Fungicides Penconazole Research Articles

A long term field study of the effect of fungicides penconazole and sulfur on yeasts in the vineyard

This research deals with how two fungicide treatments against powdery mildew, penconazole as a systematic fungicide and sulfur as an inorganic broad-spectrum fungicide, affect the diversity and density of wine yeasts associated with grape berry surfaces and subsequent spontaneous fermentations. Unlike other studies in this area, this work aims to evaluate this effect on the population dynamics in the environment, the conditions of which are not reproducible in the laboratory. A long term (three year) sampling plan was thus devised. A minimum inhibitory concentration assay was also carried out in the laboratory in order to prove the influence of these antifungals on yeast populations. While both antifungal treatments (penconazole and sulfur) were similarly effective against powdery mildew, each had a very different effect on yeast populations. Penconazole showed the most negative effect on biodiversity in the vineyard and was the fungicide to which the isolated yeasts showed the greatest sensitivity. This study therefore evidences the suitability of treatment with sulfur, in both conventional and organic viticulture, to preserve the yeast population associated with grape berries, in particular the Saccharomyces cerevisiae species.

Comparative Assessment of Phosphite Formulations for Apple Scab (Venturia inaequalis) Control

Potassium phosphite is a widely used plant protection agent. However, a suite of phosphite formulations with alternative cation attachments (calcium, copper, silicon, zinc) are commercially available. The plant protective properties of these formulations have received little attention. This study evaluated five phosphite formulations for plant protection purposes against the foliar pathogen apple scab (Venturia inaequalis) under field conditions. In addition, a comparative analysis against the synthetic fungicide penconazole, which is widely used for apple scab control, was conducted. Greatest reductions in leaf and fruit scab severity were achieved by sprays of the synthetic fungicide penconazole. However, all phosphite formulations evaluated significantly reduced leaf and fruit scab severity at the cessation of the growing season. Within the phosphites tested, the greatest reductions in leaf and fruit scab severity were achieved in the order: copper phosphite > silicon phosphite > zinc phosphite > calcium phosphite > potassium phosphite > control. The advantages and disadvantages of these phosphite formulations for scab control are discussed.

Water-retaining Polymer and Fungicide Combinations Reduce Disease Severity Caused by Horsechestnut Leaf Blotch [Guignardia aesculi (Peck) VB Stewart

The influence of six commercially available fungicides incorporated into a water-retaining polymer and applied to the root system of horsechestnut (Aesculus hippocastanum L.) as a dip at the time of planting was conducted. Potential increases in resistance against the foliar pathogen Guignardia leaf blotch (Guignardia aesculi) was then monitored over two growing seasons. Trials were conducted in 2007 and duplicated in 2008. A comparative evaluation of the fungicide penconazole commercially used for Guignardia leaf blotch control was studied by spraying trees at the manufacturer’s recommended rate of four times during the first growing season but none in the second. None of the treated or control trees died as a result of Guignardia leaf blotch attack during the course of the study and none of the fungicide and water-retaining polymer combinations evaluated was phytotoxic to the test trees. Efficacy as Guignardia leaf blotch protectant compounds over the first growing season was demonstrated when fungicides were incorporated into a water-retaining polymer. Reductions in Guignardia leaf blotch severity were mirrored by increases in leaf chlorophyll fluorescence as a measure of leaf photosynthetic activity and leaf chlorophyll content SPAD values. There were little differences in the magnitude of control efficacy between the fungicides evaluated. Limited efficacy of any of the fungicide and water-retaining polymer combinations as Guignardia leaf blotch protectant compounds was, however, demonstrated the following year after application indicating a fungicide and water-retaining polymer root dip provided one growing season protection only. Application of a water-retaining polymer alone had no effect on reducing Guignardia leaf blotch severity. Based on visual Guignardia leaf blotch severity ratings, greatest protection in both the 2007 and 2008 trial was provided by the synthetic fungicide penconazole applied as a foliar spray four times during the growing season. No efficacy of penconazole foliar sprays as leaf blotch protectant compounds was demonstrated the following year, indicating annual sprays against Guignardia leaf blotch are required for control.

