Brief Summary of Minutes of Annual Meeting

Accomplishments

Objective 1:  Characterize abiotic and biotic reaction mechanisms, transformation rates, and fate in agricultural and natural ecosystems.

Lousiana, Amrbrust. Shallow water aquatic systems are relevant to many areas in agriculture.  Some agricultural settings, such as rice culture, make use of these directly to control weeds and other agricultural pests.  They are also employed in aquaculture for many marine species (fish, crabs, shrimp) as well as freshwater aquaculture (catfish, crawfish) and can serve as breeding grounds freshwater and marine organisms and serve as breeding grounds for juvenile organisms.  Intertidal estuarine systems at the terminus of agricultural watersheds and near shore waterbodies receiving agricultural runoff are also relevant habitats.  Environmental fate processes that occur within these areas may dominate in comparison to processes in deeper water bodies.  For example, photochemical processes will be more dominant in shallow water versus deeper water bodies where light is more strongly attenuated.  Additionally, photochemical processes at sediment-water interfaces can become significant in these ecosystems and can include not only degradation through direct photochemical processes but also indirect processes at the interface or thought radical oxidants generated at the interface.  Additionally organisms that live within these habitats may be more susceptible to photochemically induced toxicity.  This may occur through direct absorption of a chemical from the water or, for epibenthic organisms, exposure to the pore water at the sediment water interface.  The purpose of the present and ongoing investigation was to apply shallow irradiated water-sediments systems to simulate degradation processes influenced by sunlight in shallow aquatic habitats to the new rice herbicide Benzobicylon (RougeÒ) and measure its degradation in rice field settings.  Results from this work can assist growers with dissipation information under local conditions as well as provide data allowing more informed exposure assessments by the US EPA.

Montana, Sterling. Smooth brome volatiles may help trap a major insect pest of wheat. Smooth brome (Bromus inermis Leyss.) is a cool-season, perennial grass that spreads by rhizomes and was introduced in the 1880s as a livestock forage and for erosion control; it grows across North America along most highways and many times in proximity to wheat-growing regions, and is considered weedy in some habitats.  The major wheat pest, wheat stem sawfly (Cephus cinctus Norton) (WSS) causes $350 million of annual damage in wheat fields throughout the Northern Great Plains. Insecticides are not effective in this pest system, but smooth brome may be an alternate host and serve as a perimeter trap. No data exist to demonstrate its effectiveness; therefore, we investigated host preference behaviors of WSS between plants at two growth stages in laboratory and greenhouse conditions and identified and quantified attractive volatile compounds from wheat and smooth brome using GC-MS. In Y- tube olfactometer bioassay, WSS were more attracted towards the volatiles emitted from bromes compared to wheat. Furthermore, the duration of oviposition insertion along with the length of time spent on stem, leaves, oviposition insertions, and quiescence was higher in brome as compared to wheat (data not shown). There were more eggs per stem in bromes than in wheat. Consistent with these behaviors, we found significant differences in some volatile compounds collected from both plant species among which some of them have been suggested as behaviorally active compound for female WSS. With more egg loads and more larval mortality in premature stages of plants, less cut stems and significantly higher amount of behaviorally active volatile compounds, smooth bromes could potentially be used to improve integrated pest management strategies for WSS.

Objectives: 1. Characterize abiotic and biotic reaction mechanisms, transformation rates, and fate in agricultural and natural ecosystems, and 2. Determine adverse impacts from agrochemical exposure to cells, organisms, and ecosystems.

Ohio, Michal. Phragmites Composting: Optimization of Compost Amendment Ratio and Determination of Seed and Glyphosate Persistence. Phragmites (Phragmites australis subspecies australis) is an invasive, non-native reed grass that has inundated natural areas of Ohio and the United States. Certain natural and restored areas along the Black River near Lorain, Ohio have become overgrown with Phragmites over many years. Phragmites is one of the fastest growing and most invasive grass species. Controlling Phragmites infestations usually requires multiple herbicide applications during the spring or summer after panicle formation (Mozdzer et al., 2008), followed by cutting the plants at ground level for disposal. The herbicide used to kill Phragmites is Aqua-net, an aquatic glyphosate with a non-ionic surfactant. Glyphosate containing herbicides are widely used and also known by the trade names Rodeo, Roundup and Shore Klear. A question that has been raised concerning the use of these herbicides is whether they would persist and be present at phytotoxic concentrations in composts produced from treated Phragmites residues. This is of concern since nearly all of the Phragmites removed from the site may have received a lethal dose of glyphosate.

Nebraska, Snow. Mechanisms, mitigation and uptake of geogenic contaminants in ephemerally irrigated crops. This four-year study is focused on transfer of arsenic, uranium and selenium from soil or irrigation water to food and feed crops and will improve our understanding of the fate of these chemicals in the environment as well as their impacts to humans and animals. Results to date help characterize conditions under which uranium, selenium and arsenic is taken up from irrigation water at different stages of plant development.  Field sites in western and central Nebraska have been monitored using soil cores, lysimeters and plant tissue samples over a two growing seasons.  One growing season of greenhouse experiments designed to test the importance of ferrihydrite suggests that transformation and redox cycling of iron oxyhydroxides is one of the key processes affecting mobility and bioavailability of these elements. Crop uptake of arsenic, uranium and selenium is correlated with mobile forms of these elements in soil porewater.

