Soil Fungicide Research Articles

Simultaneous determination of three strobilurin fungicide residues in fruits, vegetables and soil by a modified quick, easy, cheap, effective, rugged (QuEChERS) method coupled with gas chromatography-tandem mass spectrometry

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method followed by a modified quick, easy, cheap, effective, rugged (QuEChERS) method for the analysis of three strobilurin fungicide residues (picoxystrobin, kresoxim-methyl and trifloxystrobin) in fruits, vegetables and soil was developed and validated. The three fungicides were extracted with ethyl acetate and cyclohexane (v/v = 1/1), and subsequently cleaned up using a combination of primary secondary amine and graphitized carbon black prior to GC-MS/MS analysis. The three fungicides were qualitatively determined using the multiple reaction monitoring mode with two ion transitions measured for each fungicide and evaluation by collision tests, and were determined quantitatively using the external standard method. Recovery studies were performed at three fortification levels of 0.005, 0.05, and 0.5 mg kg−1 in blank cucumber, tomato, apple, grape and soil samples. The overall average recoveries ranged from 87% to 112%, with intra-day relative standard deviations (RSDs) of 0.9% to 10.5% and inter-day RSD of 0.7% to 12.2%, respectively. The calculated limits of detection and quantification were typically below 0.006 and 0.019 μg kg−1 for GC-MS/MS. The results of the method validation confirm that this proposed method is easy and reliable for the determination of residues of strobilurin fungicides in fruits, vegetables and soil.

Soil Surfactant and Fungicide Influence on Soil Moisture, Disease Presence and Quality of ‘Champion’ Ultradwarf Bermudagrass Grown on a USGA Specified Constructed Rootzone in South Carolina, U.S.A.

Soil Surfactant and Fungicide Influence on Soil Moisture, Disease Presence and Quality of ‘Champion’ Ultradwarf Bermudagrass Grown on a USGA Specified Constructed Rootzone in South Carolina, U.S.A.

Using Soil-Applied Fungicides to Manage Phytophthora Crown and Root Rot on Summer Squash.

Phytophthora crown and root rot (Phytophthora capsici) of summer squash is especially difficult to manage because all commercial cultivars are highly susceptible to P. capsici. Producers have traditionally relied on foliar fungicide applications to control Phytophthora crown and root rot despite their limited efficacy. Soil fungicide applications, including via subsurface drip chemigation, have recently gained interest as a method of improving control of P. capsici infections. In this study, soil drenches and foliar applications of 11 fungicides were compared for control of Phytophthora crown and root rot of summer squash in replicated field and greenhouse trials. Fungicides were applied at 7-day intervals. Incidence (%) of plant death was assessed from 7 to 42 days post inoculation (dpi) in field trials. Crown rot severity was rated on a scale of 1 (no wilting) to 5 (plant death) from 5 to 21 dpi in greenhouse trials. Results of field and greenhouse trials were similar. Plant death of 'Cougar' following inoculation with P. capsici isolate 12889 occurred at all growth stages from first true-leaf to full maturity in field trials. Plant death 42 dpi differed significantly (P ≤ 0.0001) among fungicides and application methods. The fungicide-application method interaction also was significant. Some fungicides were ineffective regardless of application method. In general, soil drenches were more effective than foliar applications at limiting plant death but no treatment completely controlled disease symptoms. Mean plant death 42 dpi was 41% for soil drenches and 92% for foliar sprays. Drenches of fluopicolide, mandipropamid, or dimethomorph limited plant death to ≤10% and prevented yield loss associated with root and crown rot. Foliar applications generally did not reduce plant death compared with the untreated, inoculated control, and were unable to prevent yield loss in field trials. In greenhouse trials, crown rot severity differed significantly (P ≤ 0.0001) among fungicides, application methods, and cultivars when plants were inoculated with P. capsici isolate 12889 or SP98. Crown rot was less severe and disease progress was slower following soil drenches than foliar applications. Some fungicide treatments were more effective on 'Leopard,' which was less susceptible to P. capsici than 'Cougar.' Soil application methods, including soil drench and drip chemigation, should be evaluated when fungicides are registered for soilborne disease control, because these methods provide better control of Phytophthora crown and root rot than foliar application.

