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Fungi Uses in Pest Management

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Lecanicillium lecanii on hemlock woolly adelgid cadaver
Lecanicillium lecanii on hemlock woolly adelgid cadaver[1]
Beauveria bassiana on pecan weevil (Curculio caryae)
Beauveria bassiana on pecan weevil (Curculio caryae)[2]
Trichoderma spp. on Norway spruce (Picea abies)
Trichoderma spp. on Norway spruce (Picea abies)[3]

Fungi are useful biological controls for pests in crops and urban environments and have been commercially available since 1981.[4] They can be used as herbicides, insecticides and fungicides. Mycopesticides are interesting organic alternatives to chemical pesticides due to their enhanced safety and their high specificity for the non-targeted species such as humans, pets and desired insects.[5] They share advantages and disadvantages with other biopesticides.[5] Lecanicillium lecanii, Beauveria bassiana and Trichoderma spp. are amongst the most commonly used species and have been widely studied in spite of the short history of this field of study. With the growing enthusiasm for organic commercial farming and justified environmental concerns in the population, mycopesticide have a definitely a bright future.[6]

Contents

[edit] History

For over 100 years, scientists have been studying many different species of fungi with entomopathogenic characteristics but the use of these organisms in the field has been relatively elusive. Many of these fungal organisms are not only entomopathogens, but also aid in general plant growth. Since the late 1940's, chemical insecticides have been the main tool that growers have utilized, in order to control potentially damaging pests and diseases. Some of the earliest recorded studies of entomopathogenic fungi occurred in the early 1800 when the silkworm industry in France was devastated by Beauveria bassiana. As a consequence of this insight, further research began looking into the use of fungal insect pathogens to manage a wide range of pests.[7]


Most recently, DNA sequence analysis has lead to a much better understanding between the differences in entomopathogenic fungi and other types of fungi. This new research has revealed that some of these entomopathogenic fungi also play the role of beneficial rhizosphere associates, plant growth promoters, as well as plant endophytes. These findings have now lead to further research to determine if some of these entomopathogenic fungi can be used for more than just one purpose.


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.[4] In 1981, the first mycoinsectiside registered in the U.S. was Hirsutella thompsonii and was given the registered name; Mycar.[8] This species has been noted to cause epizootics as early as 1920 in some species of spider mites.[4]

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 worth of crop that is lost in the United States each year.[9]


There is enormous potential for pest and vector control in pest management in the future due to an increasing amount of knowledge in the area of mycology.[10]

[edit] Types of Mycopesticides

[edit] Mycoherbicide

See main article: Fungi used as a Herbicide

Fungi can be used as an herbicide to exterminate specific weeds and other plants that are detrimental to the effective growth of crops. In order to use a fungus for this purpose, a mycoherbicide is created with the fungi as its active ingredient. The use of mycoherbicides focus on the theory of the disease triangle. The disease triangle breaks down the conditions that need to be apparent for infection to occur, those being the environment, pathogen and host. The following will fall under one or more of these categories. Mycoherbicides act by releasing phytopathogens to suppress weed growth. The phytopathogens release phytotoxins that can kill weeds in up to five weeks time. A common phytotoxin found in the fungi species Penicillium is vulculic acid.[11] The fungi species most commonly used as herbicides in North America are Collectrichum gloesporioides (Collego®) and Phytophthora palmivoraa (De Vine®).[11] 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.[12] Other types of fungi that can be used as mycoherbicides are rusts and mildews. These fungi use spore distribution to cause infection in their host plants.

[edit] Mycoinsecticide

See main article: Fungi used as a Insecticide

Certain species of fungi can act as parasites of insect. When a fungus is used as insecticides, it is called mycoinsecticide. [13] In recent years, crop protection has been trending towards integrated pest management (IPM) using bacteria and fungi as insecticides. Approximately 750 species of fungi are pathogenic to insects and only 12 are being utilized as insecticides.[13] Two prominent species of fungi used as insecticides are Beauveria bassiana, and Metarhizium anisopliae. Mycoinsecticides function by first being applied to the insects in spray form. The fungi then use their hyphae to burrow into the insects. The hyphae spread the insectotoxins throughout the insect to activate them, eventually leading to the insect’s death.

