Benbrook, 2012
Benbrook, C, “Impacts of Genetically Engineered Crops on Pesticide Use in the U.S. – the First Sixteen Years,” Environmental Sciences-Europe, 2012, 24:24.
ABSTRACT:
BACKGROUND: Genetically engineered, herbicide-resistant and insect-resistant crops have been remarkable commercial successes in the United States. Few independent studies have calculated their impacts on pesticide use per hectare or overall pesticide use, or taken into account the impact of rapidly spreading glyphosate-resistant weeds. A model was developed to quantify by crop and year the impacts of six major transgenic pest-management traits on pesticide use in the U.S. over the 16-year period, 1996–2011: herbicide-resistant corn, soybeans, and cotton; Bacillus thuringiensis (Bt) corn targeting the European corn borer; Bt corn for corn rootworms; and Bt cotton for Lepidopteron insects.
RESULTS: Herbicide-resistant crop technology has led to a 239 million kilogram (527 million pound) increase in herbicide use in the United States between 1996 and 2011, while Bt crops have reduced insecticide applications by 56 million kilograms (123 million pounds). Overall, pesticide use increased by an estimated 183 million kgs (404 million pounds), or about 7%.
CONCLUSIONS: Contrary to often-repeated claims that today’s genetically-engineered crops have, and are reducing pesticide use, the spread of glyphosate-resistant weeds in herbicide-resistant weed management systems has brought about substantial increases in the number and volume of herbicides applied. If new genetically engineered forms of corn and soybeans tolerant of 2,4-D are approved, the volume of 2,4-D sprayed could drive herbicide usage upward by another approximate 50%. The magnitude of increases in herbicide use on herbicide-resistant hectares has dwarfed the reduction in insecticide use on Bt crops over the past 16 years, and will continue to do so for the foreseeable future. FULL TEXT
Lawton, 2017
Kurt Lawton, “Weed control outlook: Soybeans & corn,” Corn and Soybean Digest, February 7, 2017.
ABSTRACT: Not Available
See Hygeia Analytics Blog post about this article here: https://hygeia-analytics.com/2017/02/17/more-bad-news-on-the-resistant-weed-front/
Fisher et al., 2012
Madeline Fisher, “Many Little Hammers: Fighting Weed Resistance with Diversified Management,” 2012, Society of Agronomy Report, available online at: https://www.agronomy.org/files/publications/csa-news/many-little-hammers.pdf.
ABSTRACT:
Not Available
Davis et al., 2012
Adam S. Davis, Jason D. Hill, Craig A. Chase, Ann M. Johanns, and Matt Liebman, “Increasing Cropping System Diversity Balances Productivity, Profitability and Environmental Health,” PLoS One, 2012, 7:10, DOI: 10.1371/JOURNAL.PONE.0047149
ABSTRACT:
Balancing productivity, profitability, and environmental health is a key challenge for agricultural sustainability. Most crop production systems in the United States are characterized by low species and management diversity, high use of fossil energy and agrichemicals, and large negative impacts on the environment. We hypothesized that cropping system diversification would promote ecosystem services that would supplement, and eventually displace, synthetic external inputs used to maintain crop productivity. To test this, we conducted a field study from 2003–2011 in Iowa that included three contrasting systems varying in length of crop sequence and inputs. We compared a conventionally managed 2-yr rotation (maize-soybean) that received fertilizers and herbicides at rates comparable to those used on nearby farms with two more diverse cropping systems: a 3-yr rotation (maize-soybean-small grain + red clover) and a 4-yr rotation (maize-soybean-small grain + alfalfa-alfalfa) managed with lower synthetic N fertilizer and herbicide inputs and periodic applications of cattle manure. Grain yields, mass of harvested products, and profit in the more diverse systems were similar to, or greater than, those in the conventional system, despite reductions of agrichemical inputs. Weeds were suppressed effectively in all systems, but freshwater toxicity of the more diverse systems was two orders of magnitude lower than in the conventional system. Results of our study indicate that more diverse cropping systems can use small amounts of synthetic agrichemical inputs as powerful tools with which to tune, rather than drive, agroecosystem performance, while meeting or exceeding the performance of less diverse systems. FULL TEXT
Pleasants and Oberhauser, 2012
John M. Pleasants and Karen S. Oberhauser, “Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population,” Insect Conservation and Diversity, 2012, 6:2, DOI: 10.1111/J.1752-4598.2012.00196.X.