Cancer-related genes transcriptionally induced by the fungicide penconazole

Penconazole is a systemic triazole fungicide mainly used on grapes. The UE Maximum Residue Level (MRL) for penconazole is set at 0.2ppm in wine and grapes. In the aim of identifying potential biomarkers of exposure to penconazole and possibly highlighting its endocrine disrupting mode of action, we used a transcriptomics-based approach to detect genes, that are transcriptionally modulated by penconazole, by using an appropriate in vitro model. T-47D cells were treated with commercial penconazole or penconazole contaminated grape extracts for 4h at doses close to the MRL. The whole-genome transcriptomic profile was assessed by using genome 44K oligo-microarray slides. The list of common genes generated by the two treatments could be representative of potential markers of exposure. In order to understand the role of these genes in key events related to adversity, a pathway analysis was performed on a list of genes with the same modulation trend (up or down). The analysis returned a set of genes involved in Thyroid Cancer Pathway, thus confirming a role of penconazole in endocrine disrupting mediated effects and strongly suggesting a possible mode of action in thyroid carcinogenesis.

Use of Cultural Filtrates of Certain Microbial Isolates for Powdery Mildew Control in Squash

Use of Cultural Filtrates of Certain Microbial Isolates for Powdery Mildew Control in SquashPowdery mildew induces significant losses in yield and quality of squash. Therefore, culture filtrates of certain microbial isolates, (Epicoccum nigrum,Epicoccum minitans,Epicoccumsp.,Trichoderma harzianum,Trichoderma virideandBacillus pumilus) were used alone, and in combination with the fungicide penconazole to control powdery mildew in squash, under field conditions. Moreover, GC-MS analysis was carried out to identify the chemical components of the most effective culture filtrates against powdery mildew pathogen. The results showed that culture filtrates of different microbial isolates (except forTrichoderma harzianum) were more effective against powdery mildew in squash than the tested fungicide alone at the recommended levels, in both tested seasons. The results also showed that mixing different culture filtrates with penconazole improved efficiency against powdery mildew compared to using the fungicide alone, in both tested seasons. The efficacy of the culture filtrates of the tested microbial isolates against powdery mildew were due to the presence of a mixture of known antifungal compounds. The results suggest the possible use of the culture filtrates of the tested microbial isolates as alternative to fungicides, in powdery mildew control. Also, this study suggests the possible mixing of the culture filtrate of the tested biocontrol agents with fungicides to minimize the applied amount of fungicides.

Development of Immunoassays for the Detection of the Fungicide Penconazole and Its Urinary Metabolite

Monoclonal antibodies were raised to haptens containing moieties common to both the triazole fungicide penconazole and its proposed primary urinary metabolite (4-(2,4-dichlorophenyl)-5-(H-1,2,4-triazol-1-yl)pentoic acid). The monoclonal antibody 2E4 was used to develop competitive ELISA assays where binding of antibody to immobilized haptens conjugated to BSA competed with penconazole or its metabolite in solution. At pH 4.0 and pH 8.0, penconazole was detected with an IC50 of 1.0-1.2 microg/L respectively and at pH 4 penconazole metabolite was detected with an IC50 of 0.9 microg/L. These assays were specific for penconazole and/or its metabolite compared to other triazole fungicides. The immunoassay conditions optimal for penconazole metabolite (pH 4.0) were used and applied to the analysis of spiked human urine, and following sample extraction using a C18 SPE column, could detect 0.5 microg/L metabolite. This is the first report of an immunoassay to the urinary metabolite of penconazole, an assay with application in the monitoring of occupational and non-occupational exposure to this commonly used pesticide.

