Fungi Uses in Pest Management
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| <p>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 <ref name="Milner and Pereira"/>. 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 <ref name="Lenz"/> <ref name="Grace"/>.</p> | <p>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 <ref name="Milner and Pereira"/>. 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 <ref name="Lenz"/> <ref name="Grace"/>.</p> | ||
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Revision as of 14:08, 19 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
Introduction
The presence of weeds can result in the loss of up to half of a grower’s expected crop yield. The lost yield results in economic losses which is a problem in the agriculture industry. Fungi can be used as a herbicide to gain control of weeds and solve this issue. Fungal herbicides have been legal in Canada since 1973[4]. In order to use a fungi for this purpose, a mycoherbicide is created with the fungi as its active ingredient. This mycoherbicide must be able to inhibit weed growth without harming the crop or the living things surrounding it. A benefit is that the fungi used are host specific and will reside on the soil or weed host, while a commercial chemical herbicide would need to be reapplied to the crop. Certain mycoherbicides work better on certain strains of weeds. There are currently 37 mycoherbicides and 8 techniques of applying them [5]. The fungi species most commonly used as herbicides in North America are Collectrichum gloeosporioides (Collego®) and Phytophthora palmivoraa (De Vine®).
Process
Mycoherbicides act by releasing phytopathogens to suppress weed growth. The phytopathogens release phytotoxins that can kill weeds in up to five weeks time. The pathogens released have the ability to produce spores for asexual reproduction and are tested to be stable and temperature tolerant. Fungal herbicides are easily made once the anti-herb properties have been testing as well as the living conditions for that fungi. They are easily applied by spraying. Once applied, the spores will germinate and penetrate the herb tissue and the phytotoxins will start to work. However, there are reasons fungal herbicides may not be used in place of a harmful chemical. In North America, fungal herbicides have to be registered and approved by the Environmental Protection Agency (EPA) which can take years. The anti-herb capacity of fungi is generally less than that of a chemical herbicide. Fungal herbicides are not commonly used because their success rate depends on the environmental conditions and because they are so host specific.
Phytotoxins
Phytotoxins are low molecular weight secondary metabolites that cause plant disease. In this case, the plant being infected is a weed plant. Phytotoxins may also be responsible for visual symptoms of disease such as wilting or necrosis. A common phytotoxin found in the fungi species Penicillium is vulculic acid. Vulculic acid works against weeds by increasing leaf membrane permeability, inducing lipid peroxidation and damaging the cell membrane. Phytotoxins have a limited stable state because of their short half-life and sensitivity to the environment. Phytotoxins are difficult to produce for commercial sale because they are produced in very small quantities by fungi and difficult to isolate.
Arrowhead
A specific weed strain commonly known as arrowhead (Sagitaria trifolia) is the cause of the largest rice plantation problem in Iran. Arrowhead is notably resistant to chemical herbicides. Collego® is used in the USA as the solution to arrowhead. The fungi Alternaria pellucida was tested and proved that it could successfully be used as a mycoherbicide against arrowhead in Iran. This fungi works by preventing early growth of the weed. The fungi species was tested for its anti-herb properties on three indigenous cultivars of rice, two bred cultivars and lastly on an arrowhead infested cultivar, all cultivated separately in a greenhouse. Alternaria pellucida significantly altered the height of the arrowhead weed and was concluded to be a mycoherbicide able to control the arrowhead weed.
(Not done, don't worry -Emily)
Fungi used as an Insecticide
Fungi used as a Fungicide
Biopesticides in Urban Environments
Entomopathogens are key components for integrated pest management solutions [6]. There is a large market for urban pest control that has been dominated by the use of pesticides and insecticides [6]. 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 [6]. 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 [7].
Treatment of pest insects with fungi relies on the natural spread of the disease organism, whether through direct contact with nest mates, or ingestion [6]. Biopesticides have the largest potential for treatment of social insects such as cockroaches, ants and termites [6]. Application methods include the use of bait stations or direct application to a located nest [6]. In order to be effective, pathogenic conidia must come into contact with the insect cuticle, or exoskeleton [6].
