Introduction:
Herbicide resistance in Australia costs billions of dollars a year affecting natural systems but more particularly agricultural cropping systems. The Department of Agriculture wants herbicide resistance to be further investigated through this paper. In this briefing paper a range of areas will be covered including mechanisms of herbicide resistant weeds and the major instances. Rye grass or L. rigidum is an ever evolving weed and is the world’s leader in herbicide resistance which has a range of mechanisms which have led to its survival and resistance. But are herbicide resistant weeds like L. rigidum becoming more common if so what are the projections of further evolution to herbicides?
Major instances of herbicide resistance and their mechanisms:
Rye grass (common name) or L. rigidum (scientific name) is a monocotyledon grass weed found in the Australia grain belt, having high genetic diversity and being described as the world’s most dramatic example of resistance evolution (Powles and Preston 2006). L. rigidum has negatively
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affecting crop yields across Australia, a range of herbicides have been used on L. rigidum to combat yield loss but have shown a pattern of brief mortality success followed by failure (S. Manalil, M. Renton, A. Diggle, R. Busi, S. Powles, 2012). This is due to its ability to rapidly evolve to herbicides, more worrying is the fact that resistant populations which include L. rigidum and other species exhibit cross resistance to different herbicides (Q. Yu and S. Powles, 2014). Cross-resistance in L. rigidum shows that individuals can have one to several resistant mechanisms which include target and non-target site resistances (Q. Yu and S. Powles, 2014). Target site resistance arises through plant mutation of a gene coding enzyme which limits herbicide binding (Q. Yu and S. Powles, 2014). Non target site is where resistance involves mechanisms that lowers the amount of active ingredient that reaches the target site (Q. Yu and S. Powles, 2014). It can be understood that Australia has accumulated several levels of mechanism resistance which is the norm across vast areas of Australia for L. rigidum (Powles and Matthews, 1992). Specific mechanisms and major instances: Weeds have evolved to herbicides due to an enhanced metabolic capacity which results in detoxified herbicides or metabolic resistance (Q. Yu and S. Powles, 2014). Metabolic resistance demonstrates its resistance to herbicides through chemical groups and sites of action which can affect the efficiency of new and unreleased herbicides (Q. Yu and S. Powles, 2014). Metabolic resistance first became evident among weedy populations within Australia through L. rigidum (rye grass) during the 1980s (Q. Yu and S. Powles, 2014). The problems arise where weed populations which are strongly diverse are strongly selected with an herbicide which initially works with high mortality rates (Q. Yu and S. Powles, 2014). But within the strongly diverse weed populations there are rare herbicide resistant genes that become selected and favoured leading to resistant evolution which lowers the efficiency of herbicides (Q. Yu and S. Powles, 2014). Specific mechanisms and major instances through effect of glyphosate: Similarly glyphosate resistance which were first discovered in 1996 among rigid ryegrass populations in Australia has extended to several other countries (Pratley et al. 1999). The major mechanisms in glyphosate resistant weeds are that translocation of glyphosate has changed (C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). It has changed through its accumulating of glyphosate in the leaf tips rather than the meristem shoots, amino acid substitutions within target sites have also mutated and account for the another mechanism (C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). The mechanism with lower level resistance is the target site mutation rather than the alternated translocation of glyphosate, these resistant mechanisms are inherited as a single and mostly dominate gene trait (C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). Resistant alleles can be transmitted through both seed and pollen of L. rigidum as it is an obligate outcross (C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). Increasing in extent or species involved: Across the world but particularly in Australia herbicide resistance is becoming more common (Q. Yu and S. Powles, 2014). When understanding why herbicide resistance in agricultural weeds is increasing in species but particularly extent it is often ignored and unappreciated that poor farming techniques result in increased resistance. The main leading causes begin with the intensity of herbicide applied or herbicide rate used which is important in determining resistant mechanism. A high dose rate results in high mortalities and a low rate leaves survivor weeds carrying target site gene mutations which often spread quickly across few generations through cross-pollination (Q. Yu and S. Powles, 2014). Other explanations for high survival is through; poor herbicide application, target weed is large in