Rates Of Fungicides Research Articles

Sensitivity of the pathogen of barley brown rust (<i>Puccinia hordei</i> G.H. Otth.) to fungicides – derivatives of triazoles and strobilurins

The sensitivity of the North Caucasian population of the pathogen of barley brown rust (Puccinia hordei G.H. Otth.) to fungicides derived from triazoles and strobilurines (preparations Amistar Gold, SK; Amistar Extra, SK; Baliy, KME; Delaro, KS) was determined. The work was carried out under controlled conditions of the greenhouse complex of the Federal National Research and Development Fund on winter barley of the susceptible Vivat variety of the Agricultural Scientific Center “Donskoy”. Winter barley plants in the germination phase were infected with the North Caucasian population of the barley brown rust pathogen. Fungicide treatment was carried out at the first signs of the disease with application rates of 0 (control, without treatment), 50, 100, 150 and 200% (the recommended application rate is assumed to be 100%). It was found that when treating infected barley plants with the fungicide Baliy, KME with different application standards, the biological effectiveness varied from 87.3 to 100%, Delaro, KS – from 78.1 to 100%, Amistar Extra, SK – from 79.2 to 100%, Amistar Gold, SK – from 85.3 to 100%. The use of the recommended dose of treatment(100%) contributed to a decrease in the development of brown rust in all variants by more than 96.9%. When using increased rates of fungicides (150, 200%), the biological efficiency was 100%. The high sensitivity of the North Caucasian population of the pathogen P. hordei to the active substances of the studied fungicides has been proven. For all the studied drugs, the values of LC50 and LC95 were significantly lower in comparison with the recommended concentration in the working solution. The result obtained was due to the content of active substances in fungicides from different chemical classes with different mechanisms of action, which provided high efficiency in suppressing the development of barley brown rust and reduced the risk of resistance.

Efficient and practical in-jar silicone rubber based passive sampling for simultaneous monitoring of emerging fungicides in water and soils

The occurrence and ecological impacts of emerging fungicides in the environment has gained increasing attention. This study applied an in-jar passive sampling device based on silicone rubber (SR) film to measuring the freely dissolved concentration (Cfree) of 6 current-use fungicides as a critical index of bioavailability in water and soils. The kinetics parameters including SR-water, soil-water, and organic carbon-water partition coefficients and sampling rates of the target fungicides were first attained and characterized well with their physicochemical properties. The in situ and ex situ field deployment in Hefei City provided the assessment of contaminated levels for these fungicides in rivers and soils. The Cfree of triadimefon and azoxystrobin was estimated at 0.54 ± 0.07–17.4 ± 2.5 ng L−1 in Nanfei River and Chao Lake, while triadimefon was only found in Dongpu Reservoir water with Cfree below 0.66 ± 0.04 ng L−1. The results exhibited that the equilibrium duration of 7 d was suitable for water application but a longer interval of 14 d was recommended for soil sampling. This work demonstrated the advantages of the proposed strategy in terms of fast monitoring within 2 weeks and high sensitivity down to detection limits in 0.5–5 ng L−1. The in-jar passive sampling device can be extrapolated to the evaluation for a wide coverage of organic pollutants in water and soils.

Management of Rust in Wheat Using IPM Principles and Alternative Products

Overall, there is a major wish that European farmers implement integrated pest management (IPM), particularly to reduce dependence on pesticides. In the European Rustwatch project, partners conducted nineteen trials across nine different countries during 2020 and 2021 to investigate different IPM strategies, focusing on controlling rust diseases in winter wheat. The trials included the use of varieties with contrasting levels of resistance, variety mixtures, reduced fungicide rates, thresholds, and Decision Support Systems (DSSs), and testing alternative products to fungicides. Sixteen trials developed yellow rust (Puccinia striiformis f. sp. tritici) infections, and six trials developed brown rust (Puccinia triticina) infections. Resistant varieties proved highly effective in keeping down yellow rust infection, and variety mixtures also effectively reduced infection levels and stabilized yields. Rust was fully controlled using 25% of standard fungicide rates, even under high disease pressure. Using DSSs provided sufficient control of rust diseases and resulted in competitive net economic returns due to fewer fungicide applications. The alternative products tested included two biological control agents and four alternative chemistries, which all gave inferior and insufficient control against rust compared with chemical fungicides. The trial work demonstrated that there are good and reliable options for including IPM into disease control in wheat.