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 [6]. These fungus treatments may reduce the infestation by deterring pests rather than eliminating them [6]. Studies indicated similar success with fungal spores to those effects achieved by bifenthrin and triflumeron insecticides [6].
Overcoming this repellency can be achieved by mixing the conidia with agar or cellulose, diluting the conidia and masking the factors inducing repellency [6]. Additionally, adding the repellent spores to an attractant such as honey water may entice the insects to visit the biopesticide trap [6].
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 [6]. Cockroach infestations are notoriously hard to treat with baited pesticide traps, as they are able to detect and avoid both chemical and microbial pesticides [6]. 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) [6]. Unfortunately, dead cockroaches infected with fungi are not cannibalized, which suggests avoidance by the healthy cockroaches [6].
Black or brown ants are those which may invade houses, causing no structural or other types of damage, but annoy homeowners [6]. Ants that live inside structures may also include Carpenter ants that can damage the structural integrity of buildings [6]. 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 [6]. B. bassiana conidia have been effectively used to control the southern fire ant and reduce their populations in urban environments [6]. 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 [7].
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 [7]. 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 [8]. 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 [7].
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 [6]. 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 [7] [8].
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 [6]. Similarly, due to the low genetic diversity between individuals in social insect nests, effectiveness of pathogens can be either compromised or enhanced [6]. For these reasons, the objective of control tactics must be the elimination of the reproductive potential of the nest [6].
Development
Entomopathogens formulated as biopesticides have to be mass produced and applied in large amounts [6]. 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 [7]. Additionally, quality control, shelf life and field longevity of biological agents as pest control must be assessed in order for biopesticides to become marketable [7].
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 [8]. Entomopathogens are naturally slow-acting and therefore ideal for use in bait stations, where the forager is not immediately killed [6]. This allows the active ingredient to be transferred to nest mates, juveniles and reproductives in the nest [7]. B. bassiana shows the highest potential for control of several urban pests [7]. Powders and granular baits are recommended for application directly onto the nest, if it can be located [7]. 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 [8].
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 [6]. However, both the insect and the environments in which they live can significantly limit the success of fungal pathogens [7].
Pro et Contra
Novel Uses of Fungi as Biopesticides
Species
Definitions
Notes and References
- ↑ BIOLOGICAL and BIOTECHNILOGICAL CONTROL of INSECT PESTS (2000). Rechcigl. E.J. and Rechcigl. N.A. (Pg 49) Pg
- ↑ Biological and Biotechnological Controls of INSECT PESTS Rechcigl E.J., Rechcigl N.A. Pg 49-51.
- ↑ Entomopathogenic fungi as biological control agents. P. A. Shah, J. K. Pell. Applied Microbiology and Biotechnology June 2003, Volume 61, Issue 5-6, pp 413-423.
- ↑ Misra, H.P. Weed Management Through Fungal Herbicides. November 2005. Orissa Review. http://orissa.gov.in/e-magazine/Orissareview/nov2005/engpdf/Weed_Management_Through_Fungal_Herbicides.pdf
- ↑ Misra, H.P. Weed Management Through Fungal Herbicides. November 2005. Orissa Review. http://orissa.gov.in/e-magazine/Orissareview/nov2005/engpdf/Weed_Management_Through_Fungal_Herbicides.pdf
- ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 6.18 6.19 6.20 6.21 6.22 6.23 6.24 6.25 6.26 Milner, RJ. and Pereira RM. 2007. Microbial control of urban pests - cockroaches, ants and termites. Field Manual of Techniques in Invertebrate Pathology. 20(2):695-711
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 Lenz, M. 2005. Biological control in termite management: the potential of nematodes and fungal pathogens. Proceedings of the Fifth International Conference on Urban Pests. 47-52
- ↑ 8.0 8.1 8.2 8.3 Grace, JK. 1997. Biological control strategies for suppression of Termites. J. Agric. Entomol. 14(3):281-289
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