John D. Mattice

Measurements of year-long exposure to tree nursery workers using multiple pesticides.

A year-long nurseryworker pesticide exposure study was designed to measure and evaluate the exposure occurring to workers who had the potential for simultaneous exposure to multiple pesticides. This four-State study was conducted in five nurseries (four USDA Forest Service and one State) involved in conifer seedling production. Primary comparisons were made among nursery workers in the Pacific northwest and south central United States. Worker exposure was assessed by using patches attached to clothing, handrinse samples and urine excreted from potentially exposed workers. In addition, dislodgeable residue in rinsate from a water wash of pesticide-treated seedlings was also evaluated. Four different groups of field workers, designated as applicators, weeders, scouts and packers, were included. The pesticide absorbed dose, assessed by urine analysis of pesticide metabolites and the deposition of pesticide on patches attached to the clothing of field workers, was monitored as they performed their duties under normal conditions (e.g., typical clothing, pesticide application). Monitoring was performed for the 14 different pesticides which were used in these nurseries. Seven pesticides were studied in more detail using biological monitoring. For these compounds, metabolites known to be excreted in the urine of exposed humans or other mammals were used to estimate the dose of pesticide absorbed by the exposed workers.The highest percentage of positive samples came from dislodgeable residue samples (8.3%) followed by patch samples (3.2%), handrinse (2.9%), and urine samples (1.3%). To summarize the conclusions from the urinary excretion data, 12 of the 73 nursery workers in the study received a low absorbed dose of pesticide. Biological monitoring revealed that three pesticides (benomyl, bifenox and carbaryl) were found in the urine of some of the workers. Of the 3,134 urine samples analyzed there were 42 positive; 11 urine samples were positive for benomyl, while bifenox was responsible for 13 positives and carbaryl accounted for the remaining 18. The 12-week continuous monitoring of urine showed that metabolites of these materials were rapidly excreted; thus, no build-up in the body is anticipated. Margins of Safety (MOS) calculations were made to provide an assessment of the significance of the exposure. Based on the low frequency of positive urine samples in the study, the low levels of metabolites when they were found, their apparent rapid excretion rate and the No Observed Effect Level (NOEL) data, furnished from other sources, nursery worker exposure to pesticides in these conifer nurseries is below health threatening levels.

Evidence for allelopathic interference of Japanese honeysuckle (Lonicera japonica) to loblolly and shortleaf pine regeneration

Abstract Japanese honeysuckle presents a serious problem to the economically attractive natural regeneration of loblolly and shortleaf pine. This research investigated the potential allelopathic interference mechanisms of Japanese honeysuckle in relation to pine regeneration and growth, which may provide insight into overcoming this problem. The allelopathic potential of root exudates and leaf litter from Japanese honeysuckle was tested against loblolly and shortleaf pine seedlings. When Japanese honeysuckle and loblolly pine seedlings were grown using the same irrigation reservoir, there was no significant effect on the growth of either pine species. Exudates of Japanese honeysuckle grown as a pure culture in donor cups also produced no growth effects on pure-cultured pine seedlings grown in acceptor cups. In other assays, aqueous extracts of Japanese honeysuckle leaf tissue were toxic to duckweeds at concentrations well below levels where plasmolysis might cause effects. When Japanese honeysuckle leaf tissue was added to soil at a rate of 2 g tissue 100 g−1 soil, mean seedling height at 128 d after planting was reduced by as much as 40%. Moreover, pine seedlings grown in the presence of Japanese honeysuckle tissue exhibited significant chlorosis of the shoot and needles. Gas chromatography–mass spectroscopy analyses and high-performance liquid chromatography of Japanese honeysuckle leaf tissue aqueous extracts confirmed the presence of five compounds previously identified as possible allelochemicals: 4-hydroxycinnamic acid; 2-hydroxycinnamic acid; 3,4-dihydroxybenzoic acid; 3,4-dihydroxycinnamic acid; and chlorogenic acid. Results indicate that allelopathy plays at least a partial role in Japanese honeysuckle interference with loblolly and shortleaf pine. Nomenclature: Japanese honeysuckle, Lonicera japonica Thunb.; loblolly pine, Pinus taeda L.; shortleaf pine, Pinus echinata Mill; duckweed, Lemna minor L.