Intense pulsed light for inactivating planktonic and biofilm molds in food.

It has been reported that about a quarter of the world's agriculture products is unable to be consumed each year because of mold contamination, resulting in incalculable economic losses. Despite modern food technology and the various preservation techniques available, the problem of mold contamination of food is still not adequately controlled. In this study, we simulated the biofilm formed by Aspergillus niger and Penicillium glaucum in liquid and solid food in 96 well cell culture plates and polycarbonate membrane models, respectively, and investigated the fungicidal effect of IPL on planktonic and biofilm molds at three different capacitance parameters at room and refrigerator temperatures. The results show that IPL can achieve fungicidal rates of over 99% for planktonic molds and over 90% for biofilm molds, and that the smaller the capacitance, the more frequent the irradiation required to achieve the same fungicidal rate. In addition, temperature, A. niger or Penicillium glaucum have no effect on the fungicidal effect of IPL. We believe that IPL is a promising non-thermal physical sterilization technique for fungal inhibition on food surfaces.

Effect of growth regulators on nonspecific resistance to fruit rot and peach yield

In peach cultivation, a major problem arises in protecting the plants from a complex of diseases that have a negative effect on their performance. Тhese include fruit rots caused by the fungi Botrytis cinerea Pers. and Moninia laxa (Aderh. & Ruhland) Honey. Тhe conventional method of protection against fruit rot involves the application of chemical pesticides, whose repeated use over several years causes environmental damage to agrocenosis and induces resistance in pathogens. To reduce the pesticide load in peach orchards, the use of growth regulators that have a stimulating and immunising effect has become an important trend. Here, the effects of Zerebra Agro, BP and Biosil, BE on peach resistance to fruit rots and yield were studied, when applied both as pure agents and in a spraying mixture containing half rates of fungicides. Тhe research was carried out in peach orchards (Red Haven variety) at the Federal Research Centre “Subtropical Science Centre of RAS” (Sochi, Russia) in 2020–2021, following standard methods. Тhe effect of growth regulators was evaluated at a moderate intensity of infestation by fruit rot (intensity of grey rot and moniliosis amounted to 24.6–25.1 and 22.5–23.6 %, respectively). In the two-year experiment, the rate of grey rot and moniliosis was reduced (4.1–8.6 % for grey rot and 5.0–8.6 % for moniliosis). Тhe agent Albit, TPS in a spraying mixture containing half of the fungicides showed a biological efficiency of 72.7–78.8 %. Тhe biological efficiency of Zerebro Agro, VP amounted to 68.8–83.3 % (with fungicides in a spraying mixture) and 69.0–76.8 % (pure agent). With the application of growth regulators, peach yields varied between 57–87 centner/ha, giving an improvement of 135.7–212.2% over the control.

A Secondary Metabolite Secreted by Penicillium citrinum Is Able to Enhance Parastagonospora nodorum Sensitivity to Tebuconazole and Azoxystrobin.

