Bibliography Tag: dicamba

Bohnenblust et al., 2016

Bohnenblust, E. W., Vaudo, A. D., Egan, J. F., Mortensen, D. A., & Tooker, J. F.; “Effects of the herbicide dicamba on nontarget plants and pollinator visitation;” Environmental Toxicology and Chemistry, 2016, 35(1), 144-151; DOI: 10.1002/etc.3169.

ABSTRACT:

Nearly 80% of all pesticides applied to row crops are herbicides, and these applications pose potentially significant ecotoxicological risks to nontarget plants and associated pollinators. In response to the widespread occurrence of weed species resistant to glyphosate, biotechnology companies have developed crops resistant to the synthetic-auxin herbicides dicamba and 2,4-dichlorophenoxyacetic acid (2,4-D); and once commercialized, adoption of these crops is likely to change herbicide-use patterns. Despite current limited use, dicamba and 2,4-D are often responsible for injury to nontarget plants; but effects of these herbicides on insect communities are poorly understood. To understand the influence of dicamba on pollinators, the authors applied several sublethal, drift-level rates of dicamba to alfalfa (Medicago sativa L.) and Eupatorium perfoliatum L. and evaluated plant flowering and floral visitation by pollinators. The authors found that dicamba doses simulating particle drift (≈1% of the field application rate) delayed onset of flowering and reduced the number of flowers of each plant species; however, plants that did flower produced similar-quality pollen in terms of protein concentrations. Further, plants affected by particle drift rates were visited less often by pollinators. Because plants exposed to sublethal levels of dicamba may produce fewer floral resources and be less frequently visited by pollinators, use of dicamba or other synthetic-auxin herbicides with widespread planting of herbicide-resistant crops will need to be carefully stewarded to prevent potential disturbances of plant and beneficial insect communities in agricultural landscapes. FULL TEXT


Oseland et al., 2020

Oseland, E., Bish, M., Steckel, L., & Bradley, K.; “Identification of environmental factors that influence the likelihood of off-target movement of dicamba;” Pest Management Science, 2020, 76(9), 3282-3291; DOI: 10.1002/ps.5887.

ABSTRACT:

BACKGROUND: Commercialization of dicamba-resistant soybean and cotton and subsequent post-emergence applications of dicamba contributed to at least 1.4 and 0.5 million hectares of dicamba-injured soybean in the United States in 2017 and 2018, respectively. This research was initiated to identify environmental factors that contribute to off-target dicamba movement. A survey was conducted following the 2017 growing season to collect information from dicamba applications that remained on the target field and those where dicamba moved. Weather and environmental data surrounding applications were collected and used to identify factors that reduce the likelihood of off-target movement. Soil pH was one factor identified in the model, and field experiments were conducted in 2018 and 2019 to validate the model. Three commercially-available dicamba formulations and one formulation currently in development were applied to soil at five distinct pH values. Sensitive soybean was used as a bioassay plant to detect dicamba volatilization.

RESULTS: Wind speeds the day of and following application, nearest water source to the field, soybean production acreage in the county, and soil pH were identified as factors that influence the likelihood for off-target movement. In the field study, when dicamba was applied to pH-adjusted soil and placed under low tunnels for 72 h, dicamba volatility increased when soil pH decreased as the model predicted. Dicamba choline, which is not commercially available, had reduced volatility compared to other formulations tested.

CONCLUSION: Results of this study identified specific factors that contribute to successful and unsuccessful dicamba applications and should be considered prior to applications.


Qi et al., 2020

Qi, M., Huo, J., Li, Z., He, C., Li, D., Wang, Y., Vasylieva, N., Zhang, J., & Hammock, B. D.; “On-spot quantitative analysis of dicamba in field waters using a lateral flow immunochromatographic strip with smartphone imaging;” Analytical and Bioanalytical Chemistry, 2020, 412(25), 6995-7006; DOI: 10.1007/s00216-020-02833-z.

ABSTRACT:

Dicamba herbicide is increasingly used in the world, in particular’ with the widespread cultivation of genetically modified dicamba-resistant crops. However, the drift problem in the field has caused phytotoxicity against naive, sensitive crops, raising legal concerns. Thus, it is particularly timely to develop a method that can be used for on-the-spot rapid detection of dicamba in the field. In this paper, a lateral flow immunochromatographic strip (LFIC) was developed. The quantitative detection can be conducted by an app on a smartphone, named “Color Snap.” The tool reported here provides results in 10 min and can detect dicamba in water with a LOD (detection limit) value of 0.1 mg/L. The developed LFIC shows excellent stability and sensitivity appropriate for field analysis. Our sensor is portable and excellent tool for on-site detection with smartphone imaging for better accuracy and precision of the results.