Glucosinolate and Isothiocyanate Production from Brassicaceae Cover Crops in a Plasticulture Production System

Brassicaceae cover crops are gaining attention as potential biofumigants for soil pest suppression because of their ability to release biologically active isothiocyanates (ITCs) and other compounds from hydrolysis of glucosinolates (GSLs). However, biofumigation potential of a Brassicaceae is related to its GSL and ITC profile and GSL to ITC conversion efficiency. Field and laboratory experiments were conducted to evaluate the biofumigation potential of seven Brassicaceae cover crops for weed control in plasticulture tomato and bell pepper. GSL concentration and composition varied among cover crops and between roots and shoots of each cover crop. Similar GSLs were produced in both years by roots or shoots of each cover crop, but GSL concentrations were variable between years. Total GSLs contributed to the soil by incorporation of Brassicaceae cover crop tissues were estimated between 47 to 452 nmol g−1 soil. Highest ITC concentration was detected in soil at 3 h after cover crop incorporation, and concentration decreased at later timings. GSL to ITC conversion efficiency ranged from 1 to 39%, with variation among cover crops and between years. No injury was observed in tomato and bell pepper transplanted 1 wk after cover crop incorporation, indicating the tolerance of tomato and pepper to ITCs released by the cover crops. Early-season yellow nutsedge control from Brassicaceae cover crops was ≤ 53% at 2 wk after transplanting and declined to ≤ 18% later in the season. This research demonstrates that Brassicaceae cover crops have marginal potential for early-season weed control and cannot be used as a weed control practice in commercial tomato and bell pepper production. Nomenclature: Yellow nutsedge, Cyperus esculentus L. CYPES; bell pepper, Capsicum annuum L. ‘Heritage’; tomato, Lycopersicon esculentum Mill. ‘Amelia’

Influence of Dissolved Humic Acid and Ca-Montmorillonite Clay on Pesticide Extraction Efficiency from Water Using Solid-Phase Extraction Disks

Intermittent rain can influence the sediment load in surface runofffrom agricultural fields, thereby causing variability in amounts of sediment and dissolved organic matter (DOM) in the water that could adversely affect extraction efficiency and ultimately the method sensitivity of pesticide analyses in water monitoring studies. Therefore, a study was conducted to determine the effect of purified sediment components, Ca-montmorillinite clay and commercial humic acid, on extraction efficiency of 12 pesticides from water using solid-phase extraction (SPE) disks. Batches of water at pH 6.0 and 8.0 were prepared at an ionic strength of 3 x 10 -3 M. Individual water samples (250 mL) at each pH containing 20 μg L -1 each pesticide were amended with all possible combinations of (a) commercial humic acid at either 0, 5, 10, or 25 mg L -1 dissolved organic carbon (DOC) and (b) Ca-montmorillinite amounts of either 0, 0.01, 0.1, or 1 g. Samples were prefiltered to remove clay and then extracted using solid-phase extraction (SPE) disks. Pesticides eluted from disks were analyzed by gas chromatography/mass spectroscopy (GC/MS). Pesticides within chemical families reacted similarly to treatments of pH, Ca-montmorillinite, and humic acid. The effects of Ca-montmorillinite and humic acid were generally pH-dependent and acted independently in affecting extraction efficiency. Lower recovery of most pesticides was observed at pH 8 when Ca-montmorillinite was ≥0.1 g and was attributed to greater dispersion of clay, increased surface area, and subsequent adsorption. Concentrations of DOC in humic acid had less effect on extraction efficiency when water was at pH 8 compared to water at pH 6, which was probably due to greater nonpolar interactions of pesticides to the charge-neutralized humic acid polymer.

