In vitro metabolism of EPN and EPNO in susceptible and resistant strains of house flies

EPN is twice as toxic as EPNO to house flies from both the Diazinon-resistant strain and the susceptible strain. EPN and EPNO are also eight times more toxic to the susceptible than the resistant strain. This is due to the ability of the resistant strain to metabolize these compounds to a greater extent. Metabolism by the glutathione S-transferases present in the 100,000g supernatant is more extensive than that by the NADPH-dependent microsomal mixed-function oxidases. The glutathione S-transferases are the major route of metabolism for EPN and appear to be the principal mechanism conferring resistance. EPN was metabolized by the microsomal fraction via oxidative desulfuration to the oxygen analog, EPNO, and by oxidative dearylation to p-nitrophenol. EPNO was metabolized by the same system to p-nitrophenol and desethyl EPNO as well as to an unknown metabolite. The soluble fraction metabolized EPN to p-nitrophenol, S-(p-nitrophenyl)glutathione, O-ethyl phenylphosphonothioic acid, and S-(O-ethyl phenylphosphonothionyl)glutathione. The identification of the latter conjugate demonstrates a new type of metabolite of organophosphorus compounds. EPNO was metabolized by the soluble fraction to p-nitrophenol and S-(p-nitrophenyl)glutathione.     

Spectral interactions of insecticide synergists with microsomal cytochrome P-450 from insecticide-resistant and susceptible house flies

The spectral interactions of 45 insecticide synergists and related compounds with oxidized and reduced cytochrome P-450 from microsomes of insecticide-resistant and -susceptible house flies were investigated. The type III interaction typical of piperonyl butoxide was the most common spectral interaction for the compounds studied. In addition to this, several other varients of the type III interaction were noted. In general these responses with house fly microsomes were similar to those reported for mammals, although some minor species and strain differences were observed. The cytochrome P-450 from susceptible house flies, although reported previously not to exhibit type I difference spectra with many xenobiotics, was found to elicit this spectral response with several methylenedioxyphenyl compounds.     

Metal Mine Tailings and Sludge CO-Deposition in a Tailings Pond

In the Lower Cell of the Heath Steele mine tailings arealocated 50 km north of the city of Miramichi, New Brunswick,Canada, tailings and lime treatment sludge were co-depositedand the effluent occasionally exceeded regulatory dischargelimits for total suspended solids (TSS), especially on verywindy days. A combined field and laboratory investigationwas undertaken during 1998-1999 to identify the cause of thehigh TSS. The methodology included field measurement of windvelocity and sampling of bed tailings, sludge,suspended sediment, and the water cover. The samples werethen subjected to various laboratory examinations using x-raydiffraction, scanning electron microscopy interfacedwith energy dispersion x-ray spectroscopy, critical shearstress measurements, and water chemistry analysis. Thesuspended sediment was found to be composed primarily ofcalcite and metal hydroxides derived from the bed sludge inthe cell. Only a very small amount of tailings (less than5%) was detected in the suspended sediment. The sludge,which covered the tailings in the shallow western section ofthe Lower Cell at depths less than 1 m, was a loose, low-densitymaterial with a low critical shear stress (approximately 0.058 Pa). In shallow water cover (less than 1 m), calculated bed shearstress mobilized by wind-induced waves and return currents exceeded the critical shear on a number of occasions, resultingin resuspension of the sludge and hence high TSS. Although occasional elevated zinc concentrations appeared to follow a similar pattern to high TSS, there was no evidence that thesuspended sludge sediments would release metals into the watercover, due to the high pH of the Lower Cell water cover. Since the tailings did not resuspend significantly, it was clear thatat water cover depth less than 1 m, sludge was eroded instead oftailings, and thus provided a barrier against tailings resuspension. As part of the final closure scheme for the HeathSteele tailings area, sludge and tailings were dredged and relocated from areas where the water cover was < 1 m to deeperwater cover areas to ensure that the effluent met required totalsuspended solids discharge criteria.     

