Biological Control of Agricultural Pests (including Biobased Pest Management)
From Science Online
Contents |
Introduction
With a booming agricultural market, the United States is a vital world producer of agricultural yield. However, production is limited by the degree to which agricultural pests can be controlled(USDA). An existent problem since early farming by the nation's first inhabitants, the prevalence of agricultural pests exists throughout the world. And in our modern society, pests are becoming even more of a hazard since modern transportation has opened an "invasion window" on a global scale(Oxford, 2007). Though vital to the health of agriculture, pest control using seemingly necessary synthetic pesticides can cause harm to humans and the environment
Another alternative to the use of synthetic pesticides is biobased pest management in crops. Biobased pest management has the goal of providing safer and more effective methods of controlling pests while reducing our reliance on synthetic pesticides(USDA). There are five primary types of biobased pest management that are utilized throughout the US, but the most effective is biological control. Biological control is the supression of pests through the introduction of natural enemies. This method encompasses natural enemies that include parasites, predators, and diseases (USDA).
Most commonly practiced in the US, Australia, Aouth Africa, Canada, and New Zealand, this form of Improved Pest Managemant (IMP) offers the only safe, economic, and environmentally sustainable solution to control destructive and invasive species(Gunasekaran)(McFadyen, 1998). Subcategories of agronomic control include date of planting, crop rotation, intercropping, and selection of early maturing varieties(USDA). However, biological pest management is recognized as the most effective, safest alternative which, unlike pesticides, aims to only target specific problem species rather than every insect in the crop(Hayward, 2007).
Parasitic Pest Control
Parasitic pest control is the maitenance of agricultural pests through the introduction of natural parasites. Through this process, natural parasites are introduced into an agricultural ecosystem to eliminate harmful, invasive species, while not affecting the crop itself. An example of this form of biological control is the common wasp. This wasp lays eggs inside an aphid and allows its young to develop. The young grow inside the host, killing it as they mature, and emerge as adults to continue the cycle(Cornell University).
There are important advantages and disadvantages to this fragile process. With respect to impact on species, parasitic pest control does an effective job of eliminating unwanted pests and, if properly used, it has no negative impacts on untargeted species in the region. It is a ver slow going process, but environmentally, this form of biological pest control is quite specific(Gunasekaran). In order for the method to be effective, farmers must identify a form of parasite that has no adverse effects of the crop itself or on neighboring ecosystems (Cornell University). They must identify a parasite that will not have exponential and uncontrolled growth once it has done its job. Economically, this process' benefits greatly outweigh the costs. Though some forms of parasites may be more expensive than others to acquire, the limited damage done to the environment and the effective nature of the process outweighs the drawbacks.
Unlike synthetic pesticides, parasitic pest control has very minimal negative impact on humans. Since the parasites can be eliminated through cleaning methods once the crop has been harvested, they are not a threat to human health in short term or long term retrospect. Parasites that may pose a threat to human or agricultural health, on the other hand, are regulated by the Quarantine Inspection Service or the Biological Control Act of 1984 prior to application. Once the parasite has passed this legislative control, it may then be used on crops(McFadyen, 1998). Unsuccessful drawbacks to this method, on the other hand, iclude the length of time it takes for the parasites to do their job. Once introduced to an endangered ecosystem, the parasites invade the harmful species and work to eliminate the threat. However, often times crops are already destroyed by the time the parasites are able to actually eliminate the invasive pests(Hayward, 2007).
Parasitic pest conrol is an effective means of biological control, but is a more tedious method of pest elimination. In order for this form of biological control to be effective, farmers would need to identify the types of pests they forsee having prior to the growing season, and subsequently release the parasites prior to the population explosion of the pest.
Pest Control through Natural Predators
The introduction of natural predators of invasive species is another means of biological control. When invasive species arrive, they come without their natural predators. If no predators of this species exist in the area of inhabitants, the pest can grow to uncontrollable levels. If the burden of an agricultural pest becomes to heavy to bear, natural predators of this species are reintroduced to minimize its population size(Gunasekaran). An example of this form of biological control is the lady beetle.Well known predatory insects, lady beetles consumeinsects and mites throughout their lifetime(Cornell University).
Advantages and disadvantages to this process are an important topic of interest in the agricultural world. With respect to species, this is an effective means of elimination of pests and regular release of many different natural predators is used to control thrips, leafminers, and other insects(Amberg, 2007). However, it drastically changes the structure behind previously existing ecological niches. The sudden introduction of a powerful new species can throw off the ecological equilibrium that was previously met in the region. Once this new species is introduced, it could prey on unrelated organisms that may aid in plant growth and development. Because of this, often times different crops are planted nearby to draw pests away from primary agricultural fields(Amberg, 2007). Economically, the costs and benefits sit at a fragile balance. The aquistion and transportation of specific natural predators often times is a more expensive process than others, and the difference it makes in agricultural production is less than significant. Though this method of biological control may seem ideal, the environmental and economic risks and costs slightly outweigh the benefits of the program (McFadyen, 1998).