Effect of Spent Mushroom Substrate Amendment of Vineyard Soils on the Behavior of Fungicides: 2. Mobility of Penconazole and Metalaxyl in Undisturbed Soil Cores

Mobility of fungicides penconazole and metalaxyl in unamended and amended vineyard soils with fresh and composted spent mushroom substrates (F-SMS and C-SMS) was studied. Experiments were performed in non-incubated and incubated (outdoors for 77 days) undisturbed soil cores under non-saturated flow conditions. Breakthrough curves (BTC) of metalaxyl leaching were delayed with regard to the tracer ion, and they showed an incomplete leaching in all soil cores after the addition of 2.5-4.5 pore volumes. A decrease of the maximum peak concentration in C-SMS soils with regard to unamended soils (up to 24-fold in Viana soil) and an increase in the fungicide retention by soils (up to 8-fold in the first segment of Viana soil core) was observed. However, a decrease (up to 2.6-fold in Sajazarra soil) or an increase (up to 1.4-fold in Aldeanueva soil) of the maximum peak concentration in F-SMS soils was observed. No leaching of penconazole was observed in all cases. After fungicide incubation in soil cores, the amounts of metalaxyl retained and leached decreased significantly by 1.24-37.8-fold and 1.17-302-fold, respectively, whereas no changes were observed for penconazole. Degradation of metalaxyl occurred in non-incubated soil and increased after incubation (two metalaxyl metabolites were detected in the leachates and the soil extracts), but it was not seen for penconazole in any case. In consequence, the addition of SMS as amendment to soil (especially C-SMS) enhanced adsorption of both fungicides, although metalaxyl could be available for degradation. This effect contributes to prevent groundwater contamination by metalaxyl, but it could contribute to increase the surface water contamination by penconazole, because adsorption protects this fungicide from degradation, increasing its persistence in soils.

Effect of Spent Mushroom Substrate Amendment of Vineyard Soils on the Behavior of Fungicides: 1. Adsorption−Desorption of Penconazole and Metalaxyl by Soils and Subsoils

The effect of the addition of fresh and composted spent mushroom substrates (F-SMS and C-SMS) to vineyard soils on the adsorption-desorption of penconazole and metalaxyl was studied under laboratory conditions. SMS is a promising agricultural residue as an amendment to increase the soil organic matter (OM) content. It may also modify the behavior of fungicides applied to vineyards. Freundlich Kf adsorption constants of both fungicides by soils and subsoils from three experimental plots unamended and amended in the field ranged between 2.78 and 13.4 (penconazole) and 0.14 and 0.67 (metalaxyl) with scant differences for unamended soil and subsoil. However, Kf values of amended soils were higher than those corresponding to subsoils and generally higher than those of unamended soils (up to 2.3 times for penconazole and 1.3 times for metalaxyl). The influence of SMS treatment (fresh or composted) was observed in the adsorption of the most hydrophobic fungicide penconazole. Simple and multiple correlations between soil and subsoil properties and adsorption constants indicated the influence of the OM on the adsorption of both fungicides, together with the clay, silt, and CaCO(3) content for metalaxyl and the pH for penconazole. The results revealed changes in the adsorption-desorption processes of these fungicides, which could give rise to a decrease in the mobility of metalaxyl (highly water-soluble) and an increase in the retention of penconazole (more hydrophobic). These effects could have an impact on surface and/or groundwater contamination.

The Influence of Calcium Sprays to Reduce Fungicide Inputs Against Apple Scab [Venturia inaequalis (Cooke) G. Wint.

