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Problems with Current Pest Control Techniques

Small Molecule Pesticides

Small molecule pesticides or bio-pesticides are unconventional pesticides that use substances which make up, or are produced, by plants and animals. Examples of these bio-pesticides include pheromones, enzymes, hormones, and even micro-organisms as a method of pest control [2]. These types of pesticides are excellent alternatives to traditional chemical pesticides. Advantages of this type of pesticide include low inherent-toxicity to target and non-target organisms, low persistence in the environment, and low likelihood of selecting for pest resistance [2]. Disadvantages of bio-pesticides include a typically slower mortality rate for the pests as well as a higher susceptibility to variable environmental conditions [3]. There is also an issue of properly storing pesticides that are made out of biomolecules. One of the most well-known examples of small molecule pesticides is DDT (Dichlorodiphenyltrichloroethane). Short term studies have shown that the potential benefits outweighed the risks. However, the stability of DDT, persistence in the environment, accumulation in adipose tissue, and potential estrogenic properties raise concerns over long term use. Accumulation through the trophic levels leads to adverse side effects such as thinning of falcon eggshells, leading to population decline [4].

Biological Pest Control

Biological pest control involves the use of natural predators against pests. In many cases, the pests are invasive species which have escaped from their natural ecosystem. When the natural predator of the pest is not present, the pest has the opportunity to proliferate without control [5]. Natural predators are then imported after pre- and post-release testing is done. Pre-release testing involves testing the natural predator to ensure it will not take over and proliferate in the ecosystem itself, as well as non-target testing to ensure beneficial species will not be targeted [6]. Testing is initially done in the lab; once there is enough data supporting the efficacy of the predator, field tests are done. Field tests give a better representation of what to expect post-release. Upon government approval, the predator is released into the ecosystem. Potential downfalls of biological pest control include predatory species becoming an alpha predator in the food chain, or becoming an invasive species itself [7].

Mechanical Pest Control

Mechanical pest control involves the use of physical means to control pests. Some examples of mechanical pest control methods include insect traps, physical barriers, or weed pulling. These control mechanisms are advantageous in terms of minimizing off-target effects, and are generally environmentally friendly. However, these methods can be laborious and are often not feasible for implementation on commercial crops. Recent research has aimed to decrease the amount of labor required to pull weeds from commercial crops by using computer vision-guided machines [8]. Initial results with computer guided machines has shown promising results, producing weed reductions in the range of 62-87%. However, this research requires more development in order to be mainstream in commercial agriculture.

Crop Rotation

Crop rotation is an agricultural method in which different species of crops are grown in the same area of land to promote nutrient renewal within the soil. In addition, crop rotation aids in crop yield, soil quality, and controls the build-up of weeds, pests, and other diseases that might be specific to the crop. However, crop rotation can limit the variety of crops a farmer is able to grow in their field due to specific rotation patterns. Each season, these crops need to be monitored in order to control the likelihood of diseases being carried over to the next crop. This may be limiting for farmers because of the constraints associated with which crops they are able to plant and at what time they can be planted. In addition, certain crops require specific machinery which may be expensive for farmers [9].

An example of an important crop produced throughout the world is canola. It is used to make canola oil which is a key ingredient in many foods, cosmetics, and biodiesels. When canola crops are rotated with barley, oats, or wheat, the lowest number of diseases carry over from the previous crop which in turn increases yields of the canola crop. Most other crops such as corn, flax, potato, and sunflower require wait times of up to three years before they can be planted to prevent a buildup of diseases common to both the respective plant and canola [10].

Crop Burning

Another method of pest control involves crop burning, which is the process of setting fire to crop residues after harvest seasons to clear large areas of land. Remaining pests on particular crops are killed in order to prepare the soil for the following season. Crop burning is considered a quick and easy method for clearing farmland, but it is usually only used by farmers when other methods for clearing pests is unsuccessful. A burning permit is required by farmers interested in crop burning, which may end up being expensive if used continuously [11]. Bigger risks that come with crop burning include air pollution, soil pollution, and an increase in soil erosion from wind and water. Crop burning also has a big impact in local ecosystems surrounding farm land [12].