ABSTRACT:
1. The size of the Mexican overwintering population of monarch butter- flies has decreased over the last decade. Approximately half of these butterflies come from the U.S. Midwest where larvae feed on common milkweed. There has been a large decline in milkweed in agricultural fields in the Midwest over the last decade. This loss is coincident with the increased use of glyphosate herbicide in conjunction with increased planting of genetically modified (GM) glyphosate-tolerant corn (maize) and soybeans (soya).
2. We investigate whether the decline in the size of the overwintering population can be attributed to a decline in monarch production owing to a loss of milkweeds in agricultural fields in the Midwest. We estimate Midwest annual monarch production using data on the number of monarch eggs per milkweed plant for milkweeds in different habitats, the density of milkweeds in different habitats, and the area occupied by those habitats on the landscape.
3. We estimate that there has been a 58% decline in milkweeds on the Midwest landscape and an 81% decline in monarch production in the Midwest from 1999 to 2010. Monarch production in the Midwest each year was positively correlated with the size of the subsequent overwintering population in Mexico. Taken together, these results strongly suggest that a loss of agricultural milkweeds is a major contributor to the decline in the monarch population.
4. The smaller monarch population size that has become the norm will make the species more vulnerable to other conservation threats. FULL TEXT
Chang et al., 2011
Feng-chih Chang, Matt F. Simcik, Paul D. Capel, “Occurrence and fate of the herbicide glyphosate and its degradate aminomethylphosphonic acid in the atmosphere,” Environmental Toxicology and Chemistry, 2011, 30:3,
ABSTRACT:
This is the first report on the ambient levels of glyphosate, the most widely used herbicide in the United States, and its major degradation product, aminomethylphosphonic acid (AMPA), in air and rain. Concurrent, weekly integrated air particle and rain samples were collected during two growing seasons in agricultural areas in Mississippi and Iowa. Rain was also collected in Indiana in a preliminary phase of the study. The frequency of glyphosate detection ranged from 60 to 100% in both air and rain. The concentrations of glyphosate ranged from <0.01 to 9.1 ng/m3 and from <0.1 to 2.5 µg/L in air and rain samples, respectively. The frequency of detection and median and maximum concentrations of glyphosate in air were similar or greater to those of the other high-use herbicides observed in the Mississippi River basin, whereas its concentration in rain was greater than the other herbicides. It is not known what percentage of the applied glyphosate is introduced into the air, but it was estimated that up to 0.7% of application is removed from the air in rainfall. Glyphosate is efficiently removed from the air; it is estimated that an average of 97% of the glyphosate in the air is removed by a weekly rainfall ≥30 mm. FULL TEXT
Zobiole et al., 2010a
Luiz Henrique Saes Zobiole, Rubem Silvério de Oliveira Jr, Don Morgan Huber, Jamil Constantin, César de Castro, Fábio Alvares de Oliveira, Adilson de Oliveira Jr, “Glyphosate reduces shoot concentrations of mineral nutrients in glyphosate-resistant soybeans,” Plant and Soil, 2009, 328:1, DOI: 10.1007/s11104-009-0081-3.
ABSTRACT:
Although glyphosate-resistant (GR) technology is used in most countries producing soybeans (Glycine max L.), there are no particular fertilize recommendations for use of this technology, and not much has been reported on the influence of glyphosate on GR soybean nutrient status. An evaluation of different cultivar maturity groups on different soil types, revealed a significant decrease in macro and micronutrients in leaf tissues, and in photosynthetic parameters (chlorophyll, photosynthetic rate, transpiration and stomatal conductance) with glyphosate use (single or sequential application). Irrespective of glyphosate applications, concentrations of shoot macro- and micronutrients were found lower in the near-isogenic GR-cultivars compared to their respective non-GR parental lines Shoot and root dry biomass were reduced by glyphosate with all GR cultivars evaluated in both soils. The lower biomass in GR soybeans compared to their isogenic normal lines probably represents additive effects from the decreased photosynthetic parameters as well as lower availability of nutrients in tissues of the glyphosate treated plants. FULL TEXT
Gaines et al., 2010
Todd A. Gaines, Wenli Zhang, Dafu Wang, Bekir Bukun, Stephen T. Chisholm, Dale L. Shaner, Scott J. Nissen, William L. Patzoldt , Patrick J. Tranel , A. Stanley Culpepper , Timothy L. Grey , Theodore M. Webster , William K. Vencill, R. Douglas Sammons, Jiming Jiang, Christopher Prestoni, Jan E. Leacha, and Philip Westraa, “Gene amplification confers glyphosate resistance in Amaranthus palmeri,” PNAS, 2010, 107:3, DOI: 10.1073/PNAS/PNAS.0906649107.