Methane emissions from drill-seeded, delayed-flood rice production on a silt-loam soil in arkansas.

Rice ( L.) production is unique among staple food crops because the majority of the growing season typically occurs under flooded-soil conditions. Flooding the soil leads to anaerobic conditions, which are a precursor to methane (CH) production. However, no known research has investigated CH emissions from the drill-seeded, delayed-flood rice production system common in Arkansas, the leading rice-producing state in the United States. Therefore, research was conducted in 2011 to determine the effects of vegetation (rice and bare soil), chamber location (in- and between-rice rows), and nitrogen (N) fertilization (optimal and no N) on CH emissions from a silt-loam soil. Methane fluxes measured weekly from flooding until flood release were affected by vegetation, chamber location, and sample date ( < 0.05). In-row CH fluxes were <0.7 mg CH-C m h until 20 d after flooding (DAF) and <1.0 mg CH-C m h from between-row and bare soil until 41 DAF and were unaffected by fertilization over time. The largest weekly measured CH flux (31.9 mg CH-C m h) was observed from in-row rice at 41 DAF. Post-flood-release CH fluxes were affected by vegetation, fertilization, chamber placement, and sample date ( < 0.05) and accounted for approximately 3 to 7% of the season-long CH emissions. Methane emissions averaged 195 kg CH-C ha per growing season and were unaffected by fertilization. Direct measurement of CH emissions from drill-seeded, delayed-flood rice grown on a silt-loam soil will improve the accuracy of assessments of the carbon footprint and long-term sustainability of rice.

BROILER LITTER RATE EFFECTS ON NUTRIENT LEACHING FROM SOIL UNDER PASTURE VEGETATION IN THE OZARK HIGHLANDS

Litter from broiler chicken (Gallus gallus domesticus) production is a beneficial soil amendment containing organic material and many nutrients essential for proper plant growth. However, repeated land application of litter in regions of concentrated broiler production has raised concerns regarding nutrient and trace element loading in soil and potential groundwater and surface water contamination via runoff and leaching. The objective of this study was to evaluate seasonal and annual effects of broiler litter application rate on soil leachate concentrations and leaching losses of several essential plant nutrients [nitrate-N (NO3-N), ammonium-N (NH4-N), P, K, Ca, Mg, and Na] from a silt-loam soil (fine-silty, siliceous, active, mesic Typic Fragiudult) under tall fescue (Festuca arundinacea Shreb.) vegetation in the Ozark Highlands of northwest Arkansas. Equilibrium-tension lysimeters were used to continuously monitor and collect soil leachate solution from below the undisturbed root zone of small plots for a two-year period after two annual broiler litter applications at rates of 0 (control), 5.6 (low), and 11.2 (high) Mg litter ha−1. In Year 1 (May 2003-April 2004), flow-weighted mean leachate concentrations of Ca, Na, P, and Mg differed among litter rates during one or more periods; however, there were no consistent treatment effects. In Year 2 (May 2004-April 2005), leachate concentrations of Mg and NH4-N differed among litter rates during one or more periods, in which all had the greatest concentration under the low-litter treatment. There were no differences in plant nutrient leaching losses among litter rates during either full year or cumulatively over the two-year period. The land use combination of a long history of litter application, followed by several years of no litter, followed by two consecutive years of additional litter application seems to cause few water quality concerns caused by nutrient leaching, with the exception of P if leachate and/or groundwater discharge to the soil surface.

Yellow Nutsedge Interference in Polyethylene-Mulched Bell Pepper as Influenced by Turnip Soil Amendment