[edit] Mycofungicide

See main article: Fungi used as a Fungicide

There are many cases of mycoparasitism in nature. In fact, a large amount of dormant spores like sclerotia or chlamydospore are found in the wild already parasitized by another fungi.[14] This is made possible by the ability of most fungi to release lytic enzymes like chitinase that allows them to break down chitinuous cell walls. The parasitism of a fungi on another one occurs generally through four main stages: chemotaxi, recognition, attachment and penetration.[15]The type of relationship that will follow such an invasion will be either necrotrophic or biotrophic.[5] The most commonly used species are in the Trichoderma genus.[16]

[edit] Mycopesticides in Urban Environments

See main article: Fungi uses in Urban Environments

Entomopathogens are key components for integrated pest management solutions.[17] There is a large market for urban pest control that has been dominated by the use of pesticides and insecticides.[17] 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.[17] 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.[18]

[edit] Advantages and Disadvantages

See main article: Advantages and Disadvantages

The negative impacts of chemical pesticides is what has guided new attention towards increased emphasis on biological control agents with respect to using fungi through the use of naturally occurring pathogens of arthropods. Many of these naturally occurring pathogens produced by fungi are already being employed, mostly on a small scale controlling arthropod pests in greenhouse crops, orchards, ornamentals, turf and lawn grasses, stored products and forests, and also for moderation of vectors of animal and human diseases.[19]


Although the utilization of the full potential of fungal biocontrol agents against arthropod pests has had limited commercial success, the major advantages of these biocontrol agents are:[5]

  • Effectiveness and potentially high specificity;
  • Acceptable naturalness;
  • Safety for humans and other non target organisms;
  • Reduced chemical pesticide use and consequential reduction of residues in food and the environment;
  • Protection of natural enemies of the pest;
  • Protection of biodiversity in managed ecosystems.

Despite these promising advantages of using fungi as biological control agents in pest management, there are some disadvantages as well such as:[5]

  • Can be very costly to produce for commercial use and in quantity;
  • They can have a short shelf life;
  • The pest must be present before the pathogen can be usefully applied thus making preventative treatment difficult.

Furthermore, the disadvantages of the use of entomogenous fungi as biocontrol agents against arthropod pests has been lacking by the need for specific environmental conditions (humidity over 80% and above) during the prolonged period in which the fungi are required to have spores germinate and then penetrate the surface of the arthropods cuticle. This is different from bacterial pathogens in which they go through the host’s digestive tracts.[5] Researchers have been trying to overcome this problem through the development of oil based and other formulations of fungal spores for use in biological control. Thus we can see that a intricate set of interacting processes, both environmental and biotic, are necessary for or inhibitory to development of epizootics caused by entomopathogenic fungi. These include microbial antagonists; host behavior, physiological condition, pathogen vigor and age; presence of pesticides; and appropriate temperature, humidity, and inoculum thresholds.[19]

[edit] Novel Uses of Mycopesticides

Throughout history, there have been many instances of harmful pesticides being released into the environment without fully understanding the implications of such actions. One example of this was the use of DDT, a chemical that has an extremely long half-life and a high degree of bioaccumulation directly linked to a high lipophilicity, which causes eggshell thinning in several birds, including birds of prey [20]. With global environmental awareness increasing, there has been a greater demand for less harmful pesticides. Alternatives to pesticides, biopesticides, generally have a lower toxicity, increased safety, as well as a high efficacy in pest control [21].

Consequently, the demand and commercial application of microbial biopesticide has increased proportionally to 0.98% of the total worldwide pesticide market, growing at a rate of just over 13% per annum, representing an increase of 47% between 2004/2005 and 2007/2008. Fungal biopesticides represent a large proportion of the rapidly growing sector of pest management [6].


Several commercial applications of mycopestocides have been investigated, as described below.

[edit] Culicoides nubeculosus Biting Midge and the Bluetongue virus

Sheep infected with Bluetongue Virus
Sheep infected with Bluetongue Virus[22]

The Bluetongue Virus (BTV), transmitted through populations of cattle by Culicoides nubeculosus causing Bluetongue disease, is a potentially death-inducing virus[23][24]. When an animal is infected, it can develop a fever, high salivation, and cyanosis of the tongue, hence the name 'Bluetongue disease'. Losses have been estimated of causing upwards of $3 billion per year[23].

