Nowell et al., 2018

Nowell Lisa H., Moran Patrick W., Schmidt Travis S., Norman Julia E., Nakagaki Naomi, Shoda Megan E., Mahler Barbara J., Van Metre Peter C., Stone Wesley W., Sandstrom Mark W., Hladik Michelle L., “Complex mixtures of dissolved pesticides show potential aquatic toxicity in a synoptic study of Midwestern U.S. streams,” Science of the Total Environment, 613-614, 2018, DOI: 10.1016/j.scitotenv.2017.06.156

ABSTRACT:

Aquatic organisms in streams are exposed to pesticide mixtures that vary in composition over time in response to changes in flow conditions, pesticide inputs to the stream, and pesticide fate and degradation within the stream. To characterize mixtures of dissolved-phase pesticides and degradates in Midwestern streams, a synoptic study was conducted at 100 streams during May–August 2013. In weekly water samples, 94 pesticides and 89 degradates were detected, with a median of 25 compounds detected per sample and 54 detected per site. In a screening-level assessment using aquatic-life benchmarks and the Pesticide Toxicity Index (PTI), potential effects on fish were unlikely in most streams. For invertebrates, potential chronic toxicity was predicted in 53% of streams, punctuated in 12% of streams by acutely toxic exposures. For aquatic plants, acute but likely reversible effects on biomass were predicted in 75% of streams, with potential longer-term effects on plant communities in 9% of streams. Relatively few pesticides in water—atrazine, acetochlor, metolachlor, imidacloprid, fipronil, organophosphate insecticides, and carbendazim—were predicted to be major contributors to potential toxicity. Agricultural streams had the highest potential for effects on plants, especially in May–June, corresponding to high spring-flush herbicide concentrations. Urban streams had higher detection frequencies and concentrations of insecticides and most fungicides than in agricultural streams, and higher potential for invertebrate toxicity, which peaked during July–August. Toxicity-screening predictions for invertebrates were supported by quantile regressions showing significant associations for the Benthic Invertebrate-PTI and imidacloprid concentrations with invertebrate community metrics for MSQA streams, and by mesocosm toxicity testing with imidacloprid showing effects on invertebrate communities at environmentally relevant concentrations. This study documents the most complex pesticide mixtures yet reported in discrete water samples in the U.S. and, using multiple lines of evidence, predicts that pesticides were potentially toxic to nontarget aquatic life in about half of the sampled streams.  FULL TEXT

Stone et al., 2014

Wesley A. Stone, Robert J,. Gillom, and Karen R. Ryberg, “Pesticides in U.S. Streams and Rivers: Occurrence and Trends during 1992−2011,” Environmental Science & Technology, 2014, 48, DOI: 10.1021/es5025367

ABSTRACT:

During the 20 years from 1992 to 2011, pesticides were found at concentrations that exceeded aquatic-life benchmarks in many rivers and streams that drain agricultural, urban, and mixed-land use watersheds. Overall, the proportions of assessed streams with one or more pesticides that exceeded an aquatic life benchmark were very similar between the two decades for agricultural (69% during 1992−2001 compared to 61% during 2002−2011) and mixed-land-use streams (45% compared to 46%). Urban streams, in contrast, increased from 53% during 1992−2011 to 90% during 2002−2011, largely because of fipronil and dichlorvos. The potential for adverse effects on aquatic life is likely greater than these results indicate because potentially important pesticide compounds were not included in the assessment. Human-health benchmarks were much less frequently exceeded, and during 2002−2011, only one agricultural stream and no urban or mixed-land-use streams exceeded human-health benchmarks for any of the measured pesticides. Widespread trends in pesticide concentrations, some downward and some upward, occurred in response to shifts in use patterns primarily driven by regulatory changes and introductions of new pesticides. FULL TEXT

Westerman et al., 2005

Paula R. Westerman, Matt Liebman, Fabián D. Menalled, Andrew H. Heggenstaller, Robert G. Hartzler, Philip M. Dixon, “Are many little hammers effective? Velvetleaf (Abutilon theophrasti) population dynamics in two- and four-year crop rotation systems,” Weed Science, 53, 2005.

ABSTRACT:

Liebman, 2017

Matt Liebman, “Cultural techniques to manage weeds,” in Integrated weed management for sustainable agriculture, Ed: Robert Zimdahl, 2017, Burleigh Dodds Science Publishing.