size, undesirable spray conditions and plant stresses (Q. Yu and S. Powles, 2014). Herbicide resistance is today increasingly recognised in several crop weed species which looms as a threat to the sustainability of herbicides and world food production capacity (Q. Yu and S. Powles, 2014). Species of weeds that have herbicide resistance is increasing on the way up as they evolve with herbicides through selection just like L. rigidum does with cross resistance and metabolic resistance. There are 38 species in Australia that are herbicide resistant (C. Preston, 2011) and much of them over the years have experienced increasing resistance to a diverse range of modes of action (C. Preston, 2011). The biggest problem of herbicide resistance is within species rather than species involved, the resistant 38 species have greater diversity, population numbers and fitness than the non-resistant species (Q. Yu and S. Powles, 2014). The number of species that are herbicide resistant are climbing in Australia from years 1982 to 2015 (Heap, I. 2015). Through the 1980s resistant weeds were at their lowest with only 6 resistant species but this increased further through the 1990s, 2000s and 2010s where for this decade there are currently more than 10 new resistant species (Heap, I. 2015). If resistance continues at the current rate many more weed species and particularly more resistant weeds will be resistant to more modes of actions and herbicides. Projections for the future evolution of resistance in crop weeds: Into the future projections of weeds evolving to herbicides is set to reduce as a better understanding of herbicide genes, causes and solutions is reached. Herbicide resistance is becoming better understood through new technologies which help us understand the genes of weeds that show resistance, this is done through sequencing technologies and transcriptome-gene expressing profile (Q. Yu and S. Powles, 2014). Through these new technologies better herbicides and possibly new genetically modified weeds and crops would result in reduced weed numbers and resistance. But even through all these new technologies and understandings eradication of certain herbicide weeds is difficult and management currently is the most efficient solution (C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). Projections for the future evolution can be reduced through using innovative cultural solution Weed evolution could also be reduced through new cultural solutions such as the cage mill machinery which is a new innovative idea. Cage mill machinery is a proposed idea to combat herbicide resistance and to reduce its use, the idea results in the destruction of seeds where up to 95% of L. rigidum weed seeds alone pass through the harvester (M. J. Walsh, R. B. Harrington, and S. B. Powles, 2011). The cage mill which is attached to the back of the harvester which is used in cropping areas will physically crush and destroy up to 94% of seed weeds passing through (M. J. Walsh, R. B. Harrington, and S. B. Powles, 2011). The idea could drastically reduce the weeds seed bank in cropping systems which will result in more limited evolution ability and reduced herbicide resistance (M. J. Walsh, R. B. Harrington, and S. B. Powles, 2011). Projections for the future evolution of herbicide weeds, how it can be managed? The projections for future evolution depends on what farming practises are adopted. An experiment done by (M. Widderick , 2007) shows that with more often and more timely herbicide applications resulted in a lower proportion of resistant individuals over projected 30 years. The comparison is with keeping everything constant except the times applied, the highest times applied of herbicide which is 30 times over 30 years performed better than the lowest applied times of seven times (M. Widderick , 2007). For the lowest times applied application projections showed that after 20 years almost the whole population would be resistant where applying yearly lead to almost 0% resistant proportion (M. Widderick , 2007). The other experiment provided a 30 year simulation of comparison of conventional tillage to herbicide use (M. Widderick , 2007). It was found that the conventional system of cultivating the soil with no herbicide use over 30 years meant that 0% of the population were resistant compared to over use of herbicides lead to between 50-100% resistant populations (M. Widderick , 2007). These results show that with the right integrated pest management system using a range of solutions including; physical, cultural, biological and chemical controls leads to better outcomes (M. Widderick , 2007; C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). By having more than one main control solution (physical, cultural, biological, chemical, monitoring and rotations) means that you can reduce herbicide use and still limit resistant weeds impact through management (M. Widderick , 2007; C. Preston, A. M. Wakelin, F. C. Dolman, Y. Bostamam and P. Boutsalis. 2009). Conclusion: Herbicide resistance in Australia is a large issue in agriculture with 38 resistant species, many of them are resistant to more than one herbicide mode of action.