Similar to that of parasitic pest control, the introduction of predators has little impact on humans, though many may prove to be subtle neusances to humans inhabiting the region. Since some predators can disrupt ecological niches, countries are careful as to what species tey allow to be moved from place to place. The federal Plant Pest Act of 1957 and the Plant Protection Act of 1990 were two forms of legislation put into place to prevent the introduction of insect pests and to regulate the movement of insects from different locations(Gunasekaran).
Two examples of predatory control exist in Australia and South Africa. In South Africa, mealybugs are utilized to isolate infestations of unwanted pests in cacti. In Australia, the Cyrtobagous salviniae weevil is released to manage pests that inhabit the floating fern salvinia(McFadyen, 1998).
Pest control via the introduction of natural predators is an effective means of biological control, but is a very specific practice. The fragile nature in ecological niches inhibits the full extent to which this method can be utilized. Nevertheless, when properly practiced, this method can eliminate invasive species with little to no difficulty.
Pest Control through the Introduction of Disease
The introduction of disease into an ecosystem is the least commonly used practice of biological control. It involves the introduction of various pathogens to a crop in order to eliminate invasive pest species, while leaving the plant virtually unharmed(McFadyen, 1998). It is a fragile process due to the nature of the procedure and several pieces of legislation control the application of this method. The Quarantine Act works to keep out harmful or suspicious diseases and pests, while the Wildlife Protection Act controls trade in endangered wildlife, including many endangered species that may be affected by the diseases(McFadyen, 1998). An example of this form of biological control was noted by Dr. Mark Parrella of the University of California. He worked with the introduction of a naturally occuring fungus that showed excellent control on flow thrips and symphylans. This fungus was so effective in doing its job that it is even being looked at as a replacement for methyl bromide, a common but dangerous pesticide(Amberg, 2007).
Unfortunately, the disadvantages in this process slightly outweigh the advantages. With respect to species, this form of biological control definently does its job of eliminating unwanted pests. For example, a nematoda is a pathogen that quickly kills its invasive host. Other pathogens include bacteria, viruses, fungi, and protazoa(Cornell University). However, there are very fine lines drawn with respect to the exact targets of these dangerous pathogens. Oftentimes, uninvolved species are negatively impacted by the introduction of disease. Economically, this procedure is difficult as well because occasionally the aquisition of various strains of disease and the controlled application of the pathogens can cost more than profit reaped from undamaged crops. Environmentally, it is a touchy topic as well. The introduction of disease into crop as a from of biological control is a seemingly natural process and it does not destroy or tarnish the environment, however, it can negatively impact balance in some ecosystems with respect to non-target species.
Though it may seem this form of biological control is only associated with negative impacts, it is an effective form of biobased pest management. Weeds are the most significant of the economic and environmental pests and they can often times dominated entire ecosystems(McFadyen, 1998).With the help of the TNRD Noxious Weed Control Program, weeds can be targeted by arthropods, vertebrates, and pathogens for efficient removal from crops, with very limited risks(Hayward, 2007)(Cornell University). Though the process, as a whole, is a very fragile one, it is a safer and more beneficial from of invasive species elimination than the use of pesticides.
Overview and Alternate Options
The three primary forms of biological control are: parasitic control, pest control through the introduction of natural predators, and pest control through the introduction of disease. Other forms of biobased pest management include manipulation of plant volatiles and the "Sterile Insect Technique". Since plants naturally release clouds of chemicals and scents, manipulation of plant volatiles could affect insect behavior since insects, pest, and pollinators use volatiles to locate and asses the quality of plants(Amberg, 2007). The "Sterile Insect Technique" uses the release of sterile males of a species into wild populations to control the growth of invasive species by confusing natural reproduction(Amberg, 2007).
Each technique has its own advantages and disadvantages, but all offer safer, more effective means of pest management than pesticides. A globally growing practice, biobased pest management is gaining popularity and recognition throughout the farming community. Hopefully, with the continued increase in interest towards this process, society can drift from the simplistic shackles of pesticide use and continue to discover newer, healthier means of pest control.
References
Journal References
Amberg, Robert (2007). "Symposium focused on IMP for horticulture" American Farm.
Oxford, University (2007). "Invasive Species Take to the Air" Science Daily. pp.undefined-undefined.
News ReferencesWeb References
Cornell University. Biological Control: A Guide to Natural Enemies in North America.