Enantioselective separation and simultaneous determination of fenarimol and nuarimol in fruits, vegetables, and soil by liquid chromatography–tandem mass spectrometry

A method for simultaneous enantioselective determination of fenarimol and nuarimol in apple, grape, cucumber, tomato, and soil was developed using liquid chromatography-tandem mass spectrometry. The enantioseparation results of the two fungicides through three different cellulose-based chiral columns are discussed. The influence of column temperature on the resolution of the enantiomers of the two fungicides was examined. Complete enantioseparation of the two fungicides' enantiomers was obtained on a cellulose tris(4-methylbenzoate) column (Lux Cellulose-3) at 25 °C using methanol and 0.1 % formic acid solution (80:20, v/v) as mobile phase. The linearity, matrix effect, recovery, and precision were evaluated. Good linearity was obtained over the concentration range of 1-500 μg L(-1) for each enantiomer in the standard solution and sample matrix calibration solution. There was no significant matrix effect in apple, grape, cucumber, or tomato samples, but signal suppression was typically observed with the soil extracts. The mean recoveries, repeatability, and reproducibility were 76.5-103 %, 2.1-9.0 %, and 4.2-11.8 %, respectively. The limit of quantification for enantiomers of the two fungicides in fruits, vegetables and soil was 5 μg kg(-1). Moreover, the absolute configuration of the enantiomers of fenarimol and nuarimol was determined from a combination of experimentally determined and predicted electronic circular dichroism spectra.

Optimization of matrix solid‐phase dispersion conditions for organic fungicides determination in soil samples

A simplified sample preparation method, based on the matrix solid-phase dispersion technique, is proposed for the sensitive determination of 15 organic fungicides in vineyard soils by gas chromatography-mass spectrometry (GC-MS). Under final working conditions, sieved samples (0.5 g) were blended and dispersed with 2 g of C18 and transferred to a polypropylene syringe containing 1 g of diatomaceous earth. Analytes were recovered using 10 mL of ethyl acetate, this extract was concentrated to 1 mL and fungicides determined by GC-MS, without additional cleanup. The method provided recoveries in the range from 74 to 122% for soils with total carbon contents up to 5.5% and it allowed the use of external standard as quantification technique. Inter-day precision, given as relative standard deviations, stayed between 3 and 13%, and the limits of quantification were comprised between 0.6 and 15 ng g(-1). Several fungicides were found in the top layer of vineyard soils with the highest detection frequency and maximum concentration corresponding to iprovalicarb. Some real samples were also submitted to pressurized liquid extraction. Measured concentrations were in excellent agreement with those obtained by matrix solid-phase dispersion, which reinforces the accuracy of the latter methodology.

Management of Macrophomina wilt in melons using grafting or fungicide soil application: Pathological, horticultural and economical aspects

Melon cultivation in the Yizre’el Valley of northern Israel is threatened by plant wilting that occurs toward harvest. Macrophomina phaseolina is the most common fungus isolated from the wilted plants. Disease management using grafted plants or soil application of fungicides to non-grafted melons during the growing season was studied. For the grafting experiments, two Ananas-type melons (Cucumis melo L.), cv. 6405 and Eyal, were grafted onto interspesific F1Cucurbita rootstock TZ-148 and transplanted at spacings of 60, 90, 120 and 180cm within rows in M. phaseolina infested soil to test their ability to cope with the disease and to evaluate the profitability of grafted plant cultivation at different spacings. Grafted plants did not wilt, compared to 80 and 70% wilting of non-grafted melon plants in experiments conducted in 2006 and 2008, respectively. Cultivation of grafted melons in infested soil for the local market was shown to be profitable, even with a 50% reduction in transplant number for a given area (120cm between transplants). In addition, selection of the right melon cultivar as scion was shown to be crucial to the success of the crop. In another set of experiments conducted in summer 2010 with non-grafted melon plants, application of the fungicides azoxystrobin alone or combined with chlorothalonil or medenoxam reduced disease incidence to 5% as compared to 45% in the untreated control. Disease management using both cultural and chemical approaches is discussed.

