Introduction
Super weeds have become a disturbing phenomenon in the world of genetically modified crops. It is imperative to understand how the phenomenon arose, its manifestations and effects on farmers and other stakeholders. This would allow one to suggest possible ways of resolving the problem.
Origin
Vinay and Jadav (167) explain that super weeds emerge from genetically modified gene transfer. Genetically, modified crops have certain characteristics that allow them to resist herbicides. Normally, the plant may possess a gene that codes for unique proteins in the crop. Once the plant comes in contact with herbicide, it detoxifies it and continues to survive. This means farmers can spray entire fields with herbicide and not worry about the possibility of loosing their crops.
However, through various natural methods, genes from the genetically modified crops can spread into related weeds and thus transfer the herbicide resistant quality. One should note that gene transfer is only possible when the herbicide-resistant crop and the weed are genetically related. For instance, the wild mustard is a weed that has close genetic similarity to oil seed rape. This breeds a super weed that is non-responsive to herbicides or responsive only to high amounts of herbicide (Wisler & Norris 918)
Manifestations
Super weeds are a widespread problem in American Southern States. Most soybean farmers have born the brunt of this phenomenon owing to the Roundup variety. Roundup is a popular weed killer that was extensively used in the South; its active ingredient is glyphosate. The company that manufacturers the herbicide – Monsanto – also patented Roundup-ready soybeans.
These are genetically modified crops which resist Roundup’s glyphosate. Farmers have adopted the use of both the herbicide and the herbicide resistant crop in large percentages. Currently, use of this combination is between 85-90% (Vinay & Jadav 168). Many agriculturalists preferred this method because it appeared to save on costs.
Furthermore, it simplified the weed-control process, which was quite complicated when used on crops without herbicide resistance. Farmers in Arkansas, Tennessee, Missouri, Georgia and North Carolina have reported the existence of super weeds. One of the largest varieties is pigweed which grows at a rapid rate and leads to the emergence of very strong weeds. Severe cases have caused farmers to use hand weeding as a way of eradicating them as some weeds cannot be removed through machine work.
Another popular weed in the US is horseweed which requires a heavy dose of herbicides. Estimates indicate that one must spray as much as eight times more herbicide than conventional weeds. This weed is prevalent in New Jersey, Ohio, Indiana and seven other southern states. The waterhemp is also another glyphosate resistant weed that is prevalent in Illinois and Iowa (Hayden et. al. 820).
Aside from soybean farming, the problem is also evident in sugar beets in countries such as Germany. However, these were experiments that were conducted by scientists. Their findings indicate that the same phenomenon is likely to arise during the growth of these types of plants. Argentina and Canada have also reported similar problems in the growth of oil seed rape (Owen 99).
Consequences of the super weed
Since the super weed already has desirable characteristics, then natural selection would favor it over other weeds. Many farmers have reported an increase in the growth rate and prevalence of super weeds. Several cultivators have to employ aggressive methods to get rid of the species (Clark & Yamaguchi 18). The most common approach is use of highly toxic herbicides or different varieties of herbicides. Farmers have to spend more on such powerful herbicides, which makes their agricultural enterprises less profitable.
Having to use other alternatives would also frustrate farmers because they opted for genetically modified, herb resistant crops in order to save money. They would be paying premiums for a form of technology that is not yielding any benefits. Farmers chose the methods because they wanted to use fewer herbicides. Therefore, if a GM product is causing them to use more, then this beats the purpose of its introduction (Pimentel 52).
Other famers have resulted to older herbicides, which became unpopular because of their effect on human beings. For instance, the chemical 2.4-D was a herbicide that fell out of favor. It has been associated with the spread of cancer and reproductive impairment.
In fact, countries like Denmark and Norway have banned its use. Such levels of toxicity affect the people who consume those crops, albeit in the long term. Excessive herbicide dependence also leads to environmental degradation, which is a big problem for agricultural sustainability goals. If farmers continue to use excessive quantities of herbicides, then these chemicals could slip into groundwater and degrade the environment (Patzoldt et. al. 711).
Makers of the herbicide-resistant, genetically –modified crops ask farmers to practice crop alterations. However, this may not always be easy for farmers who have specialized in the growth of certain crops. Furthermore, many of them will loose a substantial investment in the GM crops as the products are more costly than conventional crops.
They have entered into licensing agreements with Monsanto and other GM producers, so it is difficult for them to simply switch to other products. Farmers are often penalized for saving seeds, so they would have to purchase new ones in the event that they are interested in switching to other crops. This would be quite uneconomical for them and the rest of the population.