BTV awareness has increased in recent years due to expansion of its range into newly colonized areas, exacerbated by climate change. As a result of the expanding range of the virus, direct losses from sheep and cattle as well as indirect losses from quarantining have caused great economical losses. Although vaccination can eventually control an outbreak such as this, a vaccine for a recent outbreak only made it into the field 18 months after the initial epidemic[24]. Metarhizium anisopliae strain V275 and several other fungi were tested to see their efficacy of control on Culicoides nubeculosus, the disseminator of BTV. M. anisopliae strain V275 ensured a 100% mortality rate within the colonies of the biting midge, with sporulation occurring on the midge cadavers[24]. The high infectiousness and virulence of the fungi will limit the amount of blood meals taken, therefore reducing the probability of the disease vector being acquired and dispersed. Metarhizium anisopliae strain V275 is already commercially available in the USA, sold as F52 by Novozymes[24]. The initial infrastructure requirement is low, so this method can be a cost-effective way of limiting arboviruses. The fungi poses no risk to other wildlife, including humans, birds, fish, and the like, so environmental damage is limited to the pest itself. Although the fungus shows great efficacy as a method of biting midge management, further large-scale trials are needed to better determine the possibility as well as method of using Metarhizium anisopliae strain V275 as a mycoinsecticide in a commercial environment[24].

[edit] Adult Housefly management in poultry farms using Beauveria bassiana

Fly colonized by Beauveria bassiana
Fly colonized by Beauveria bassiana[25]

The common housefly is a constant pest to most people, having a short life cycle and being able to reproduce large amounts of offspring[26]. Poultry manure, being slightly moist, is an optimal habitat for the development of large populations of the housefly. When flies occur in a large-scale, high rise, caged-layer poultry facilities, exponential population expansion can occur[27]. The large numbers of flies are potentially released into the environment, causing distress for neighbours and local businesses[27]. Flies also carry several pathogenic organisms affecting humans, poultry and several other species, and can act as a vector for their dispersal[26]. The defecation and regurgitation that flies perform can also cause blotching on the structure and equipment in the poultry farm, on the light fixtures, and also on the eggs[26], therefore reducing the potential marketability of the final product.

As an attempt to reduce the amount of flies present in a commercial poultry facility, a commercially available product, balEnce, was used to determine the efficacy Beauveria bassiana as a mycopesticide[27]. Since the fungus is non-pathogenic to humans, poultry, and many other organisms, B. bassiana was sprayed throughout a facility. This allowed efficacy of B. bassiana to be compared to another well-known insect neurotoxin, pyrethrin[27]. Adult fly populations were lower in the B. bassiana facility vs. the pyrethrin facility, as well as reducing the number of fly larvae by over one-half when compared to the pyrethrin[27]. When the fungi is applied in the manure pits, it colonizes the pit completely and is applied when flies are breeding, killing any flies that come in contact with the manure, as well as any emerging from it. The use of B. bassiana also does not negatively impact the levels of beneficial insects in the population, many of which are natural enemies of the fly[27]. With adulticides like pyrethrin, the chemical does not affect the larvae; therefore, repeated applications are required[27]. Therefore, it can be determined that fewer applications of B. bassiana will lead to a better pest management system, reducing costs. B. bassiana answers the questions on the minds of many large-scale poultry producers: how to kill large amounts of household flies without pesticide residue to damaging my livestock[27].

[edit] Species

See main article: Species

Effective pest management relies on the appropriate matching of a target species with the pathogenic fungal species[28]. Many species and target combinations have been included within the wiki and are summarized in the article above.