Riter et al., 2020


Riter, L. S., Sall, E. D., Pai, N., Beachum, C. E., & Orr, T. B.; “Quantifying Dicamba Volatility under Field Conditions: Part I, Methodology;” Journal of Agricultural and Food Chemistry, 2020, 68(8), 2277-2285; DOI: 10.1021/acs.jafc.9b06451.

ABSTRACT:

Quantitative assessment of the volatility of field applied herbicides requires orchestrated sampling logistics, robust analytical methods, and sophisticated modeling techniques. This manuscript describes a comprehensive system developed to measure dicamba volatility in an agricultural setting. Details about study design, sample collection, analytical chemistry, and flux modeling are described. A key component of the system is the interlaboratory validation of an analytical method for trace level detection (limit of quantitation of 1.0 ng/PUF) of dicamba in polyurethane foam (PUF) air samplers. Validation of field sampling and flux methodologies was conducted in a field trial that demonstrated agreement between predicted and directly measured dicamba air concentrations at a series of off-target locations. This validated system was applied to a field case study on two plots to demonstrate the utility of these methods under typical agricultural conditions. This case study resulted in a time-varying volatile flux profile, which showed that less than 0.2 +/- 0.05% of the applied dicamba was volatilized over the 3-day sampling period. FULL TEXT


Zhang et al., 2019b

Zhang, J., Huang, Y., Reddy, K. N., & Wang, B.; “Assessing crop damage from dicamba on non-dicamba-tolerant soybean by hyperspectral imaging through machine learning;” Pest Management Science, 2019, 75(12), 3260-3272; DOI: 10.1002/ps.5448.

ABSTRACT:

BACKGROUND: Dicamba effectively controls several broadleaf weeds. The off-target drift of dicamba spray or vapor drift can cause severe injury to susceptible crops, including non-dicamba-tolerant crops. In a field experiment, advanced hyperspectral imaging (HSI) was used to study the spectral response of soybean plants to different dicamba rates, and appropriate spectral features and models for assessing the crop damage from dicamba were developed.

RESULTS: In an experiment with six different dicamba rates, an ordinal spectral variation pattern was observed at both 1 week after treatment (WAT) and 3 WAT. The soybean receiving a dicamba rate >/=0.2X exhibited unrecoverable damage. Two recoverability spectral indices (HDRI and HDNI) were developed based on three optimal wavebands. Based on the Jeffries-Matusita distance metric, Spearman correlation analysis and independent t-test for sensitivity to dicamba spray rates, a number of wavebands and classic spectral features were extracted. The models for quantifying dicamba spray levels were established using the machine learning algorithms of naive Bayes, random forest and support vector machine.

CONCLUSIONS: The spectral response of soybean injury caused by dicamba sprays can be clearly captured by HSI. The recoverability spectral indices developed were able to accurately differentiate the recoverable and unrecoverable damage, with an overall accuracy (OA) higher than 90%. The optimal spectral feature sets were identified for characterizing dicamba spray rates under recoverable and unrecoverable situations. The spectral features plus plant height can yield relatively high accuracy under the recoverable situation (OA = 94%). These results can be of practical importance in weed management. (c) 2019 Society of Chemical Industry.

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Soltani et al., 2020

Soltani, Nader, Oliveira, Maxwel C., Alves, Guilherme S., Werle, Rodrigo, Norsworthy, Jason K., Sprague, Christy L., Young, Bryan G., Reynolds, Daniel B., Brown, Ashli, & Sikkema, Peter H.; “Off-target movement assessment of dicamba in North America;” Weed Technology, 2020, 34(3), 318-330; DOI: 10.1017/wet.2020.17.

ABSTRACT:

Six experiments were conducted in 2018 on field sites located in Arkansas, Indiana, Michigan, Nebraska, Ontario, and Wisconsin to evaluate the off-target movement (OTM) of dicamba under field-scale conditions. The highest estimated dicamba injury in non-dicamba-resistant (DR) soybean was 50, 44, 39, 67, 15, and 44% injury for non-covered areas and 59, 5, 13, 42, 0, and 41% injury for covered areas during dicamba application in Arkansas, Indiana, Michigan, Nebraska, Ontario, and Wisconsin, respectively. The level of injury generally decreased exponentially as the downwind distance increased under covered and non-covered areas at all sites. There was an estimated 10% injury in non-DR soybean at 113, 8, 11, 8, and 8 m; and estimated 1% injury at 293, 28, 71, 15, and 19 m from the edge of treated field downwind when plants were not covered during dicamba application in Arkansas, Indiana, Michigan, Ontario and Wisconsin, respectively. Filter paper collectors placed from 4 up to 137 m downwind from the edge of the sprayed area suggested that the dicamba deposition reduced exponentially with distance. The greatest injury to non-DR soybean from dicamba OTM occurred at Nebraska and Arkansas (as far as 250 m). Non-DR soybean injury was greatest adjacent to the dicamba sprayed area but, injury decreased with no injury beyond 20 m downwind or any other direction from the dicamba sprayed area in Indiana, Michigan, Ontario, and Wisconsin. The presence of soybean injury under covered and non-covered areas during the spray period for primary drift suggests that secondary movement of dicamba was evident at five sites. Further research is needed to determine the exact forms of secondary movement of dicamba under different environmental conditions. FULL TEXT


Christensen et al., 2016

Christensen, C. H., Barry, K. H., Andreotti, G., Alavanja, M. C., Cook, M. B., Kelly, S. P., Burdett, L. A., Yeager, M., Beane Freeman, L. E., Berndt, S. I., & Koutros, S.; “Sex Steroid Hormone Single-Nucleotide Polymorphisms, Pesticide Use, and the Risk of Prostate Cancer: A Nested Case-Control Study within the Agricultural Health Study;” Frontiers in Oncology, 2016, 6, 237; DOI: 10.3389/fonc.2016.00237.

ABSTRACT:

Experimental and epidemiologic investigations suggest that certain pesticides may alter sex steroid hormone synthesis, metabolism or regulation, and the risk of hormone-related cancers. Here, we evaluated whether single-nucleotide polymorphisms (SNPs) involved in hormone homeostasis alter the effect of pesticide exposure on prostate cancer risk. We evaluated pesticide-SNP interactions between 39 pesticides and SNPs with respect to prostate cancer among 776 cases and 1,444 controls nested in the Agricultural Health Study cohort. In these interactions, we included candidate SNPs involved in hormone synthesis, metabolism or regulation (N = 1,100), as well as SNPs associated with circulating sex steroid concentrations, as identified by genome-wide association studies (N = 17). Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Multiplicative SNP-pesticide interactions were calculated using a likelihood ratio test. We translated p-values for interaction into q-values, which reflected the false discovery rate, to account for multiple comparisons. We observed a significant interaction, which was robust to multiple comparison testing, between the herbicide dicamba and rs8192166 in the testosterone metabolizing gene SRD5A1 (p-interaction = 4.0 x 10(-5); q-value = 0.03), such that men with two copies of the wild-type genotype CC had a reduced risk of prostate cancer associated with low use of dicamba (OR = 0.62 95% CI: 0.41, 0.93) and high use of dicamba (OR = 0.44, 95% CI: 0.29, 0.68), compared to those who reported no use of dicamba; in contrast, there was no significant association between dicamba and prostate cancer among those carrying one or two copies of the variant T allele at rs8192166. In addition, interactions between two organophosphate insecticides and SNPs related to estradiol metabolism were observed to result in an increased risk of prostate cancer. While replication is needed, these data suggest both agonistic and antagonistic effects on circulating hormones, due to the combination of exposure to pesticides and genetic susceptibility, may impact prostate cancer risk. FULL TEXT


Lerro et al., 2020

Lerro, C. C., Hofmann, J. N., Andreotti, G., Koutros, S., Parks, C. G., Blair, A., Albert, P. S., Lubin, J. H., Sandler, D. P., & Beane Freeman, L. E.; “Dicamba use and cancer incidence in the agricultural health study: an updated analysis;” International Journal of Epidemiology, 2020; DOI: 10.1093/ije/dyaa066.

ABSTRACT:

BACKGROUND: The herbicide dicamba has been commonly used agriculturally and residentially. Recent approval of genetically engineered dicamba-resistant crops is expected to lead to increased dicamba use, and there has been growing interest in potential human health effects. A prior analysis in the Agricultural Health Study (AHS) suggested associations between dicamba and colon and lung cancer. We re-evaluated dicamba use in the AHS, including an additional 12 years and 2702 exposed cancers.

METHODS: The AHS is a prospective cohort of pesticide applicators in Iowa and North Carolina. At enrollment (1993–1997) and follow-up (1999–2005), participants reported dicamba use. Exposure was characterized by cumulative intensity-weighted lifetime days, including exposure lags of up to 20 years. We estimated relative risks (RR) and 95% confidence intervals (CI) using multivariable Poisson regression for incident cancers diagnosed from enrollment through 2014/2015.