Australia is the destination of the world’s most extreme examples of herbicide resistance through rye grass (L. rigidum), this weed along with others are negatively effecting crop yields. Many resistant weeds exhibit cross-resistance being very diverse and adaptable to a range of herbicides through mutations and selection which can be enhanced by poor farming techniques. The number of herbicide resistant species in Australia has been on the way up since 1982 and now in the 2010s more than ten species have become resistant compared to six in the 1980s. Understanding herbicide resistance through new technologies and new understandings will help to manage weeds better and limit their affect upon grain yields with the goal to reduce weed resistance in the
future.
My initial observation was that simple conservation actions such as reducing the use of pesticides can achieve measurable improvements in habitat quality and environmental health. Herbicides are toxic to most mammals as well as to the beneficial insects that you want to encourage in your garden. Sometimes herbicides seep into the ground water; causing contamination of which the long term effects are not known. Herbicide application can also result in drift or movement in the soil, this endangers wanted vegetation nearby. Herbicides are used far too rampantly. Excessive use of toxic herbicides is used when not necessary and because most are not aware of the many other natural alternatives. We must find more ways to cut back on the use of chemical herbicides and change to biological weed control methods.
In a good year all or most of them will thrive and give you wheat. But in a bad year a spate of high winds may take down the tallest stalks and leave standing at the harvest time only, say, the 10 percent of the crop that had a “shortness” gene. And if that wheat comprises your winter’s supply of bread, plus the only seed you’ll have for next year’s crop, then you’ll be almighty glad to have that small, short harvest. Genetic diversity, in domestic populations as well as wild ones, is nature’s sole insurance policy. Environments change: Wet years are followed by droughts, lakes dry up, volcanoes rumble, ice ages dawn. It’s a big, bad world out there for a little strand of DNA. But a population will persist over time if, deep within the scattered genetics of its ranks, it is literally prepared for anything. When the windy years persist for a decade, the wheat population will be overtaken by a preponderance of shortness, but if the crop maintains its diversity, there will always be recessive aspirations [i.e., recessive genes] for height hiding in there somewhere, waiting to have their day (97-98).
Kentucky blue grass has a V shaped or flat blade. The sides are parallel and the blade is smooth on both surfaces. There are 2 light lines astride the central vein and the tip is boat shaped. Rough blue grass has a flat blade 1-4 mm wide. The blade slightly tapers to a boat shaped tip. Both sides are smooth with a glossy abaxial surface. Light lines are not prominent and there is an onion skin appearance to the sheath base. Annual blue grass blades can be flat or V shaped and 2-3 mm wide. Parrellel sided or slightly tapering to a boat shaped tip and smooth on both sides. The blades are light green at both ends of the growing season and in winter. There are multiple light lines parallel to veins. It should be easy to distinguish between rough and annual blue grass by the lack of prominent light lines and glossy abaxial surface of rough blue grass and the multiple light lines and light green appearance of annual blue grass.
The pesticide DDT banned in 1987 was a detrimental to the environment leading to it to be banned in 1987. DDT remains in the soils for a long period of time. The chemicals affect the ecology of the soil and water run off causing contamination of livestock and native animals and aquatic species. Studies indicated a range of human health impacts from DDT including cancers, infertility, miscarriage and nervous system impairment. The social and economic impact of DDT use in viticulture was significant.
Since the birth of agriculture farmers across the world have been altering the genetic makeup of the crops they grow. Ancient farmers chose only the best looking plants and
Colony Collapse Disorder and Pesticides From around the year 2006, many bee farmers in the U.S.A and some parts of Europe started reporting sharp declines in their bee stocks. The reason for these declining numbers was not known and therefore scientists named it colony collapse disorder (CCD). Colony collapse disorder (CCD) is a not very old phenomenon and it became popular when large numbers of bee colonies started disappearing. The disappearance was mysterious since no dead bees were found in or around the beehives after a colony’s number was reported to have gone down or vanished.