A goal of pathogen management in the arboriculture industry should be to eliminate or reduce the amount of active ingredients of synthetic fungicides used within a growing season. The aim of this research paper was to evaluate a nonfungicidal pathogen management system by investigating the hypothesis that replacing an apple scab fungicide spray program with calcium reduces fruit and leaf scab severity. In addition, a separate study investigated if a relationship existed between calcium concentrations within foliar tissue of resistant, intermediate, and sensitive apple species and varieties toward scab infection. A number of commercially available calcium products were applied to apple cv. Crown Gold trees at four distinct growth stages (bud break, 90% petal fall, early fruitlet, two weeks after early fruitlet). A comparative evaluation of the synthetic fungicide penconazole commercially used for scab control was also conducted. The experiment was performed in 2006 and repeated in 2007 at the University of Reading Experimental Field Site (UK). Application of calcium sprays significantly reduced the leaf and fruit scab severity of apple cv. Crown Gold however; in a separate study no relationship existed between foliar calcium content and susceptibility to apple scab attack between resistant, intermediate, and sensitive Malus species. Greatest protection in both field trials was provided by the synthetic fungicide penconazole. Within the calcium products evaluated, greatest protection in both field trials was provided by calcium chloride and calcium hydroxide. The integration of calcium foliar sprays into existing scab management practices offers a useful addition to reduce scab severity on ornamental apples that has applicability against other foliar diseases frequently encountered within urban landscapes.

Field evaluation of systemic inducing resistance chemicals at different growth stages for the control of apple ( Venturia inaequalis) and pear ( Venturia pirina) scab

Two field trials were conducted using established apple ( Malus cv. Golden Delicious) and pear ( Pyrus communis ‘Williams’ Bon Chrétien') to assess the efficacy of three commercially available systemic inducing resistance (SIR) products, Messenger (a.i. Harpin protein), Phoenix (a.i. Potassium phosphite) and Rigel (a.i. Salicylic acid derivative) applied at four different growth stages of tree development (bud break, green cluster, 90% petal fall, early fruitlet) against the foliar pathogens Venturia inaequalis and Venturia pirina which cause apple and pear scab respectively. A conventional synthetic fungicide (penconazole) used within the UK for apple and pear scab control was included for comparison. Little efficacy as scab protectants was demonstrated when each SIR product and penconazole was applied at only two growth stages (bud break, green cluster). However when the above compounds were applied at three or more growth stages efficacy as scab protectants was confirmed. The synthetic fungicide penconazole provided greatest protection against apple and pear scab in both the 2006 and 2007 field trials. There was little difference in the magnitude of scab protection conferred by each SIR agent. Results suggest application of at least three sprays during bud break to early fruitlet formation with an appropriate SIR agent may provide a useful addition to existing methods of apple and pear scab management under field conditions.

Evaluation of film forming polymers to control apple scab ( Venturia inaequalis (Cooke) G. Wint.) under laboratory and field conditions

A detached leaf bioassay was used to determine the influence of several film forming polymers and a conventional triazole fungicide on apple scab ( Venturia inaequalis (Cooke) G. Wint.) development under laboratory in vitro conditions, supported by two field trials using established apple cv. Golden Delicious to further assess the efficacy of foliar applied film forming polymers as scab protectant compounds. All film forming polymers used in this investigation (Bond, Designer, Nu-Film P, Spray Gard, Moisturin, Companion PCT12) inhibited germination of conidia, subsequent formation of appressoria and reduced leaf scab severity using a detached leaf bioassay. Regardless of treatment, there were no obvious trends in the percentage of conidia with one to four appressoria 5 days after inoculation. The synthetic fungicide penconazole resulted in the greatest levels of germination inhibition, appressorium development and least leaf scab severity. Under field conditions, scab severity on leaves and fruit of apple cv. Golden Delicious treated with a film forming polymer (Bond, Spray Gard, Moisturin) was less than on untreated controls. However, greatest protection in both field trials was provided by the synthetic fungicide penconazole. Higher chlorophyll fluorescence Fv/Fm emissions in polymer and penconazole treated trees indicated less damage to the leaf photosynthetic system as a result of fungal invasion. In addition, higher SPAD values as measures of leaf chlorophyll content were recorded in polymer and penconazole treated trees. Application of a film forming polymer or penconazole resulted in a higher apple yield per tree at harvest in both the 2005 and 2006 field trials compared to untreated controls. Results suggest application of an appropriate film forming polymer may provide a useful addition to existing methods of apple scab management.