Parastagonospora nodorum causes glume and leaf blotch of wheat, a harmful disease resulting in serious losses in grain yield. In many countries including Russia, fungicidal formulations based on triazoles and on triazoles combined with strobilurins are used to control this fungus. However, their prolonged application may promote the selection of fungicide-resistant strains of P. nodorum leading to significant attenuation or even loss of fungicidal effect. Chemosensitization of plant pathogenic fungi with natural compounds represents a promising strategy for mitigating fungicide resistance and other negative impacts of fungicides. In this work, we applied a chemosensitization approach towards P. nodorum strains non-resistant or resistant to tebuconazole or azoxystrobin using 6-demethylmevinolin (6-DMM), a metabolite of Penicillium citrinum. The resistant strains were obtained by the mutagenesis and subsequent culturing on agar media incorporated with increasing doses of Folicur® EC 250 (i.e., tebuconazole) or Quadris® SC 250 (i.e., azoxystrobin). Test strains m8-4 and kd-18, most resistant to tebuconazole and azoxystrobin, respectively, were selected for sensitization experiments. These experiments demonstrated that combining 6-DMM with Folicur® enhanced fungicidal effectiveness in vitro and in vivo in addition to attenuating the resistance of P. nodorum to tebuconazole in vitro. 6-DMM was also found to augment Quadris® efficacy towards kd-18 when applied on detached wheat leaves inoculated with this strain. Experiments on P. nodorum sensitization under greenhouse conditions included preventive (applying test compounds simultaneously with inoculation) or post-inoculation spraying of wheat seedlings with 6-DMM together with Folicur® at dose rates (DR) amounting to 10% and 20% of DR recommended for field application (RDR). Combined treatments were run in parallel with using the same DR of the fungicide and sensitizer, alone. A synergistic effect was observed in both preventive and post-inoculation treatments, when the sensitizer was co-applied with the fungicide at 10% of the RDR. In this case, disease reduction significantly exceeded the protective effect of Folicur® at 10% or 20% of the RDR, alone, and also a calculated additive effect. Collectively, our findings suggest that 6-DMM is promising as a putative component for formulations with triazole and strobilurin fungicides. Such new formulations would improve fungicide efficacy and, potentially, lower rates of fungicides needed for plant pathogen control.

Trichoderma species isolated from grapevine with tolerance towards common copper fungicides used in viticulture for plant protection.

Copper-containing fungicides are applied broadly in organic viticulture against downy mildew caused by Plasmopara viticola. Although long-term application of copper-based fungicides is associated with ecotoxic effects on the environment, their use in viticulture is required until sustainable alternatives are available. Trichoderma spp. might be a promising approach to fungicide reduction while promoting plant growth and development and displaying biocontrol activity. This study aims to examine the tolerance and compatibility of Trichoderma spp. to copper fungicides. This work contributes to the development of a spray application consisting of a copper-tolerant Trichoderma sp. combined with a downscaled copper fungicide rate against P. viticola. Trichoderma spp. isolated from grapevine wood in vineyards were identified and used for tolerance screening in various concentrations of copper fungicides. Copper hydroxide was identified as being highly compatible with Trichoderma. Two Trichoderma candidates, T. koningiopsis and T. harzianum, showed high copper tolerance in mycelial growth and germination tests, and were adapted to 2.85 g Cu L-1 of the selected fungicide. Microscopic investigations showed the attachment of copper compounds to fungal cell walls and copper uptake within the cytoplasm. In the case of high tolerance, large-scale copper uptake was prevented. Our findings identified two highly copper-tolerant Trichoderma isolates with natural adaptation to the vineyard ecosystem, which could be further tested as biostimulants and biocontrol agents, combined with a reduced fungicide rate for sustainable plant protection. © 2022 Society of Chemical Industry.

Antifungal activity of an artificial peptide aptamer SNP-D4 against Fusarium oxysporum.

Fusarium oxysporum f. sp. cubense (FOC4) is a pathogen of banana fusarium wilt, which is a serious problem that has plagued the tropical banana industry for many years. The pathogenic mechanism is complex and unclear, so the prevention and control in agricultural production applications is ineffective. SNP-D4, an artificial peptide aptamer, was identified and specifically inhibited FOC4. To evaluate the efficacy of SNP-D4, FoC4 spores were treated with purified SNP-D4 to calculate the germination and fungicide rates. Damage of FOC4 spores was observed by staining with propidium iodide (PI). Eight proteins of FOC4 were identified to have high affinity for SNP-D4 by a pull-down method combined with Q-Exactive mass spectrometry. Of these eight proteins, A0A5C6SPC6, the aldehyde dehydrogenase of FOC4, was selected as an example to scrutinize the interaction sites with SNP-D4. Molecular docking revealed that Thr66 on the peptide loop of SNP-D4 bound with Tyr437 near the catalytic center of A0A5C6SPC6. Subsequently 42 spore proteins which exhibited associations with the eight proteins were retrieved for protein-protein interaction analysis, demonstrating that SNP-D4 interfered with pathways including ‘translation’, ‘folding, sorting and degradation’, ‘transcription’, ‘signal transduction’ and ‘cell growth and death’, eventually causing the inhibition of growth of FOC4. This study not only investigated the possible pathogenic mechanism of FOC4, but also provided a potential antifungal agent SNP-D4 for use in the control of banana wilt disease.