In an article titled “The Threats From Genetically Modified Foods” by Robin Mather, he has said that the use of glyphosate, a herbicide, can “significantly increase the severity of various plant diseases” which is very hazardous to the environment. In the same article “The Threats From Genetically Modified Foods” Robin Mather has stated that genetic transfers cannot occur in nature and are not so precise and predictable as people say they are. In another article called “Biotechnology and Genetic Engineering” from Issues & Controversies, it has been shown that genetic modification can affect many plants. For instance, the article stated that In Oregon, there was genetically modified grass that had affected plants nearby which began to ruin all of the crops near the genetically modified
According to Approximately, 53% of the crops are engineered for herbicide tolerance, with another 33% for stacked traits, usually including herbicide tolerance. 14% are insect resistant using the Bt trait. Bacillus thurengiensis (Bt) is a spore forming bacterium that produces crystals protein, which are toxic to many species of insects. GM crops and their associated herbicides can harm birds, insects, amphibians, marine ecosystems, and soil organisms. They are reducing biodiversity, polluting water resources, and are making environments unsustainable for wildlife. A study published in Nature, one of the world’s leading scientific journals, has announced that Bt corn has contaminated indigenous varieties of corn tested in Oaxaca, Mexico. it was found that Bt corn destroyed the larvae of the monarch butterfly, raising well-grounded fears that many other natural plant and animal life may be impacted in the same way. It has been shown, however, that insects are fast developing resistance to Bt as well as to herbicides, resulting in even more massive infestation by the new superbugs. Despite GMOs crops being modified to be insect and herbicide resistant which increase our food supply nevertheless the modification done is harmful toward the
Nature practices diversity and for good reason. In nature and organic farming, if there is a threat to one species, there are others to balance the decrease in the threatened species. Conventional farmers and the modern food industry argue that planting the same crop year after year is convenient and profitable because it cuts down on the different types of farm equipment necessary in production, and initially, on the types of pesticides, herbicides, and fertilizers needed. However, in this unnatural environment, tremendous amounts of pesticides and fertilizers are needed to support crops as increased resistance occurs year after year (Pollan 72).... ...
As time has progressed, there has always been an overarching need for high amounts of crop production throughout the world. With the rapid rate of population growth, the need for crops and other sources of nutrients is only increasing. In order to meet these high demands and increase yields, farmers and other agriculturalists have started implementing the use of pesticides. These chemical mixtures are being used in order to prevent, destroy, repel or mitigate any pests from destroying growing crops. However, using pesticides on crops can create massive amounts of pollution, negatively affect an individual’s health, and can spark biodiversity loss within an ecosystem. According to Michael C.R. Alavanja, “Over 1 billion pounds of pesticides are used within the United States (US) each year and approximately 5.6 billion pounds are used worldwide”. With all this in mind, it is clear that pesticides should not be made available to farmers and agriculturalists, and should
Farming practices that do not use pesticides/herbicides are slowly becoming introduced bit biologically created pesticides are not nearly as productive as found in preliminary testing. Biotechnology has shown to have successfully resisted pests in plants that were destroyed by pesticides but still hasn’t proven itself as a better alternative. William Liebhardt Ph.D. is an Agricultural Specialist at the University of California, Davis and he says, “When you start spraying with pesticides, you disrupt the natural balance that exists in nature. As a result, you end up killing beneficial insects, then insects that were not a problem become problems and this happens repeatedly” requiring more and more spraying.
Frequency of application is defined as how often an insecticide is used that influence resistance development. Resistance can happen in many ways such as met...
The new chemicals which are produced to kill these strong pests and weeds may be more harmful to other plants and remove nutrients within the soil, in turn reducing the yield of agricultural crops. The benefits of these characteristics are seen in Argentina according to Pelletier (2010) as they use glyphosphate resistant soybean which allowed the comeback of this crop, as the soil was severely damaged from monoculture (The cultivation of a single crop in a defined area).... ... middle of paper ... ...
The pesticide is a controversial topic since farmers are used it to gain their yield. Especially, pesticide is discovered during World War II as a chemical weapon that mixture of multiple chemicals together to kill human. Therefore, Chantries redesign pesticide to kill an organism where and when we don’t want it. Because people want to go to the grocery store to buy the perfect product, pesticide makes it happens and with a little cost for farmers. Nonetheless, pesticide also is the expenditure of life expectancy, which directly threatens people and poses risk of mortality rate. Abusing the pesticide has multiple affects on our society, (Add). (Add thesis)