ABSTRACT:
The herbicide glyphosate became widely used in the United States and other parts of the world after the commercialization of glyphosate-resistant crops. These crops have constitutive overexpression of a glyphosate-insensitive form of the herbicide target site gene, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Increased use of glyphosate over multiple years imposes selective genetic pressure on weed populations. We investigated recently discovered glyphosate-resistant Amaranthus palmeri populations from Georgia, in comparison with normally sensitive populations. EPSPS enzyme activity from resistant and susceptible plants was equally inhibited by glyphosate, which led us to use quantitative PCR to measure relative copy numbers of the EPSPS gene. Genomes of resistant plants contained from 5-fold to more than 160-fold more copies of the EPSPS gene than did genomes of susceptible plants. Quantitative RT-PCR on cDNA revealed that EPSPS expression was positively correlated with genomic EPSPS relative copy number. Immunoblot analyses showed that increased EPSPS protein level also correlated with EPSPS genomic copy number. EPSPS gene amplification was heritable, correlated with resistance in pseudo-F2 populations, and is proposed to be the molecular basis of glyphosate resistance. FISH revealed that EPSPS genes were present on every chromosome and, therefore, gene amplification was likely not caused by unequal chromosome crossing over. This occurrence of gene amplification as an herbicide resistance mechanism in a naturally occurring weed population is particularly significant because it could threaten the sustainable use of glyphosate-resistant crop technology. FULL TEXT
Eker et al., 2006
Selim Eker, Levent Ozturk, Atilla Yazici, Bulent Erenoglu, Volker Romheld, Ismail Cakmak, “Foliar-Applied Glyphosate Substantially Reduced Uptake and Transport of Iron and Manganese in Sunflower (Helianthus annuus L.) Plants,” Journal of Agricultural and Food Chemistry, 2006, DOI: 10.1021/JF0625196
ABSTRACT:
Evidence clearly shows that cationic micronutrients in spray solutions reduce the herbicidal effectiveness of glyphosate for weed control due to the formation of metal−glyphosate complexes. The formation of these glyphosate−metal complexes in plant tissue may also impair micronutrient nutrition of nontarget plants when exposed to glyphosate drift or glyphosate residues in soil. In the present study, the effects of simulated glyphosate drift on plant growth and uptake, translocation, and accumulation (tissue concentration) of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were investigated in sunflower (Helianthus annuus L.) plants grown in nutrient solution under controlled environmental conditions. Glyphosate was sprayed on plant shoots at different rates between 1.25 and 6.0% of the recommended dosage (i.e., 0.39 and 1.89 mM glyphosate isopropylamine salt). Glyphosate applications significantly decreased root and shoot dry matter production and chlorophyll concentrations of young leaves and shoot tips. The basal parts of the youngest leaves and shoot tips were severely chlorotic. These effects became apparent within 48 h after the glyphosate spray. Glyphosate also caused substantial decreases in leaf concentration of Fe and Mn while the concentration of Zn and Cu was less affected. In short-term uptake experiments with radiolabeled Fe (59Fe), Mn (54Mn), and Zn (65Zn), root uptake of 59Fe and 54Mn was significantly reduced in 12 and 24 h after application of 6% of the recommended dosage of glyphosate, respectively. Glyphosate resulted in almost complete inhibition of root-to-shoot translocation of 59Fe within 12 h and 54Mn within 24 h after application. These results suggest that glyphosate residues or drift may result in severe impairments in Fe and Mn nutrition of nontarget plants, possibly due to the formation of poorly soluble glyphosate−metal complexes in plant tissues and/or rhizosphere interactions. FULL TEXT
Anway et al., 2005
Anway, Matthew D., Cupp, Andrea S., Uzumcu, Mehmet, and Skinner, Michael K., “Epigenetic Transgenerational Actions of Endocrine Disruptors and Male Fertility,” Science, 2005, 308:5727, DOI: 10.1126/SCIENCE.1108190.
ABSTRACT:
Transgenerational effects of environmental toxins require either a chromosomal or epigenetic alteration in the germ line. Transient exposure of a gestating female rat during the period of gonadal sex determination to the endocrine disruptors vinclozolin (an antiandrogenic compound) or methoxychlor (an estrogenic compound) induced an adult phenotype in the F1 generation of decreased spermatogenic capacity (cell number and viability) and increased incidence of male infertility. These effects were transferred through the male germ line to nearly all males of all subsequent generations examined (that is, F1 to F4). The effects on reproduction correlate with altered DNA methylation patterns in the germ line. The ability of an environmental factor (for example, endocrine disruptor) to reprogram the germ line and to promote a transgenerational disease state has significant implications for evolutionary biology and disease etiology. FULL TEXT