Effects of Kocide 101® on the bean (Phaseolus vulgaris L.)‐Rhizobium symbiosis

A glasshouse study was undertaken to investigate the effects of the copper fungicide Kocide 101 and its residues in soil on the growth, nodulation and nitrogen fixation of beans (Phaseolus vulgaris L.). The soil used was a sandy clay loam classified as Typic Rhodustalf. The bean variety SUA 90 was used as test crop. The bean rhizobia strains CIAT 899, PV, and a local isolate were used. Kocide 101 applied at the recommended rate (equivalent to 1.7 mg kg^‐1 soil) had no significant negative effects on the growth, nodulation or nitrogen fixation of bean plants. Higher levels of Kocide 101 significantly (P < 0.05) reduced plant growth, nodulation and nitrogen fixation. The bean plants inoculated with the “local isolate”; rhizobia had the highest dry matter weights, nodule numbers and nodule dry weights, and also had more N fixation. They were followed by those inoculated with the PV, strain and, lastly, those inoculated with CIAT 899. The growth and nodulation of bean plants were still curtailed by the Kocide 101 residues four months after the fungicide was first applied to the soil. Therefore, occurrence of high levels of Kocide 101 in soils can have long‐term effects on the performance of the bean‐rhizobia symbiosis.     

Adaptation of the LIGNUM model for simulations of growth and light response in Jack pine

LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, that combines tree metabolism with a realistic spatial distribution of morphological parts. We hypothesize that its general concepts, which include the pipe model, functional balance, yearly carbon budget, and a set of architectural growth rules, are applicable to all trees. Adaptation of the model to Pinus banksiana, a widespread species of economic importance in North America, is demonstrated.

Conversion of the model to Jack pine entailed finding new values for 16 physiological and morphological parameters, and three growth functions. Calibration of the LIGNUM Jack pine model for open grown trees up to 15 years of age was achieved by matching crown appearance and structural parameters (height, foliage biomass, aboveground biomass) with those of real trees. A sensitivity study indicated that uncertainty in the photosynthesis and respiration parameters will primarily cause changes to the net annual carbon gain, which can be corrected through calibration of the growth rate. The effect of a decrease in light level on height, biomass, total tree branch length, and productivity were simulated and compared with field data. Additional studies yielded insight into branch pruning, carbon allocation patterns, crown structure, and carbon stress. We discuss the value of the LIGNUM model as a tool for understanding tree growth and survival dynamics in natural and managed forests.     

Comparing the Impact of a Neonicotinoid and Biorational Agroneem on Herbivorous and Beneficial Arthropods on Cowpea and Tomato

Cowpea （Vigna unguiculata L. Walp.） and tomato （Lycopersicum esculentum L. Karst） are attacked by a wide range of insect pests worldwide. In many cases, pesticides are used to control the pests. In 2010 and 2011, we conducted field experiments to evaluate and compare the effectiveness of a biorational （Agroneem~） and conventional pesticide （imidacloprid or thiamethoxam） on insect pests of these crops. In the first year, two varieties of cowpea （Mississippi Silver and Pinkeye Purple Hull） and two of tomato （Mariana and German Johnson） were used; in the second year, the better performing of each group （Mississippi Silver and Mariana） were used for the study. A split-plot design with four replications in Year 1, and a randomized complete block design with six treatment combinations in Year 2. In the first year, both pesticide groups were applied following manufacturer＇s recommendation （10-14 d cycles）; and in the second year, the application of the pesticides was driven by economic thresholds level （ETL） of insect pests. The most prevalent species of insects recorded in both crops were in the families： Chrysomelidae, Pentatomidae, Cicadellidae, Vespidae, Sarcophagidae, Thripidae and Sphingidae. In both years, the diversity of insects on cowpea was greater than on tomato and more insects were observed in the second year compared to the first, despite the absence of significant difference （P 〉 0.05） between varieties in the treated plots. The yield of cowpea and tomato was comparable in all sprayed plots.