A fractional mathematical modeling of protectant and curative fungicide application

Fungicides are consumed to foreclose or slow the epidemics of disease germ by fungi. Crop cultivation is a favorable business platform for farmers, but it is also very common for them to have losses. These losses happen by attacking pathogens, such as fungi, oomycetes (water fungi), viruses, bacteria, nematodes, and viroid that spread the infection into the plants. In this article, we derive a fractional mathematical model for simulating the dynamics of fungicide application via Caputo-Fabrizio fractional derivative. Caputo-Fabrizio operator is defined with non-singular type kernel which is better than singular kernel. We give some important proofs related to the existence of a unique solution of the given model. We derive the solution of the model by using the Adams-Bashforth algorithm and also mentioned the stability of the method. We plotted the number of graphs at different fungicide application rate, fungicide decay rate, fungicide effectiveness, curatives rate of fungicide, growth rate of the host, and removal rate. A complete structure of the given problem can be understood by this paper. The main novelty of this work is to understand the role of fungicide application in the disease caused by fungi with the help of fractional derivatives consisting memory effects.

Evaluation of Varying Rates of Mancozeb fungicide and Some Plant Leaf Powders as Seed Treatment and their cost-benefit for the Management of Early Leaf Spot (Cercospora arachidicola Hori) Disease of Groundnut in Makurdi, Nigeria

Field experiment were carried out during the first and second cropping seasons (2013//2014) at the Teaching and Research Farm of the Federal University of Agriculture Makurdi, Benue State of Nigeria, the effect of seed treatments with varying rates of Mancozeb fungicide, Pawpaw and Moringa leaf powders on early leaf spot incidence and ground nut yield was studied; and the cost benefit ratios calculated. The seed treatments were: Mancozeb, Moringa leaf powder and Pawpaw leaf powder while the seed treatments rates were 0.0 (control), 2.0, 2.5 and 3.0gm. Groundnut variety Benue AGR seeds were treated with the seed treatment rates replicated 3 times and arranged in a randomized complete block design (RCBD). Results of the first season and second seasons showed that seed treatment with Mancozeb significantly gave the highest plant establishment followed by moringa leaf powder and pawpaw leaf powder respectively. In the first year, 3.0g seed treatment significantly gave the highest plant establishment while the untreated control recorded the lowest plant establishment, but was not significantly difference (P ≤ 0.05) amongst the treatment rates in the second year. In the two cropping seasons, plants grown from seed treated with mancozeb recorded the lowest incidence of early leaf spot disease followed by moringa leaf powder at 40, 47 and 54 DAS respectively. Seed treatment rate of 3.0gm gave the lowest disease incidence from 40 to 54 DAS. At 90 DAS of the first season, seed treatment with Mancozeb significantly lowered the leaf defoliation followed by Moringa leaf powder compared to Pawpaw leaf powder. Similarly, during the second season, seed treatment with Mancozeb also reduced the leaf defoliation compared to the plant powders at 70, 80 and 90 DAS respectively. Mancozeb and Moringa leaf powder gave higher grain yield compared to Pawpaw leaf powder in the first season. Increase in seed treatment rate resulted to higher percentage increment in grain and haulm ............

Progression of chocolate spot (Botrytis fabae) and grain yield of faba bean as influenced by integration of fungicide rate and host resistance in Southern Ethiopia

Progression of chocolate spot (Botrytis fabae) and grain yield of faba bean as influenced by integration of fungicide rate and host resistance in Southern Ethiopia

The Residual Behavior of Chlorothalonil and Metalaxyl in The Egyptian Cucumbers Fields Infested with Downy Mildew Using The High-Performance Liquid Chromatography (Hplc) and Quechers Method. سلوک متبقيات الکلوروثالونيل والميتالاکسيل فى حقول الخيار المصابه بالبياض الزغبى بإستخدام جهاز الکروماتوجراف السائل عالى الأداء HPLC)) بإستخدام طريقة الـQUECHER.