Objectives: 1. Characterize abiotic and biotic reaction mechanisms, transformation rates, and fate in agricultural and natural ecosystems, 2. Determine adverse impacts from agrochemical exposure to cells, organisms, and ecosystems, and 3. Develop technologies that mitigate adverse human and environmental impacts.

Oregon, Jenkins. Probabilistic Methods to Investigate the Fate of Chlorpyrifos and Chlorpyrifos-oxon at the Watershed Scale. Pacific Northwest freshwater resources are key elements in the life history and ecology of Pacific salmon and steelhead (Oncorhynchus sp.). In addition to overfishing, critical habit degradation and loss has been identified as contributing to population decline, resulting in 28 evolutionarily significant units (ESUs) listed as threatened or endangered under the Endangered Species Act (ESA). Characterizing risks to Pacific salmonids and their food web related to pesticide exposure requires complex spatial and temporal information on life history and ecology, as well as pesticide use patterns and environmental fate. For this study, a probabilistic approach is used to characterize use practices of the organophosphate insecticide chlorpyrifos in the Zollner Creek watershed located in the Willamette Valley of Oregon between 2010 and 2011. The Soil and Water Assessment Tool (SWAT) will be used to simulate the fate and transport of chlorpyrifos and its oxon degradate in the watershed in order to estimate aqueous exposure concentrations over a continuous 2 year period.

California, Gan. A Novel Water-Swelling Sampling Probe for in vivo Detection of Neonicotinoids in Plants. Neonicotinoids have rapidly become one of the most commonly used insecticides since their initial introduction in 1990s. The extensive use of neonicotinoids has led to increasing concerns over their adverse ecological implications. Of these concerns, the worldwide crisis of pollinator colonies is regarded as the most urgent. Even though there has been extensive research on the potential role of neonicotinoids in pollinator population declines, limitations in sampling and analytical techniques are preventing a mechanistic understanding to directly connect exposure to the adverse consequence. Most studies to date rely on correlation of the presence of neonicotinoid residues in plant materials with toxicity effects in exposed pollinators or their communities. Conventional analytical methods operate on the principle of exhaustive extraction and analysis of total chemical concentrations. The uptake and translocation of systemic pesticides such as neonicotinoids in plants is via the transpiration stream in xylem, while their distribution in sugars occurs through phloem. Therefore, for pollinators, quantification of neonicotinoids in nectar and sap of flowering plants would improve the estimation of chemical exposure. We developed a sensitive biomimetic SPME fiber for detecting seven neonicotinoids in live plants. The fiber was fabricated by assembling water-swelling crosslinked polyvinyl-pyrrolidone particles on a stainless-steel wire via a simple dip-coating step, and the surface coating was then modified by oxidative self-polymerization of norepinephrine to obtain biocompatible and anti-fouling properties. We demonstrated that the in vivo SPME probe provided nearly instantaneous measurement of neonicotinoids in sap, and that when coupled with the analysis of total tissue concentrations, offered insights on the distribution of neonicotinoids between plant sap and tissue matter.

Objectives: 3. Determine adverse impacts from agrochemical exposure to cells, organisms, and ecosystems, and 4. Develop technologies that mitigate adverse human and environmental impacts.

Hawaii, Li. Putative mode of action of the monoterpenoids linalool, estragole, methyl eugenol and citronellal on ligand-gated ion channels. Essential oils have been used as sedatives, anticonvulsants and local anesthetics in traditional medical remedies; preservatives for food, fruit, vegetable; and grain storage and bio-pesticides for food production. Linalool, along with a few other major components such as estragole, methyl eugenol and citronellal, are the active chemicals in many essential oils, particularly basil oils. Basil oil and aforementioned monoterpenoids are potent against insect pests. However, the molecular mechanism of action of those chemical constituents is not well-understood.  It is well-known that the γ-aminobutyric acid type A receptors (GABA_AR) and nicotinic acetylcholine receptor (nAChR) are primary molecular targets of synthetic insecticides used in the market today. Furthermore, GABA_AR-targeted therapeutics have been in clinical use for many decades, including barbiturates and benzodiazepines to name a few. Here, we studied the electrophysiological effects of linalool, estragole, methyl eugenol, and citronellal on GABA_AR and nAChR to further understand their versatility as therapeutic agents in traditional remedies and as insecticides.  Our results revealed that linalool inhibits both GABA_AR and nAChR, which may explain its insecticidal activity. Linalool is a concentration-dependent, non-competitive inhibitor on the GABA_AR as the EC₅₀ values of GABA for the rat α1β3γ2L GABA_AR were not affected by linalool:  36.2 ± 7.9 µM and 36.1 ± 23.8 µM in the absence and presence of 5 mM linalool, respectively. The half maximal inhibitory concentration (IC₅₀) of linalool on the GABA_AR is approximately 3.2 mM. Considering that multiple monoterpenoids are found within the same essential oil, it is likely that linalool has a synergistic effect with methyl eugenol characterized previously as both a GABA_AR agonist and positive allosteric modulator and other monoterpenoids, thus offering a possible explanation for its sedative and anticonvulsant effects.