Many farmers are also worried about the future of the super weed. It is likely that if the phenomenon was prevalent in oil seed rape and soybeans, then it can manifest among other genetically modified crops. Furthermore, agriculturalists are not certain about the genetic manifestations of the super weeds. It is likely that native plant populations will favor an introduced gene over the conventional one (Perez & Kogan 19). This will inhibit normal evolutionary processes and thus increase the population of super weeds in most of these fields.
Genetic ways of preventing super weed occurrence
As stated earlier, super weeds arise from genetic transfer between herbicide resistant plants and genetically similar weeds. Stakeholders can prevent the possibility of this transfer through a number of genetic methodologies. It should be noted that most of them are costly and are yet to be proven in large-scale crop fields.
If genetically modified crops cannot be eliminated, then the nature of plants used may be altered. The transfer of pollen is the commonest method of pollen transfer between organisms. Therefore, farmers who want to prevent the development of super weeds have the alternative of using vegetative seeds. Geneticists refer to these types of seeds as adoximis; they do not have compatible pollen and will not facilitate gene transfer. However, commercial companies are yet to explore the area fully.
Another way in which stakeholders can prevent the occurrence of super weeds is through selection of location of where to plant the herbicide resistance GM seeds. The process is known as cytogenetic mapping. For genetic transfer to occur between weeds and crops, chromosomes from both species have to be similar.
For instance, genome D in wheat is only compatible with genome D in bearded goat grass leading to the development of a super weed. However, if the genome finds a weed with incompatible chromosomes, then no interaction will occur. Scientists have the ability to locate areas that contain transgenic lines through cytogenetic mapping. They can take selected seeds to areas without compatible genes and this minimizes the risk of genetic transfer (Gressel 364).
Transgenetic mitigation could also be another alternative to the growth of super weeds. This occurs by creating genetically engineered seeds that contain a harmful trait for weeds but a neutral one for the crop. For instance, dwarfing is the process by which crops are genetically engineered to become shorter than their unmodified counterparts.
This allows them to increase yield and minimizes their chances of falling over. If a herbicide resistance plant has been dwarfed, then it will transfer the same trait to genetically similar weeds. The trait would be detrimental to weeds as their survival depends on how well they compete with plants. They would not be able to secure light (Neve et. al. 681).
Conclusion
Superweeds lead to the use of excessive herbicides, a lot of manpower and decreases in crop yields. Farmers, agricultural companies and geneticists need to rethink the use of these groups as they lead to many unwanted consequences. Alternatively, some genetic solutions could be considered, such as transgenetic mitigation and cytogenetic mapping, however, these methods are yet to proven in real-life farm settings. Consequently, their practical use could take a long time.
Works Cited
Clark, Marshall & Isamu Yamaguchi. Agrochemical Resistance: Extent, Mechanism & Detection. Oxford: Oxford University Press, 2001. Print.
Gressel, Jonathan. “Tandem constructs: preventing the rise of super weeds.” Tibtech Sep. 1999: 362-368. Print.
Hayden, Zachary, Daniel Brainard, Ben Henshaw and Mathieu Ngouajio. “Annual Weed Suppression in Rye–Vetch Cover Crop Mixtures.” Weed Technology 26.4(2012): 818-825. Print.
Neve, P, A Diggle, F Smith & S Powles. “Simulating evolution of glyphosate resistance in Lolium rigidum II.” Weed Research 43(2003): 678-682.
Owen, Michael. Herbicide resistance in weeds: What is the nature of the problem? NY: The National Academies Press, 2012. Print.
Patzoldt, William, Patrick Tranel, & Aaron Hager. “Variable herbicide responses among Illinois waterhemp (Amaranthusrudis and A tuberculatus) populations.” Crop Protection, 21(2002): 707-712. Print.
Perez, A & M Kogan. “Glyphosate resistant Loliummultiflorum in Chilean orchards.” Weed Research 43.12 (2003):19. Print.
Pimentel, David. Encyclopedia of Pest Management. New York: Marcel Dekker Inc., 2007. Print.
Vinay, Gaur & P Jadav. “Super weed – A threat of GM Crops.” Journal of Advances in Development Research 1.2(201): 167-169. Print
Wisler, Gail & Robert Norris. “Interactions between weeds and cultivated plants as related to management of plant pathogens.” Weed Science 53.6(2005): 914-917. Print.