SUMMARY:

The focus of this chapter is on cultural techniques that can also contribute to effective weed management strategies, including choice of crop density, crop arrangement, and crop genotype, and manipulation of initial crop size, soil fertility, and soil moisture conditions. Weed management strategies that make use of cultural factors seek to reduce weed density, resource consumption, biomass production and competition with crops. They also seek to prevent colonization of fields by weed species not previously present. Additionally, by altering the availability of light, water and nutrients in space and time, and by challenging weeds with allelochemicals, cultural tactics are intended to improve crop performance. FULL TEXT

Liebman and Gallandt, 1997

Matt Liebman and Eric Gallandt, “Many Little Hammers: Ecological Management of Crop-Weed Interactions,” In Ecology and Agriculture,” Ed: L.E. Jackson, 1997, Academic Press.

SUMMARY:

This is the first introduction of the phrase “many little hammers” to describe what is now known as integrated weed management, or IWM.  IWM relies on using a diverse assortment of weed control methods, possibly along with some herbicide use, along with changes in crop density and rotation to achieve weed control.  FULL TEXT

Liebman and Davis, 2009

Matt Liebman and Adam Davis, “Managing Weeds in Organic Farming Systems: An Ecological Approach,” In Organic Farming: The Ecological System, Ed: Charles Francis, 2009.

SUMMARY:

In this chapter, we describe major components of the weed management tool kit for organic farming, highlighting areas in which important advances have been made in the last decade. We then argue that instead of approaching the development of multitactic weed management strategies as a purely empirical, trial-and-error activity, the choice and deployment of weed management tactics should instead be informed by insights from ecological theory… Finally, we emphasize the need for ongoing dialog between empiricists and theoreticians and between scientists and farmers, so as to better direct scarce research resources and management time to where they are likely to be most beneficial. Multitactic weed management strategies informed by theory should be useful not just to organic farmers but also to conventional farmers who seek to reduce their reliance on herbicides due to concerns over herbicide resistance in weeds, rising production costs, and environmental and human health risks associated with herbicide exposure. FULL TEXT

Landrigan, 2018

Philip J. Landrigan, “Pesticides and Human Reproduction,” JAMA Internal Medicine, 2018, 178:1, DOI:10.1001/jamainternmed.2017.5092

SUMMARY:

Invited commentary by Managing Weeds for Healthy Kids science team member Dr. Landrigan reports that herbicide use has increased sharply, with glyphosate use up 250-fold from 1974 to 2014.  And, “measurable levels of multiple pesticides are found in the bodies of nearly all Americans…and pesticides are capable of causing a wide range of asymptomatic effects at levels of exposure too low to produce overt signs and symptoms.”  New theories suggest that long term exposure to pesticides cause this kind of subclinical toxicity.  Dr. Landrigan reviews the known linkages, including in utero chlorpyrifos exposure leading to neurodevelopmental deficits, and reproductive injury including adverse birth outcomes and birth defects. He recommends: “We need to overcome the strident objections of the pesticide manufacturing industry, recognize the hidden costs of deregulation, and strengthen requirements for both premarket testing of new pesticides, as well as postmarketing surveillance of exposed populations— exactly as we do for another class of potent, biologically active molecules—drugs.”  FULL TEXT

Laugeray et al., 2014

Anthony Laugeray, Ameziane Herzine, Olivier Perche,1,2 Betty Hébert, Marine Aguillon-Naury, Olivier Richard, Arnaud Menuet, Séverine Mazaud-Guittot, Laurianne Lesné, Sylvain Briault, Bernard Jegou, Jacques Pichon, Céline Montécot-Dubourg, and Stéphane Mortaud, “Pre- and Postnatal Exposure to Low Dose Glufosinate Ammonium Induces Autism-Like Phenotypes in Mice,” Frontiers in Behavioral Neuroscience, 2014, 8:390, DOI: 10.3389/fnbeh.2014.00390

ABSTRACT:

Glufosinate ammonium (GLA) is one of the most widely used herbicides in agriculture. As is the case for most pesticides, potential adverse effects of GLA have not been studied from the perspective of developmental neurotoxicity. Early pesticides exposure may weaken the basic structure of the developing brain and cause permanent changes leading to a wide range of lifelong effects on health and/or behavior. Here, we addressed the developmental impact of GLA by exposing female mice to low dose GLA during both pre- and postnatal periods and analyzed potential developmental and behavioral changes of the offspring during infancy and adulthood. A neurobehavioral test battery revealed significant effects of GLA maternal exposure on early reflex development, pup communication, affiliative behaviors, and preference for social olfactory cues, but emotional reactivity and emotional memory remained unaltered. These behavioral alterations showed a striking resemblance to changes seen in animal models of Autistic Spectrum Disorders. At the brain level, GLA maternal exposure caused some increase in relative brain weight of the offspring. In addition, reduced expression of Pten and Peg3 – two genes implicated in autism-like deficits – was observed in the brain of GLA-exposed pups at postnatal day 15. Our work thus provides new data on the link between pre- and postnatal exposure to the herbicide GLA and the onset of autism-like symptoms later in life. It also raises fundamental concerns about the ability of current safety testing to assess risks of pesticide exposure during critical developmental periods.  FULL TEXT

McDuffie et al., 2001

Helen H. McDuffie, Punam Pahwa, John R. McLaughlin, John J. Spinelli, Shirley Fincham, James A. Dosman, Diane Robson, Leo F. Skinnider and Norman W. Choi, “Non-Hodgkin’s Lymphoma and Specific Pesticide Exposures in Men: Cross-Canada Study of Pesticides and Health,” Cancer Epidemiology, Biomarkers, & Prevention, 2001, 10.

ABSTRACT:

Our objective in the study was to investigate the putative associations of specific pesticides with non-Hodgkin’s Lymphoma [NHL; International Classification of Diseases, version 9 (ICD-9) 200, 202]. We conducted a Canadian multicenter population-based incident, case (n = 517)-control (n = 1506) study among men in a diversity of occupations using an initial postal questionnaire followed by a telephone interview for those reporting pesticide exposure of 10 h/year or more, and a 15% random sample of the remainder. Adjusted odds ratios (ORs) were computed using conditional logistic regression stratified by the matching variables of age and province of residence, and subsequently adjusted for statistically significant medical variables (history of measles, mumps, cancer, allergy desensitization treatment, and a positive history of cancer in first-degree relatives). We found that among major chemical classes of herbicides, the risk of NHL was statistically significantly increased by exposure to phenoxyherbicides [OR, 1.38; 95% confidence interval (CI), 1.06–1.81] and to dicamba (OR, 1.88; 95% CI, 1.32–2.68). Exposure to carbamate (OR, 1.92; 95% CI, 1.22–3.04) and to organophosphorus insecticides (OR, 1.73; 95% CI, 1.27–2.36), amide fungicides, and the fumigant carbon tetrachloride (OR, 2.42; 95% CI, 1.19–5.14) statistically significantly increased risk. Among individual compounds, in multivariate analyses, the risk of NHL was statistically significantly increased by exposure to the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D; OR, 1.32; 95% CI, 1.01–1.73), mecoprop (OR, 2.33; 95% CI, 1.58–3.44), and dicamba (OR, 1.68; 95% CI, 1.00–2.81); to the insecticides malathion (OR, 1.83; 95% CI, 1.31–2.55), 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT), carbaryl (OR, 2.11; 95% CI, 1.21–3.69), aldrin, and lindane; and to the fungicides captan and sulfur compounds. In additional multivariate models, which included exposure to other major chemical classes or individual pesticides, personal antecedent cancer, a history of cancer among first-degree relatives, and exposure to mixtures containing dicamba (OR, 1.96; 95% CI, 1.40–2.75) or to mecoprop (OR, 2.22; 95% CI, 1.49–3.29) and to aldrin (OR, 3.42; 95% CI, 1.18–9.95) were significant independent predictors of an increased risk for NHL, whereas a personal history of measles and of allergy desensitization treatments lowered the risk. We concluded that NHL was associated with specific pesticides after adjustment for other independent predictors. FULL TEXT

Steckel, 2012

Larry Steckel, “Glyphosate-Resistant Weeds: Lessons Learned in Tennessee,” Presentation to the Iowa Soybean Association, On-Farm Network Conference, Ames, IA, February 16, 2012

SUMMARY:

Describes aggressive spread of glyphosate reisistant weeds and the importance of proactive management, including prevention and early detection and recommends herbicide protocols to control weeds. FULL TEXT