[edit] Definitions

See main article: Definitions

[edit] Notes and References

  1. Svetlana Y. Gouli, University of Vermont, Bugwood.org
  2. Louis Tedders, USDA Agricultural Research Service, Bugwood.org
  3. Andrej Kunca, National Forest Centre - Slovakia, Bugwood.org
  4. 4.0 4.1 4.2 Rechcigl, E.J., & Rechcigl N.A. (2000). Biological and Biotechnological Controls of Insect Pests. (1st ed.). Boca Ranton (FL): Lewis.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 Moore, D., Robson, G.D., & Trinci, A.P.J. (2011). 21st Century Guidebook to Fungi. (1st ed.) New York (NY): Cambridge
  6. 6.0 6.1 CPL Business Consultants. (2010). The 2010 Worldwide Biopesticides Market Summary. Wallingford: CAB International.
  7. Vega, F.E., Goettel, M.S., Blackwell, M., Chandler, D., Jackson M.A., Keller, S., et al. (2009). Fungal entomopathogens: new insights on their ecology. Fungal Ecology 2(4), 149-59.
  8. Kenneth, R., Muttath, T.I. & Gerson, U. (1979). Hirsutella thompsonii, a fungal pathogen of mites. I. Biology of the fungus in vitro. Annals of Applied Biology, 91(1), 21–28.
  9. Shah, P.A., & Pell, J.K. (2003). Fungi as Biological Control Agents. Applied Microbiology and Biotechnology, 61(5-6), 413-23.
  10. Seigfried, K. (1998). Use of Fungi for Pest Control in Sustainable Agriculture. Phytoprotection, 79(4), 56-60.
  11. 11.0 11.1 Misra, H.P. (2005). Weed Management Through Fungal Herbicides. Orissa Review. 53-56
  12. Motlagh, M.R.S. & Javadzadeh, A. (2010). Study of Alternaria pellucida as a promising mycoherbicide for controlling Arrowhead (Sagitaria trifolia) in paddy fields. Proteomics Journal, 3(6), 172-6.
  13. 13.0 13.1 Wraight, S.P. & Carruthers, R.I. (1998). Production, Delivery, and Use of Mycoinsecticides for Control of Insect Pests on Field Crops. Methods in Biotechnology, (5), 233-69.
  14. Jeffries, P. (1995). Biology and Ecology of Mycoparasitism. Canadian Journal of Botany. 73(1), 1284-1290.
  15. Boland, G. J., & Kuykendall, L. (1998). Plant-microbe interactions and biological control. (1st ed.). New York (NY): Marcel Dekker
  16. Cheng, C., Yang, C., & Peng, K. (2012). Antagonism of Trichoderma harzianum ETS 323 on Botrytis cinerea Mycelium in Culture Conditions. Phytophatology 102(11), 1054-63.
  17. 17.0 17.1 17.2 Milner, R.J. & Pereira R.M. (2007). Microbial control of urban pests - cockroaches, ants and termites. Field Manual of Techniques in Invertebrate Pathology, 20(2), 695-711
  18. 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
  19. 19.0 19.1 Lacey, L.A., Frutos, R., Kaya, H.K., & Vail, P. (2001). Insect Pathogens as Biological Control Agents: Do They Have a Future? Biological control, 21(3), 230-48
  20. Tucker, R.K. & Haegele H.A. (1970). Eggshell Thinning as Influenced by Method of DDT Exposure. Bulletin of Environmental Contamination and Toxicology. 5(3), 191-4.
  21. Market Publishers. (2010). Global Biopesticides Market Trends & Forecasts (2012 - 2017). Birmingham: Market Publishers Report Database.
  22. P. Mellor, Institute of Animal Health, bluetonguevirus.org
  23. 23.0 23.1 Mellor, P.S., & Wittmann, E.J. (2002). Bluetongue Virus in the Mediterranean Basin 1998±2001. The Veterinary Journal, (164), 20-37.
  24. 24.0 24.1 24.2 24.3 24.4 Ansari. M.A., Pope, E.C., Carpenter, S., Scholte, E., & Butt T.M. (2011). Entomopathogenic Fungus as a Biological Control for an Important Vector of Livestock Disease: The Culicoides Biting Midge. PlosOne, 6(1), 1-8.
  25. N. Meyling, Sevas Educational Society, sbioinformatics.com
  26. 26.0 26.1 26.2 Axtell, R.C., (1999). Poultry integrated pest management: Status and future. Integrated Pest Management Reviews, (4), 53–73.
  27. 27.0 27.1 27.2 27.3 27.4 27.5 27.6 27.7 Kaufman, P.E., Reasor, C., Rutz, D.A., Ketzis J.K., & Arends, J.J. (2005). Evaluation of Beauveria bassiana applications against adult house Xy, Musca domestica, in commercial caged-layer poultry facilities in New York state. Biological Control, (33), 360-367.
  28. Singh, A., Parmar, N., & Kuhad, R.C. (2011). Bioaugmentation, biostimulation and biocontrol. (28th ed.). Noida (India): Springer
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