Regalia<SUP>®</SUP> Bioprotectant in Plant Disease Management

bacterial diseases, and mancozeb and mefenoxam in controlling downy mildew. To enhance soilborne disease control and increase emergence, multiple delivery methods can be used, such as seed treatment, soil drenches, irrigation applications, and dipping seedlings prior to transplanting. The successful commercialization of Regalia® is the result of extensive research into efficacy and formulations, demonstration of all application options for efficacy, and innovative marketing strategies. Integration of plant extracts in disease management programs can increase yields and quality, reduce fungicide resistance in pathogens, lower residue of synthetic fungicides in plants and soil, and protect human health and the environment.

Compatibility of a Trichoderma atroviride biocontrol agent with management practices of Allium crops

Trichoderma atroviride Karsten strain C52 populations were measured in agronomic soils in combination with soil organic amendments, a nitrogen fertiliser, fungicides and diallyl disulphide (DADS) (a Sclerotium cepivorum sclerotial germination stimulant). Trichoderma atroviride C52 populations did not proliferate 2 weeks after inoculation in sandy soils (4.7 × 10 2 cfu/g soil) compared with silt loam soils (1.1 × 10 6–5.7 × 10 7 cfu/g soil), however, the addition of two blended pellet products containing poultry manure and other organic nutrients or humic acid plus organic matter to the sandy soil enabled populations to proliferate well (1.1–1.3 × 10 5 cfu/g soil). In vitro, twice field rate applications of urea reduced in vitro Trichoderma atroviride C52 growth (spore germination, germ tube length and mycelial growth), however, T. atroviride C52 populations were less sensitive to field rate applications of urea in field soil. Overall, T. atroviride C52 populations were not adversely affected when exposed to any of the fungicide soil treatments tested (populations ranged from 1.7 × 10 5–1.1 × 10 8 cfu/g soil). Volatiles of DADS reduced T. atroviride C52 mycelial growth in vitro when DADS was applied to the medium at standard and twice recommended field rates but not at half field rate. No spore germination occurred under any of the DADS in vitro treatments compared with 100% spore germination in the control. However, when DADS was applied to soil 4, 6 and 8 weeks before application of T. atroviride C52, populations were unaffected. Based on these data, an application strategy for the use of a commercial formulation of T. atroviride C52 in an integrated white rot management programme for onions is proposed.

Simultaneous enantioselective determination of triazole fungicides in soil and water by chiral liquid chromatography/tandem mass spectrometry

The manuscript concerns the development and validation of a novel and sensitive multi-residue method for simultaneous enantiomeric analysis of 8 triazole fungicides (tetraconazole, fenbuconazole, epoxiconazole, diniconazole, hexaconazole, triadimefon, paclobutrazol, and myclobutanil) in soil and water using chiral liquid chromatography coupled with tandem mass spectrometry. The separation and determination were performed using reversed-phase chromatography on a cellulose chiral stationary phase, a Chiralcel OD-RH (150 mm × 4.6 mm) column, under isocratic conditions using a mixture of ACN-2 mM ammonium acetate in water (55/45, v/v) as the mobile phase at 0.45 mL/min flow rate. The effects of three cellulose-based columns and three amylose-based columns on the separation were also investigated. The QuEChERS (acronym for quick, easy, cheap, effective, rugged and safe) method and solid-phase extraction (SPE) were used for the extraction and clean-up of the soil and water samples, respectively. Parameters including the matrix effect, linearity, precision, accuracy and stability were undertaken. Under optimal conditions, the mean recoveries for all sixteen enantiomers from the soil samples were 76.4–108.1% with 2.6–12.0% intra-day relative standard deviations (RSD) and 4.2–14.1% inter-day RSD at 5, 25 and 50 μg/kg levels; the mean enantiomer recoveries from the water samples were 81.2–106.5% with 2.1–11.5% intra-day RSD and 3.4–13.6% inter-day RSD at 0.25, 0.5 and 2.5 μg/L levels. Coefficients of determination R 2 ≥ 0.9989 were achieved for all studied analytes in the soil and water matrix calibration curves within the range of 1.0–125 μg/L. The limits of detection (LOD) (S/N = 3) for all enantiomers in the soil and water were less than 1.0 μg/kg or μg/L, whereas the limit of quantification (LOQ) (S/N = 10) did not exceed 3.0 μg/kg or μg/L. The results of the method validation confirm that this proposed method is convenient and reliable for the enantioselective determination of the enantiomers of triazole fungicides in soil and water.