Abstract Methyl bromide has been widely used as a broad-spectrum fumigant for weed control in polyethylene-mulched bell pepper. However, because of environmental hazards, the phase-out of methyl bromide requires development of alternative weed management strategies. Brassicaceae plants produce glucosinolates which are hydrolyzed to toxic isothiocyanates following tissue decomposition, and therefore can be used as a cultural strategy. Field experiments were conducted in 2007 and 2009 to study the influence of soil amendment (‘Seventop’ turnip cover crop vs. fallow) and the effect of initially planted yellow nutsedge tuber density (0, 50, and 100 tubers m−2) on the interference of yellow nutsedge in raised-bed polyethylene-mulched bell pepper. Total glucosinolate production by the turnip cover crop was 12,635 and 22,845 µmol m−2 in 2007 and 2009, respectively, and was mainly contributed by shoots. In general, soil amendment with the turnip cover crop was neither effective in reducing yellow nutsedge growth and tuber production nor in improving bell pepper growth and yield compared to fallow plots at any initial tuber density. Averaged over cover crops, increasing initial tuber density from 50 to 100 tubers m−2 increased yellow nutsedge shoot density, shoot dry weight, and tuber production ≥ 1.4 times. However, increased tuber density had minimal impact on yellow nutsedge height and canopy width. Compared to weed-free plots, interference of yellow nutsedge reduced bell pepper dry weight and marketable yield ≥ 42 and ≥ 47%, respectively. However, bell pepper dry weight and yield reduction from 50 and 100 tubers m−2 were not different. Light was the major resource for which yellow nutsedge competed with bell pepper. Yellow nutsedge shoots grown from initially planted 50 and 100 tubers m−2 caused up to 48 and 67% light interception in bell pepper, respectively. It is concluded that yellow nutsedge interference from initial densities of 50 and 100 tubers m−2 are equally effective in reducing bell pepper yield and that soil biofumigation with turnip is not a viable management option for yellow nutsedge at these densities. Nomenclature: Yellow nutsedge, Cyperus esculentus L. CYPES; bell pepper, Capsicum annuum L. ‘Heritage’; turnip, Brassica rapa L. ‘Seventop’.

Gas chromatographic determination of picloram in human urine

Picloram (4-amino-3,5,6-trichloropicolinic acid) is used to control broadleaf weeds and woody plants. It is used in forestry for site preparation and to help release pine seedlings from broadleaf competition. The use of any pesticide requires that we monitor not only its effectiveness but also the exposure of human beings to the compound. Methods for analyses of exposure and the fate of compounds differ for individual pesticides. Although methods have been developed for analysis of picloram from urine, none have been reported using boron trifluoride methylation with C18 cartridge cleanup and electron capture detection. Nolan et al. (1984) have reported that 88-94% of picloram that had been orally ingested by human volunteers was excreted unchanged in the urine within 72 hours. In the same paper they report an analytical method for picloram in urine using GC/MS with a limit of quantification of 10 ppb. Tonder and Daugherty (1981) have reported an analytical screening method for acidic toxic substances involving diazo-methane derivatization followed by florisil cleanup. The percent recovery for picloram was 60-63% at 40 ppb. Draper (1982) also used diazomethane derivatization with a recovery of 104 ~ 6% for 4 replications fortified at 100 ppb. Libich et al. (1984) analyzed for picloram with a Hall detector in the chlorine mode following base hydrolysis and methylation with boron trifluoride in methanol. The mean recovery was 80% with a range of 76% to 90%. In order to complete one of our research projects, we needed an analytical method for picloram in urine using election capture detection. We also wished to avoid the use of diazomethane due to the potential health hazards associated with it. Our method affords a limit of quantification of 10 ppb.

ANALYSIS OF THE ALLELOPATHIC POTENTIAL OF RICE USING K-MEANS CLUSTERING OF HPLC CHROMATOGRAMS

Allelopathy is the ability of an organism to affect the growth of another organism through the introduction of chemical compounds into the environment. Several researchers have reported rice inhibition of the growth of weed species such as barnyard grass and ducksalad. The objective of this study was to relate patterns found in HPLC chromatograms for leaf extracts of different rice accessions to their weed control activity. K-means cluster analysis was performed on 20 peak heights from chromatograms from 40 rice accessions. The resulting clusters corresponded to observed behavior of the accessions reported in other sources. Stepwise discriminant analysis was used to determine if the number of peaks needed to separate accession types could be reduced.