The Influence of Systemic Inducing Resistance Chemicals for the Control of Oak Powdery Mildew (Microsphaera alphitoides) Applied as a Therapeutic Treatment

A 2 year field trial was conducted using established English oak (Quercus robur L.) to assess the efficacy of four commercially available systemic-inducing resistance (SIR) compounds (salicylic acid, potassium phosphite, harpin protein, betaine) applied as a single therapeutic spray treatment against the foliar pathogen oak powdery mildew (Microsphaera alphitoides). In addition, a comparative evaluation of a conventional spray program (3 week spray intervals) used within the United Kingdom for powdery mildew control was conducted using the fungicide penconazole. The SIR-inducing compound containing betaine and a single spray treatment of penconazole had no significant influence on disease severity and specific activity of peroxidase and superoxide dismutase in both the 2005 and 2006 trials. Salicylic acid and potassium phosphite had no significant long-term effect on disease severity, although a short-term reduction in disease severity was recorded that was associated with enhanced leaf peroxidase and superoxide dismutase activity. A single therapeutic application of the SIR-inducing agent harpin protein significantly reduced disease severity of powdery mildew in the 2005 trial. No significant effects, however, were recorded in the 2006 trial. Only repeat spray applications of penconazole significantly reduced disease severity of oak powdery mildew in the 2005 and 2006 trials. The fungicide penconazole appears also to posses marginal SIR properties.

Rapid Estimation of Octanol–Water Partition Coefficient for Triazole Fungicides by MEKC with Sodium Deoxycholate as Surfactant

A rapid estimation of octanol–water partition coefficient (log Pow) was developed for triazole fungicides by micellar electrokinetic chromatography (MEKC). Five standard compounds with known log Pow values from 2.9 to 4.3 (cyproconazole, bromuconazole, epoxiconazole, bitertanol and difenoconazole) were used for constructing the calibration curve of the log Pow against the MEKC retention factor, log k. A linear relationship was achieved between log Pow and log k, in the MEKC system containing 40 mM sodium deoxycholate (SDC) and 4 mM borate buffer at pH 9.3, with a correlation of determination, r2 = 0.9905. The log Pow values of four test compounds of triazole fungicides (triadimenol, myclobutanil, propiconazole and penconazole) were calculated based on the log k values measured by MEKC and the slope and intercept of the calibration curve. This MEKC method can give good estimation of the log Pow of the four test compounds of triazole fungicides with the differences between the literature log Pow values and estimated log Pow from the MEKC method were from 0.15 to 0.23 log units.

The Use of Film-Forming Polymers to Control Guignardia Leaf Blotch and Powdery Mildew on Aesculus hippocastanum L. and Quercus robur L.

The effects of four commercially available film-forming polymers (Bond, Designer, Spray Gard, Nu-Film-P) on disease severity of powdery mildew (Microsphaera alphitoides Griffon and Maubl.) on English oak (Quercus robur L.) and Guignardia leaf blotch (Guignardia aesculi (Peck) Stewart) on horsechestnut (Aesculus hippocastanum L.) were examined in a field experiment. In addition, a comparative evaluation of the fungicide penconazole, commercially used for powdery mildew control, was conducted. Effects on tree vitality were also assessed by measuring leaf chlorophyll fluorescence and chlorophyll concentrations. Irrespective of tree species, Nu-Film-P and Spray Gard did not significantly influence disease severity of powdery mildew and Guignardia leaf blotch. Likewise, no significant effects of these two film-forming polymers on chlorophyll fluorescence and chlorophyll content were recorded. Reduction in disease severity following spray applications of the film-forming polymers Bond and Designer was statistically comparable with penconazole. None of the film-forming polymers and fungicide evaluated was phytotoxic to the test trees. Results suggest that application of an appropriate film-forming polymer may provide a useful addition to existing methods of plant disease control.