Ultrasonic or accelerated solvent extraction followed by U-HPLC-high mass accuracy MS for screening of pharmaceuticals and fungicides in soil and plant samples

Different veterinary pharmaceuticals are used in agricultural livestock becoming a source of environment contamination. Furthermore, no regulation exists for the concentration limits of pharmaceuticals in soil or water. Monitoring programs for environment contamination with pharmaceuticals are needed, requiring new sensitive and selective screening methods. The present study focuses on developing a method for the simultaneous scanning of forty-two compounds (pharmaceuticals, azole biocides and fungicides) in soil and plant material samples. For extraction purposes the use of ultrasonic assisted and accelerated solvent extraction (ASE) were compared. The extract was purified and concentrated by applying a solid phase extraction step followed by ultra-high-performance-chromatographic separation and accurate-mass spectrometric detection using Exacte Orbitrap technology (FWHM 50,000). The effects of the different extraction solvents and conditions on the extraction efficiency were tested. Although both extraction approaches are applicable the optimal extraction efficiency was obtained by applying accelerated solvent extraction using solvent mixtures containing acetone for soil and methanol for plant samples. An ASE process has been validated for the determination of selected pharmaceuticals and fungicides in soil and in plant material. The recoveries from soil samples were >70% for more than 68% of the compounds. The levels of detection were ≤10μgkg−1 for 93% of the compounds tested. The recoveries from plant material were >70% for 64% of the compounds tested. The levels of detection were ≤10μgkg−1 for 66% of the compounds. The developed method was used to screen soil and plant material collected throughout the Netherlands and oxytetracycline residues were detected.

Chemically Enhanced Phytoextraction of Lead-Contaminated Soils

The effects of the combined application of soil fungicide (benomyl) and ethylenediaminetetraacetic acid (EDTA) on lead (Pb) phytoextraction by ryegrass (Lolium perenne) were examined. Twenty-five pots of Pb-contaminated soil (200 mg Pb kg−1) were seeded with ryegrass and randomly arranged into the following treatments: (1) Control, (2) benomyl, (3) EDTA, (4) benomyl and EDTA (B+E), and (5) benomyl followed by an application of EDTA 14 days later (B…E). Chemicals were applied when plants had reached maximum growth. Plants were analyzed for foliage Pb concentration using inductively coupled argon plasma (ICAP) spectrometry. The synergistic effects of the combined benomyl and EDTA application (treatments 4 and 5) were made evident by the significantly (p < 0.05) highest foliage Pb concentrations. However, the foliage dry biomass was significantly lowest for plants in treatments 4 and 5. The bioaccumulation factor (BF) and phytoextraction ratio (PR) were highest for plants in treatment 5 followed by plants in treatment 4.

Synthesis and application of a novel molecularly imprinted polymer‐coated stir bar for microextraction of triazole fungicides in soil

The preparation, characteristics and application of a sorptive stir bar coated with molecularly imprinted polymer (MIP) using triadimefon as the template molecule are described here. Raw glass capillary was coated with MIP through chemical bonding. The synthesis method was effective and reproducible with the batch-to-batch RSD within 7.8%. Scanning electron micrographs of the stir bar revealed a highly porous coating with average thickness of 15 μm. The synthesized stir bar was proved to be highly stable in most of the solvent for use. Extraction performance showed the fabricated stir bar has excellent molecular recognition abilities for triadimefon and the structure-related compounds, such as triadimenol, diniconazole, flutriafol, hexaconazole, tebuconazole, paclobutrazol and uniconazole, and thus can be applied for simultaneous determination of these triazole fungicides from complex samples by coupling with high-performance liquid chromatography. The variables that influence extraction were optimized with 10.0 μg/L standard solutions of triazole fungicides, and the analytical method was established for the determination of triazole fungicides in soil. The detection limits were in the range of 0.14-0.34 μg/L, and the recoveries were from 86.7 to 114.6% for spiked soil sample.

