Advantages and Disadvantages

From BIOL 2P96 Jan 2013 Group 07

Revision as of 13:18, 22 March 2013 by Jv07cx (Talk | contribs)
(diff) ←Older revision | Current revision (diff) | Newer revision→ (diff)
Jump to: navigation, search

[edit] Advantages and Disadvantages of Using Entomogenous Fungi as Biocontrol Agents of Arthropod Pests

There has been a great amount of research effort dedicated to attempting to employ pest diseases and pathogens into biocontrol agents that can be used to attack those arthropods society views as pests. Biological control is described as the practice by which the undesirable effects of a pest organism are reduced through the activity of another organism that is not the host, is not a pest or isn’t a human. [1]


Synthetic chemical pesticides have been important in arthropod control since the discovery of DDT in the 1930’s and they remain the most important method today because they:[2]

  • Have a broad spectrum usually being effective for more then one pest;
  • Being highly effective;
  • Are affordable, and easy to make;
  • Are persistent, able to kill throughout the season or life of the crop.

They have served society well by reducing the economic damage caused by arthropod pests and by reducing the occurrence of the diseases of plants and animals that are transmitted by these pests because of this combination of properties. However these same characteristics have also created the problems widely associated with the use of chemical pesticides. The tenacity and the widespread use of chemical pesticides has resulted in them becoming unnatural mechanisms of the environment resulting in: [3]

  • Development of resistance in arthropod pest populations;
  • Appearance of new types of pests as old ones vanish;
  • Elimination of the natural predators or enemies of pests;
  • Disruption of natural ecosystem balance as non pests are also killed;
  • Bioaccumulation of pesticides through food chains, adversely affecting mammal and bird populations.

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. [4]


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. [6].


Verticillium (Lecanicillium) lecanii is a species of pathogenic fungi effective on Myzus persicae and other aphids on chrysanthemums mostly due to the fact that the crop is grown in a greenhouse in which humidity can be controlled. Vertalac® is the brand name of the commercial formulation containing spores of Verticillium (Lecanicillium) lecanii used to control aphids and the whitefly. [6].


Although it is much more difficult to use entomogenous fungi for biological pest control in the field, there is promise for it for pests that have an aquatic stage such as using insect fungal pathogens for control of diseases such as malaria that depend on insect vectors.[7] Several fungi are already in use and have promise to be in use in the near future. Researchers are using model bacterium such as Bacillus thuringiensis to provide insights to the development of fungal biocontrol agents (mycoinsecticides), providing understanding into their pathogenic process, enzymes involved with the penetration of arthropod host cuticle and the role of insecticidal fungal toxins. Transgenic plants expressing endotoxin genes from Bacillus thuringiensis have been made to protect certain crops such as tobacco, cotton, and maize against attack from pests. This same technology is being applied to toxins being produced by entomogenous fungi. [8]


It has been suggested by Lacey et al. (2001)[6] that increased use of microbial biological control agents as alternatives to broad-spectrum chemical pesticides depends on (especially in utilizing fungi as biocontrol agents):

  • Increased pathogen virulence and speed of kill;
  • Improved performance under unfavorable environmental conditions;
  • Greater efficiency in production
  • Improvements in formulation that enable ease of application, increased environmental persistence and longer shelf life;
  • Greater appreciation of their environmental advantages;
  • And wider acceptance by growers and the general public.

To take full advantage of the epizootic potential of fungi, scientists and crop growers need to understand not only the factors that are critical for fungal virulence and infection but also the procedures to exert control over them through optimization of culture methods, formulation, and environmental manipulation. Effective use of entomopathogenic fungi as microbial control agents will eventually depend on the use of the right propagule, formulated in an ideal manner and applied at a suitable dosage and time. Timing will depend on the incidence of vulnerable host stages, good environmental conditions, and proper planning with other agricultural methods (avoiding fungicides, finding the right time to water crops, etc.).[6]


Further improvement in the microbial control activity of entomopathogenic fungi can be expected by their combination with other interventions and technologies, use of other biological control agents, use of environmental manipulation to favor the infection processes, and use of targeted pests to aid in the dissemination of fungus. For example, the use of scented chemicals in traps that attract adult insects and contaminate them with fungal spores will not only control the attracted insects, but also enable auto dissemination of the fungi into harder to treat larval habitats such as soil.[9]


[edit] Notes and References

  1. Lacey et al. (2001). Insect pathogens as biological control agents: do they have a future? Biological Control. 21: 230-248. DOI: http://dx.doi.org/10.1006/bcon.2001.0938
  2. D. Moore, G. Robson, and A. Trinci. (2012). Fungi as pathogens of animals, including humans, CH 16. of 21st Century Guidebook to Fungi. pgs. 421-422.
  3. D. Moore, G. Robson, and A. Trinci. (2012). Fungi as pathogens of animals, including humans, CH 16. of 21st Century Guidebook to Fungi. pgs. 421-422.
  4. Lacey et al. (2001). Insect pathogens as biological control agents: do they have a future? Biological Control. 21: 230-248. DOI: http://dx.doi.org/10.1006/bcon.2001.0938
  5. 5.0 5.1 5.2 D. Moore, G. Robson, and A. Trinci. (2012). Fungi as pathogens of animals, including humans, CH 16. of 21st Century Guidebook to Fungi. pgs. 421-422.
  6. 6.0 6.1 6.2 6.3 Lacey et al. (2001). Insect pathogens as biological control agents: do they have a future? Biological Control. 21: 230-248. DOI: http://dx.doi.org/10.1006/bcon.2001.0938
  7. Charnley, A and Collins, S. (2007). Entomopathogenic Fungi and Their Role in Pest Control. Environmental and Microbial Relationships 2nd Ed: 159-187.
  8. Charnley, A and Collins, S. (2007). Entomopathogenic Fungi and Their Role in Pest Control. Environmental and Microbial Relationships 2nd Ed: 159-187.
  9. Charnley, A and Collins, S. (2007). Entomopathogenic Fungi and Their Role in Pest Control. Environmental and Microbial Relationships 2nd Ed: 159-187.
Personal tools
Bookmark and Share