Effect of the modification of natural clay minerals with hexadecylpyridinium cation on the adsorption–desorption of fungicides

Clay minerals, montmorillonite (M), illite (I), kaolinite (K), muscovite (Mu), sepiolite (S) and atapulgite (A), modified with the organic cation hexadecylpyridinium (HDPY) were studied as sorbents of two fungicides of different hydrophobicity, penconazole and metalaxyl, using adsorption–desorption isotherms. The Freundlich constant values were low for the adsorption of the fungicides by natural clays and increased when the minerals were saturated with the organic cation. In HDPY-M, the K f constant increased 190-fold for the adsorption of penconazole and 67-fold for the adsorption of metalaxyl. Adsorption of the fungicides by the organo-clays at an initial concentration of 25 µg/mL was related to their organic matter content, the highest adsorption values being found in HDPY-M, HDPY-I and HDPY-A, and the increase in adsorption was greatest for the more hydrophobic fungicide penconazole. Desorption of fungicides from modified clays pointed to a high degree of stability for penconazole adsorbed by HDPY-M. In the remaining samples, the stability of this pesticide was low and the stability of metalaxyl adsorbed by all the organo-clays was also low. The results obtained point to the potential value of clay minerals modified with HDPY for immobilising pesticides with different degrees of hydrophobicity. Of special interest is the HDPY-M sample, which could be considered for use in clay barriers aimed at protection of soil and water pollution by hydrophobic pesticides.

SOIL PROPERTIES INFLUENCING THE ADSORPTION AND MOBILITY OF PENCONAZOLE IN VINEYARD SOILS

A study was made of the adsorption and mobility of the fungicide penconazole (1-[2-(2,4-dichlorophenyl)pentyl]-1H-1,2,4-triazole) in 19 vineyard soils with low organic matter contents (0.31-1.98%) and in seven uncropped soils from oak and beech forests or grasslands with higher organic matter contents (3.30-8.24%). Adsorption isotherms were obtained using the batch equilibrium technique, and mobility was studied using soil thin layer chromatography. The aim of this study was to evaluate the adsorption and mobility behavior of this relatively new fungicide in vineyard soils. The adsorption isotherms fit the Freundlich adsorption equation, the Kf values ranged between 10.3 and 151, and the nf values were always lower than unity. The Kf constants were correlated positively with the soil organic matter content. According to the r2 determination coefficients, the organic matter content accounted for 85% of the variance in adsorption when all soils were considered together and for 76% and 36%, respectively, when considering the natural and vineyard soils. In no case was any influence of clay or silt contents on adsorption observed. According to the Rf values obtained, penconazole is immobile in 8% of soils and slightly mobile in 92% of soils. Adsorption of the fungicide by individual soil components, clay minerals and humic acid, confirms the importance of the organic matter fraction as the only soil parameter that affects adsorption. The results obtained indicate that vertical leaching of penconazole is low. The fungicide may, however, cause surface pollution of the soil because of its accumulation. If its degradation rate is low, this accumulation may lead to the pollution of surface water through runoff of the sorbed pesticide.

Efficacy of trifloxystrobin (Flint), a new strobilurin fungicide, in controlling powdery mildews on apple, mango and nectarine, and rust on prune trees

Trifloxystrobin is a new strobilurin fungicide, active against a wide range of fungal plant pathogens. The present study shows that trifloxystrobin is highly effective in controlling powdery mildews on field-grown apple, mango and nectarine trees and rust disease on prune trees. In the majority of the field experiments conducted during 1998–1999, trifloxystrobin (at a concentration of 0.01–0.015% v/v) was superior to demethylation inhibitors (DMI fungicides) or sulphur. Trifloxystrobin was significantly ( p<0.05) more effective than the DMI fungicide penconazole in controlling primary and secondary infections of powdery mildew on apple trees, and it provided 95–100% protection compared with non-treated trees. Similarly, trifloxystrobin was more effective than either myclobutanil or penconazole in controlling powdery mildew on fruit and leaves of nectarine trees. Trifloxystrobin provided the best control of powdery mildew on bloom clusters of mango, while sulphur, hexaconazole, and kresoxim-methyl were less effective. Trifloxystrobin effectively inhibited rust on prune trees and provided 98.0% protection, compared with the control. Trifloxystrobin is an excellent compound for efficient integration into control programs against fungal pathogens in apple, mango and stone fruit orchards.