Soil fungal pathogens and the relationship between plant diversity and productivity

One robust result from many small-scale experiments has been that plant community productivity often increases with increasing plant diversity. Most frequently, resource-based or competitive interactions are thought to drive this positive diversity-productivity relationship. Here, we ask whether suppression of plant productivity by soil fungal pathogens might also drive a positive diversity-productivity relationship. We created plant assemblages that varied in diversity and crossed this with a ± soil fungicide treatment. In control (non-fungicide treated) assemblages there was a strong positive relationship between plant diversity and above-ground plant biomass. However, in fungicide-treated assemblages this relationship disappeared. This occurred because fungicide increased plant production by an average of 141% at the lower ends of diversity but boosted production by an average of only 33% at the higher ends of diversity, essentially flattening the diversity-productivity curve. These results suggest that soil pathogens might be a heretofore unappreciated driver of diversity-productivity relationships.

Management of Monosporascus sudden wilt of melon by soil application of fungicides

Sudden wilt (vine decline) of melon caused by Monosporascus cannonballus is a problem in arid and semiarid regions worldwide. Preplanting soil disinfestation with methyl bromide, a common treatment for disease management, has been banned in many countries, raising the need for alternative disease-control measures. Soil fungicide application during the growing season is one possible treatment. Twelve fungicides were evaluated in vitro for M. cannonballus suppression, seven of those were evaluated under field conditions. The fungicides azoxistrobin, prochloraz and pyraclostrobin + boscalid exhibited high and similar efficacies in controlling sudden wilt disease under field conditions. Fludioxonil applied at high rates was also effective but was phytotoxic. Fluazinam, the first fungicide found capable of suppressing sudden wilt and one which has been used in Israel since 2000, was less effective. The results indicate that two applications of a fungicide during the short fall season should be sufficient for effective control of the disease. In the long spring season, at least three applications are needed to protect the melon crop. Melon fruits were examined for fungicide residues and only boscalid residues were found. This fungicide was therefore limited to the first application before fruit set.

Reduced efficacy of rovral and botran to control Sclerotinia minor in lettuce production in the Salinas Valley may be related to accelerated fungicide degradation in soil

Accelerated soil degradation with repeated application was suggested to be responsible for the lack of efficacy of commercial fungicides to control lettuce drop caused by Sclerotinia minor in the Salinas Valley in California. In 2000, a study was initiated in a field artificially infested with S. minor to evaluate the efficacy and degradation potential of four selected fungicides (i.e., Rovral, Botran, Switch, and Endura). Crisphead lettuce was direct-seeded twice a year (spring and fall season) from 2000 to 2002. Fungicides were applied at recommended label rates twice during each season. Disease incidence was evaluated in fungicide treatments and nontreated control plots weekly starting immediately after thinning until harvest, and areas under the disease progress curves (AUDPC) were compared between treatments from 2000 to 2002. Soil samples (0–15 cm) were collected at regular intervals during the spring and fall 2002 lettuce seasons, and analyzed for residual fungicide concentration. Disease progress and final disease incidence were significantly affected by the fungicide treatment, season, year and interactions among these factors ( p < 0.05). At the end of the three year experiment, up to 18 and 50% of the lettuce was infected by S. minor for the spring and fall seasons, respectively. Fungicide efficacy to control lettuce drop was highest for Endura, followed by Switch and Botran, and lowest for Rovral. Relative persistence in soils was lowest for Rovral and Botran, followed by Switch and Endura. In 2002, residual soil fungicide concentrations were 11% for Rovral and Switch, 23% for Botran, and 88% for Endura relative to their initial concentrations. Results of this study provide first evidence suggesting that reduced efficacy of lettuce drop control from Rovral and Botran in the Salinas Valley may be related to an accelerated degradation of these fungicides due to repeated application. However, insufficient fungicide persistence due to inherent properties of this sandy loam soil or the chemical structure of these fungicides can not be excluded. Both hypotheses deserve further investigation.

