted onto timber [4]. These fungus treatments may reduce the infestation by deterring pests rather than eliminating them [4]. Studies indicated similar success with fungal spores to those effects achieved by bifenthrin and triflumeron insecticides [4].
Overcoming this repellency can be achieved by mixing the conidia with agar or cellulose, diluting the conidia and masking the factors inducing repellency [4]. Additionally, adding the repellent spores to an attractant such as honey water may entice the insects to visit the biopesticide trap [4].
Cockroaches
Cockroaches are not just a nuisance pest; they are also capable of transmitting a variety of human pathogens and diseases, which makes them a public health concern [4]. Cockroach infestations are notoriously hard to treat with baited pesticide traps, as they are able to detect and avoid both chemical and microbial pesticides [4]. Research in the field of cockroach infestation control through the use of biopesticides, specifically fungi, is extremely limited. However, it has been determined that Cordyceps blattae is highly pathogenic for the German cockroach (Blattella germanica) [4]. Unfortunately, dead cockroaches infected with fungi are not cannibalized, which suggests avoidance by the healthy cockroaches [4].
Ants
Black or brown ants are those which may invade houses, causing no structural or other types of damage, but annoy homeowners [4]. Ants that live inside structures may also include Carpenter ants that can damage the structural integrity of buildings [4]. Ants which are a problem in urban landscapes, such as fire ants (Solenopsis xyloni) may attack humans or domestic animals, damage landscape plants or other materials outside human structures [4]. B. bassiana conidia have been effectively used to control the southern fire ant and reduce their populations in urban environments [4]. Mycelium stage of M. anisopliae (pre-sporulation) is readily taken back to the nest by black and brown ants, where it will later produce spores [5].
Termites
Termites are social insects living in colonies comprising of a king and queen together with numerous workers and soldiers. Their life cycle is hemimetabolous with the queen laying eggs that hatch into larvae that can develop into workers, soldiers or new reproductives [5]. It is necessary to deposit large quantities of M. anisopliae conidia within the central portion of the nest to infect and kill the entire termite colony [6]. Control of colonies of pest species of termite can be achieved within 3 months with a single treatment between 1-10g of conidia applied directly to the nest, and spores will remain active in nests for at least 2 years [5].
With application of fungi as a biopesticide, termite workers may be found in the nest for many weeks after most of the colony has been killed. There is a possibility that the colony can produce neotenic reproductives and can recover despite the loss of the royal pair [4]. The use of fungi for elimination of a termite colony may not be effective, but perhaps the greatest potential for application of biological control to suppression of termite populations is the use of pathogenic microorganisms or conidia as deterrents to protect timber [5] [6].
Problems
Though the potential for control is greatest in the social insects, there are a number of behavioural traits of ants and termites that limit the effectiveness of fungi as pest control. These behaviours include nest hygiene, self-grooming and allogrooming, and isolation of affected individuals; all of which can either remove or spread entomopathogens [4]. Similarly, due to the low genetic diversity between individuals in social insect nests, effectiveness of pathogens can be either compromised or enhanced [4]. For these reasons, the objective of control tactics must be the elimination of the reproductive potential of the nest [4].
Development
Entomopathogens formulated as biopesticides have to be mass produced and applied in large amounts [4]. Strains selected have to be virulent, be able to tolerate temperatures above 30C, pose no health threats to humans and higher animals, and have long-lived and robust spores [5]. Additionally, quality control, shelf life and field longevity of biological agents as pest control must be assessed in order for biopesticides to become marketable [5].
Since pathogens normally have little or no mobility on their own, a mobile or readily distributed and possibly self-perpetuating control agent should mean more complete and less labor intensive pest control [6]. Entomopathogens are naturally slow-acting and therefore ideal for use in bait stations, where the forager is not immediately killed [4]. This allows the active ingredient to be transferred to nest mates, juveniles and reproductives in the nest [5]. B. bassiana shows the highest potential for control of several urban pests [5]. Powders and granular baits are recommended for application directly onto the nest, if it can be located [5]. If the nest cannot be located, it is recommended to use bait stations that contain pathogenic fungal conidia mixed with an attractant, such that the foragers return to the nest with the pathogen [6].
Integrated pest control measures are needed whereby the pathogen provides short-term cessation of damage while changes are made to the environment to make the building less attractive to pests. Alternatively pathogens could be used in baits over a long period of time to eliminate the colony [4]. However, both the insect and the environments in which they live can significantly limit the success of fungal pathogens [5].
Pro et Contra
Novel Uses of Fungi as Biopesticides
Species
Definitions
Epizootic- A type of disease that appears in an animal population as a newly recorded case. It may also spread much faster than what was previously expected.
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