The dissipation rate of the commercial fungicide with two active ingredients (Chlorothalonil 64% + Metalaxyl 8%) that was approved by the agriculture pesticides committee was evaluated in the cucumber fields infested with downy mildew in Egypt using HPLC analytical system. The experiment was designed in randomized block design. After spraying at the recommended rate of applications, the samples of cucumber were chosen randomly from treated and un-treated plants after the interval of zero time(2hours), 1, 3, 7,10, and 14 days. The technique was validated at different fortification levels (0.01, 0.5, and 0.1 μg mL−1). The recoveries of both fungicides Chlorothalonil and Metalaxyl were 87.6 and 95 %. The results showed that the initial residues (zero time) were 4.38and 3.21 mg/kg-1. All detected residues significantly decreased upon time elevated. The residues extracted by an optimized QuEChERS coupled with HPLC analytical system were accurate and acceptable The limit of quantitation was 0.05 for both fungicides. The dissipation curves of both Chlorothalonil and Metalaxyl followed the first-order kinetics. The half-life’s (t½) values were 0.89 and 1.1days in, respectively. Under the optimized condition, the residues of Chlorothalonil and Metalaxyl in cucumber were below the codex maximum residue limit (0.5 and 3 mg/kg-1). Consequently, the pre-harvest intervals (PHI) in cucumber were seven days for the fungicide.

Smallholder Coffee Productivity as Affected by Socioeconomic Factors and Technology Adoption

Despite the increase in area under coffee in Kenya in the last decade, productivity has been on the decline. Numerous production technologies have been developed through on-station research but there has been limited on-farm research to assess the impact of these technologies at the farm level. On the other hand, smallholder farmers are endowed differently and this would positively or negatively affect the adoption of recommended technologies and hence coffee productivity. This study was carried out to evaluate the effects of socioeconomic factors and technology adoption on smallholder coffee productivity at the farm level. The study employed stratified random sampling where 376 farmers were randomly sampled from six cooperative societies which had been preselected using probability proportional to the size sampling technique. The effects of socioeconomic factors and technology adoption on coffee productivity were analyzed using the stochastic Cobb-Douglas production function. The study revealed that off-farm income, access to credit, type of land tenure, and land size had significant positive effects on coffee productivity. Therefore, coffee farmers should be encouraged to diversify their income sources and to embrace credit financing, as the government reviews land use policies to avail adequate agricultural land. The study further revealed that the adoption of recommended application rates of manure, fungicides, and pesticides had significant positive effects on coffee productivity. The adoption of these technologies should therefore be enhanced among small-scale farmers to improve coffee productivity at the farm level.

Rate and Spraying Frequency Determination of Propiconazole Fungicide for the Management of Garlic Rust at Woreilu District, Northeastern Ethiopia

Rust is a major disease of garlic in Ethiopia. A field experiment was conducted at Kabe and Segno Kebeles of Woreilu District in 2019 to determine the appropriate rate and spraying frequency of propiconazole fungicide and select cost-effective management options of garlic rust. A randomized complete block design with three replications was used. The combination of five rates and three spraying frequencies of propiconazole fungicide and unsprayed treatments was evaluated. A combination of rate and spraying frequencies of propiconazole significantly reduced disease with correspondingly increased bulb yield of garlic. The minimum percentage severity index and area under disease progress curve were scored from plots treated by all rates with three times spraying frequency of Tilt fungicide application. The highest bulb yield was obtained from plots treated with all fungicide rates with three times spraying frequencies of propiconazole application. But the highest (6896.36%) marginal rate of return was obtained from plots treated with 0.5 L with two times spraying. Generally, 0.5 liters with two times spraying of propiconazole was effective in controlling garlic disease and get the highest cost-benefit advantage as compared with other treatments. Therefore, it could be recommended for the management of garlic rust in Ethiopia.