Effects of fungicides triadimefon and propiconazole on soil bacterial communities

The impact of fungicides triadimefon and propiconazole on soil bacterial populations from a strawberry field was investigated. Two fungicides were applied to the soil at concentrations of 10 mg/kg or 100 mg/kg with soil water contents 20.2% (fresh soil water content) or 26.0% (field capacity). Changes in bacterial communities were assessed using DNA extraction, polymerase chain reaction (PCR) amplification of the 16S rDNA and denaturing gradient gel electrophoresis (DGGE). High performance liquid chromatography (HPLC) was utilized to detect the residue of fungicides in soils. The results showed that propiconazole was more persistent than triadimefon in soils, and the two soil water contents did not cause significant differences in dissipation rates between the two fungicides. A high concentration of propiconazole could inhibit the existence of soil microbes while one of triadimefon might induce the microbial population in the first stage. From unweighted pair-group method using arithmetic averages (UPGMA) dendrograms, the effect of triadimefon and propiconazole at the two applied concentrations on a soil bacterial community could be long term. After triadimefon was applied for 60 days and propiconazole for 75 days, the compositions of microbial communities were not recovered. From the viewpoint of environmental protection, it was of significant importance to pay more attention not only to the residues of pesticide but also to the change in soil microbial communities.

Effect of carbendazim and pencycuron on soil bacterial community

Soil bacterial composition is used as one of the important indicators of negative effects of the use of pesticides in agriculture. Very little is known on the effects of fungicides, particularly carbendazim and pencycuron on soil bacterial community. In this study, laboratory experiments were conducted to examine the effects of various concentrations of carbendazim and pencycuron on diversity of bacterial community in soils collected from strawberry field and incubated at different temperature conditions. The degradation rate of fungicides both in sterile and non-sterile soils were also investigated. Residues of fungicides were measured using high performance liquid chromatography (HPLC) and the change in bacterial community was examined by comparing the 16S rDNA bands on patterns by denaturing gradient gel electrophoresis (DGGE). The dissipation of carbendazim was affected by concentration applied, whereas that of pencycuron was affected by both concentration applied and incubation temperature. The microbial community could recover to its previous composition after 126 days of cultivation with the application of 10 mg/kg of carbendazim but not with the application of a high concentration, 100 mg/kg, of pencycuron. From cluster analysis, the bacterial community structure showed approximately 50% similarity throughout the experimental period, which indicated that the soil microbiota composition was not stable throughout the 120 cultivation days.

Delivery of Chemical and Microbial Pesticides through Drip Irrigation Systems

Applying pesticides uniformly to the target area with drip irrigation systems is essential for achieving effectiveness of efficient insect or disease control and for the sustainability of a safe environment. The uniformity and recovery rate of water-soluble and insoluble materials of chemical and microbial pesticides with different physical properties discharged from emitters throughout driplines was evaluated. The materials were a water-soluble fluorescent tracer (BSF), a flowable water-dispersible insecticide (Imidacloprid), a suspendible microbial entomopathogenic fungus (EPF), a suspendible microbial soil fungicide (SF), and microbial entomopathogenic nematodes. Treatments also included three different flow capacities of emitters with nominally rated flow capacities of 1.9, 3.8, and 7.6 L h-1, respectively. Although all materials were readily deliverable through the drip irrigation system, the uniformity of the materials discharged varied with the material formulations and emitter flow capacity. For all emitter flow capacities, BSF had the lowest coefficient of variation, followed by nematodes, Imidacloprid, SF, and EPF. Conversely, the recovery rate of the five materials was in the reverse order. Emitter flow capacity affected the recovery rates of Imidacloprid and SF discharged from the emitters, but not of BSF, EPF and nematodes. Drip irrigation was demonstrated as a viable alternative for application of water-soluble and insoluble materials; however, the discharge rates of EPF and SF must first be determined to compensate for their non-uniformity of delivery and low recovery rates from emitters.

Fungicide soil application efficiency for the control of black scurf (Rhizoctonia solani) on three potato cultivars

Fungicide soil application efficiency for the control of black scurf (Rhizoctonia solani) on three potato cultivars

Effect of Biocompost-Amendment on Degradation of Triazoles Fungicides in Soil

Soil amendments play an important role in management of pesticide residues. Present study reports the effect of biocompost-amendment on degradation of penconazole and propiconazole (triazole fungicides) in a sandy loam soil under flooded and nonflooded (60% water holding capacity) conditions. Penconazole degraded at faster rate than propiconazole. Both the fungicides were found to be more persistent in flooded soil than nonflooded soil, but application of biocompost at 2.5% and 5.0% levels enhanced their degradation under both moisture regimes.