RESULTS: Among 49 922 applicators, 26 412 (52.9%) used dicamba. Compared with applicators reporting no dicamba use, those in the highest quartile of exposure had elevated risk of liver and intrahepatic bile duct cancer (nexposed = 28, RRQ4 = 1.80, CI: 1.26–2.56, Ptrend < 0.001) and chronic lymphocytic leukaemia (CLL, nexposed = 93, RRQ4 = 1.20, CI: 0.96–1.50, Ptrend = 0.01) and decreased risk of myeloid leukaemia (nexposed = 55, RRQ4 = 0.73, CI: 0.51–1.03, Ptrend = 0.01). The associations for liver cancer and myeloid leukaemia remained after lagging exposure of up to 20 years.

CONCLUSIONS: With additional follow-up and exposure information, associations with lung and colon cancer were no longer apparent. In this first evaluation of liver and intrahepatic bile duct cancer, there was an association with increasing use of dicamba that persisted across lags of up to 20 years. FULL TEXT


Gage et al., 2019

Gage, Karla L., Krausz, Ronald F., & Walters, S. Alan; “Emerging Challenges for Weed Management in Herbicide-Resistant Crops;” Agriculture, 2019, 9(8); DOI: 10.3390/agriculture9080180.

ABSTRACT:

Since weed management is such a critical component of agronomic crop production systems, herbicides are widely used to provide weed control to ensure that yields are maximized. In the last few years, herbicide-resistant (HR) crops, particularly those that are glyphosate-resistant, and more recently, those with dicamba (3,6-dichloro-2-methoxybenzoic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) resistance are changing the way many growers manage weeds. However, past reliance on glyphosate and mistakes made in stewardship of the glyphosate-resistant cropping systemhave directly led to the current weed resistance problems that now occur in many agronomic cropping systems, and new technologies must be well-stewarded. New herbicide-resistant trait technologies in soybean, such as dicamba-, 2,4-D-, and isoxaflutole- ((5-cyclopropyl-4-isoxazolyl)[2-(methylsulfonyl)-4-(trifluoromethyl)phenyl]methanone) resistance, are being combined with glyphosate- and glufosinate-resistance traits to manage herbicide-resistant weed populations. In cropping systems with glyphosate-resistant weed species, these new trait options may provide effective weed management tools, although there may be increased risk of off-target movement and susceptible plant damage with the use of some of these technologies. The use of diverse weed management practices to reduce the selection pressure for herbicide-resistant weed evolution is essential to preserve the utility of new traits. The use of herbicides with differing sites of action (SOAs), ideally in combination as mixtures, but also in rotation as part of a weed management program may slow the evolution of resistance in some cases. Increased selection pressure from the effects of some herbicide mixtures may lead to more cases of metabolic herbicide resistance. The most effective long-term approach for weed resistance management is the use of Integrated Weed Management (IWM) which may build the ecological complexity of the cropping system. Given the challenges in management of herbicide-resistant weeds, IWM will likely play a critical role in enhancing future food security for a growing global population. FULL TEXT


Dellaferrera et al., 2018

Dellaferrera, Ignacio, Cortés, Eduardo, Panigo, Elisa, De Prado, Rafael, Christoffoleti, Pedro, & Perreta, Mariel, “First Report of Amaranthus hybridus with Multiple Resistance to 2,4-D, Dicamba, and Glyphosate,” Agronomy, 2018, 8(8). DOI: 10.3390/agronomy8080140.

ABSTRACT:

In many countries, Amaranthus hybridus is a widespread weed in agricultural systems. The high prolificacy and invasive capacity as well as the resistance of some biotypes to herbicides are among the complications of handling this weed. This paper reports on the first A. hybridus biotypes with resistance to auxinic herbicides and multiple resistance to auxinic herbicides and the EPSPs inhibitor, glyphosate. Several dose response assays were carried out to determine and compare sensitivity of six population of A. hybridus to glyphosate, 2,4-D, and dicamba. In addition, shikimic acid accumulation and piperonil butoxide effects on 2,4-D and dicamba metabolism were tested in the same populations. The results showed four populations were resistant to dicamba and three of these were also resistant to 2,4-D, while only one population was resistant to glyphosate. The glyphosate-resistant population also showed multiple resistance to auxinic herbicides. Pretreatment with piperonil butoxide (PBO) followed by 2,4-D or dicamba resulted in the death of all individual weeds independent of herbicide or population. FULL TEXT