AnUstilago maydisMutant Partially Blocked in P45014DMActivity Is Hypersensitive to Azole Fungicides

AnUstilago maydisergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14α-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14α-methyl sterols, eburicol, 14α-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.

Interactive effects between EBI fungicides (prochloraz, propiconazole and penconazole) and OP insecticides (dimethoate, chlorpyrifos, diazinon and malathion) in the hybrid red-legged partridge

The toxicokinetic interactions between the ergosterol-biosynthesis-inhibiting (EBI) fungicides prochloraz, propicon-azole, and penconazole and the organophosphorus (OP) insecticides dimethoate, chlorpyrifos, and diazinon have been studied in the hybrid red-legged partridge. The inhibition of serum butyrylcholinesterase (BuChE) activity provided a useful biochemical indicator of the generation of the toxic oxon metabolites of these OP insecticides. Birds pretreated with 180 mg/kg prochloraz tended to show a greater inhibition of serum BuChE activity at 1, 4, and 24 h following oral exposure to either of the OPs dimethoate (3 mg/kg) or chlorpyrifos (9 mg/kg) compared to birds pretreated with corn oil. Prochloraz-pretreated birds also showed a tendency toward an increased inhibition at 24 h following dosing with the OP diazinon (4.3 mg/kg) compared to corn oil controls. In the case of dimethoate, the inhibition of serum BuChE activity was significantly greater in treated birds than controls at 24 h. Birds pretreated with the EBI fungicide propiconazole (200 mg/kg) showed a similar inhibition of serum BuChE activity to those pretreated with corn oil following administration of 167 mg/kg malathion. Pretreatment with the EBI fungicide penconazole (200 mg/kg) produced significantly greater depression of serum BuChE activity at 1, 4, and 24 h after dosing with malathion, when compared to corn oil controls. The tendency toward increased inhibition of serum BuChE activity by each of the OPs in prochloraz-pretreated birds was attributed to an increased activation of the compound to its active oxon form as a consequence of induction of microsomal monooxygenases by prochloraz.

Fungicides and photochemistry: Photodegradation of the azole fungicide penconazole

In order to examine the photostability of the fungicide penconazole (1-(2,4-dichloro-beta-propylphenethyl)-1H-1,2,4-triazole, 1) in the field, model experiments with organic solvents were performed. Photodegradation (lambda > 280 nm) of penconazole was found to be more efficient in isopropanol and cyclohexane solution than in the presence of cyclohexene. Photolysis in isopropanol and cyclohexane resulted in considerable formation of 1-(4-chloro-beta-propylphenethyl)-1H-1,2,4-triazole (2) and 5H,6H-(1,2,4-triazolo)-[5,1-a]-9-chloro-6-propyl-isoquinoline (3). Furthermore, photodehalogenation of 3 yielded traces of 5H,6H-(1,2,4-triazolo)-[5,1-a]-6-propyl-isoquinoline (4) and, in the presence of isopropanol 5H,6H-(1,2,4-triazolo)-[5,1-a]-9-(2-hydroxy-2-methylethyl)-6-propyl- isoquioline (5). Additionally, a lot of polar products were found in high yields which could not be isolated and characterized individually. In the presence of cyclohexene, on the other hand, photodecomposition and photodehalogenation to photoproduct 2 were found to be the main degradation pathways and photoproduct 3 was only detected as a trace component.