Assessment of the silicon compounds effect on disease resistance and productivity of spring barley with a decrease in pesticide load in the south of Russia

In a small-plot field experiment, the effect of different forms of silicon compounds (tetraethoxysilane (TES) and sodium silicate) and processing methods (seeds and plants) on disease incidence and productivity of spring barley varieties was studied and the effect of diseases on productivity was evaluated. It was found that the use of silicon-containing compounds separately and in a mixture with a reduced consumption rate of fungicide led to a decrease in the infestation of barley with root rot and leaf spots. The lowest degree of disease development was observed when using a fungicide and mixtures of TES and sodium silicate with a reduced consumption rate of fungicide. The maximum yield increases were obtained by combining two types of treatment with silicon - seeds and plants. When processing seeds, the use of sodium silicate was more effective. The relationship between the development of diseases and the productivity of spring barley, primarily grain biomass, is estimated in most cases as strong and medium.

Quinone outside inhibitor-resistant Colletotrichum nymphaeae isolates from strawberry lack mutations in cytb gene

Anthracnose fruit rot is one of the main diseases affecting strawberries especially in warm and humid climates. In commercial settings, producers are relying on fungicides to control the disease. One of the most potent chemical classes of fungicides for anthracnose control are the quinone outside inhibitors (QoIs), but resistance in field isolates due to a point mutation in the target gene cytb has recently been reported in multiple states of the USA. During a routine screening, two Colletotrichum nymphaeae isolates (OH_S1 and OH_S2) obtained from strawberry plants of a commercial field in Marietta-Ohio were found to be resistant to QoI fungicide azoxystrobin. The EC50 values determined in poison agar tests were greater than 100 μg/L. Both isolates were not controlled on detached strawberry fruit treated with label rates of Abound fungicide (a.i. azoxystrobin) and revealed disease severity of 86% and 96% on detached fruit. A baseline isolate (Cn_ebel2) of the same species revealed an EC50 value of 1.2 μg/L and no disease developed on Abound-treated fruit. In contrast to other reports, sequencing of the cytb gene from all three isolates used in this study revealed no amino acid changes in cytb, indicating the existence of a different and still unknown resistance mechanism.

Sensitivity of Colletotrichum acutatum Isolates from Citrus to Carbendazim, Difenoconazole, Tebuconazole, and Trifloxystrobin.

Postbloom fruit drop (PFD) of citrus is caused by the Colletotrichum acutatum and C. gloeosporioides species complexes. The disease is important when frequent rainfall occurs during the flowering period of citrus trees. In Brazil, until 2012, PFD was mainly controlled by preventive applications of the methyl-benzimidazole carbamate (MBC) carbendazim and demethylation-inhibitor (DMI) fungicides such as difenoconazole. Since then, mixtures containing the DMI tebuconazole and the quinone-outside inhibitor (QoI) trifloxystrobin have been commonly used. Fungicides are often applied preventively, sometimes even when conditions are not conducive for PFD development. Excessive fungicide applications may favor the selection of resistant populations of Colletotrichum spp. In this study, we assessed the fungicide sensitivity of C. acutatum isolates collected during the two distinct periods of PFD management in Brazil: before and after the trifloxystrobin and tebuconazole mixture became widely employed. The sensitivity of 254 C. acutatum isolates to carbendazim and difenoconazole and of 164 isolates to tebuconazole and trifloxystrobin was assessed. Mycelial growth inhibition of these isolates was evaluated for all the fungicides using either serial dilution of fungicide rates or the spiral gradient dilution method. In addition, inhibition of conidial germination was also assessed for trifloxystrobin. Analysis of partial β-tub, cytb, and cyp51b gene sequences did not reveal any mutations related to resistance to MBCs, QoIs, and DMIs, respectively. In mycelial growth assays, mean EC50 values were 0.14, 0.11, and 0.21 μg/ml for difenoconazole, tebuconazole, and trifloxystrobin, respectively. The conidial germination inhibition by trifloxystrobin was similar among the tested isolates, and the mean EC50 value was 0.002 μg/ml. All isolates had similar mean mycelial growth inhibition for carbendazim, regardless of the fungicide concentrations. Therefore, based on similar EC50 values and molecular analyses, no shift in the sensitivity of isolates has been observed to the fungicides commonly used in different citrus-producing areas in Brazil.