Buffer Zones

Buffer Zones are placed between organic crop fields and fields containing genetically modified (GM) crops to protect the organic farms from any contact or contamination, keeping organic crops as close to organic as possible. Contamination of organic crops by GM crops can occur through many different methods such as: gene transfer through cross-pollination, seed translocation, and contact with inorganic pesticides [13]. Wheat pollen has been detected to travel up to 50 meters via pollen drift [13] therefore, buffer zones must be greater than 50 meters to have an impact. A 200 meter buffer zone is not enough to stop pollen-mediated genetic antibiotic and drug resistance [15]. When commercial scale equipment is used in harvest, an extra 50 metres is added on to the required distance between the wheat trials [14]. This extra distances helps to protect organic crops from any other form of contamination that could be transferred by the machines. In order to effectively protect organic crops from contamination the distance required for isolation should be further tested and increased.

References

1. Agriculture and Agri-Food Canda. (2014). Biopesticides Priority Setting 2014. Government of Canada, http://www.agr.gc.ca/eng/?id=1411590428019.
2. Agriculture and Agri-Food Canada. (2013). Categories of Biopesticides and Related Products. Government of Canada, http://www.agr.gc.ca/eng/?id=1299080205554.
3. Chandler, D., Bailey, A.S., Tatchell, G.M., Davidson, G., Greaves, J. & Grant, W.J. (2011). The development, regulation and use of biopesticides for integrated pest management. Phil. Trans. R. Soc. B, doi:10.1098/rstb.2010.0390.
4. Turusov, V., Rakitsky, V., & Tomatis, L. (2002). Dichlorodiphenyltrichloroethane (DDT): ubiquity, persistence, and risks. Environmental health perspectives, 110(2), 125.
5. Flint, M. L., Dreistadt, S. H., & Clark, J. K. (1998). Natural enemies handbook: the illustrated guide to biological pest control (Vol. 3386). Univ of California Press.
6. Follett, P., & Duan, J. J. (Eds.). (2012). Nontarget effects of biological control. Springer Science & Business Media.
7. Louda, S. M., Pemberton, R. W., Johnson, M. T., & Follett, P. (2003). Nontarget Effects-The Achilles' Heel of Biological Control? Retrospective Analyses to Reduce Risk Associated with Biocontrol Introductions*. Annual Review of Entomology, 48(1), 365-396.
8. Tillett, N. D., Hague, T., Grundy, A. C., & Dedousis, A. P. (2008). Mechanical within-row weed control for transplanted crops using computer vision.Biosystems Engineering, 99(2), 171-178.
9. Iain Robson. (2013). Crop rotation definition and benefits. Web.http://myfarmeducation.ca/farming/crop-rotation-definition-and-benefits10. Canola Council of Canada. (2014).
10. Crop Rotation. Web. http://www.canolacouncil.org/canola-encyclopedia/field-characteristics/crop-rotation
11. Department of Ecology, State of Washington. (2012). Agricultural Burning. Web.
12. The State of Victoria. (2015). Stubble burning. Web. http://agriculture.vic.gov.au/agriculture/grains-and-other-crops/crop-production/stubble-burning
13. Belcher, K., Nolan, J. & Phillips, P.W.B. (2005). Genetically modified crops and agricultural landscapes: spatial patterns of contamination. Ecological Economics, 53(3), 387-401.
14. Canadian Food Inspection Agency. (2015). Directive Dir2000-07: Conducting Confined Research Field Trials of Plant with Novel Traits in Canada. Government of Canada. http://www.inspection.gc.ca/plants/plants-with-novel-traits/applicants/directive-dir2000-07/eng/1304474667559/1304474738697.
15. Sirinathsinghji, E. (2012). Behind the GM Wheat Trial. Science in Society, 55, 6-7.