High Levels of Insensitivity to Phosphonate Fungicides in Pseudoperonospora humuli.

Phosphonate (phosphite; HPO3-2) is fungicidal against oomycetes and certain other organisms. The Fungicide Resistance Action Committee has deemed phosphonate to be at low risk of resistance development, and reduced sensitivity to phosphonate has been reported only occasionally in plant pathogens. Reduced sensitivity to the fungicide fosetyl-Al was documented in the hop downy mildew pathogen, Pseudoperonospora humuli, in the early 2000s, but disease caused by insensitive isolates could still be managed commercially if the fungicide rate was doubled from 2.24 to 4.48 kg/ha. In this research, we document the occurrence of isolates of P. humuli in Oregon that possess even higher levels of insensitivity to fosetyl-Al and other phosphonate fungicides. The median estimated effective concentration required to reduce infection by 50% (EC50) for isolates collected from two farms reporting disease control failures was 2.7% (vol/vol) phosphonate (range = 1.6 to 164.2), which was 1.6 times (range = 0.9 to 96.0) the maximum labeled rate of the phosphonate fungicide utilized. In contrast, the median EC50 for isolates obtained from experimental plots that have received only a single application of a phosphonate fungicide was 0.6% (vol/vol) phosphonate (range = 0.11 to 2.3) or 0.3 times the maximum allowable rate. Sensitivity of isolates to a phosphorous acid fungicide, fosetyl-Al, and a plant nutrient product containing an unspecified level of phosphorous acid were linearly related. Insensitivity to the maximum allowable rate of a phosphorous acid fungicide was widespread within and among hop farms in Oregon. Among 54 isolates assayed for phosphonate insensitivity, 96% had EC50 values that exceeded the maximum allow rate of the fungicide used in the assays. Field studies conducted in 2 years further demonstrated that a phosphorous fungicide, a nutrient product containing phosphorous acid, and fosetyl-Al failed to provide commercially acceptable suppression of downy mildew when applied at the maximum allowable rates and even double these rates, whereas fungicides with different modes of action provided 91% or greater disease control. The whole of this research indicates that P. humuli has been selected to tolerate fosetyl-Al and other phosphonate fungicides at rates four times greater than those used earlier to obtain satisfactory suppression of downy mildew. This finding has implications for management of the disease not only in Oregon but also, in other production regions should insensitive isolates be introduced on infected planting material.

Control of avocado white root rot using non-pathogenic Rosellinia necatrix isolates combined with low concentration of fluazinam

Different studies to control the Rosellinia necatrix growth in vitro and avocado white root rot in vivo were performed, using two non-pathogenic R. necatrix isolates (Rn12 and Rn29) combined with fluazinam. The application of non-pathogenic isolates alone showed significant growth reduction as compared to R. necatrix pathogenic isolates in a PDA growth medium. The combination of both non-pathogenic isolates plus fluazinam at 0.01 mg l−1 significantly increased the reduction of the pathogen growth in vitro. Additionally, the combination of the lowest fluazinam concentration (0.001%) plus Rn12 improved control of the disease as compared when either the same fungicide rate was used alone or this isolate was applied alone on plants, showing a similar response to the use of the highest concentration of fluazinam applied alone (0.01%). In this work, we have obtained a new, integrated biological control method against this avocado disease using non-pathogenic R. necatrix isolates combined with low doses of fluazinam.

Эффективность микробиологических препаратов на основе Bacillus subtilis и Trichoderma harzianum в защите ярового ячменя от болезней на Северо-Западе России

The efficacy of microbiological plant protection specimens based on Bacillus subtilis (Vitapan, SP) and Trichoderna harzianum (Trikhotsin, SP) was studied on such spring barley diseases as a root rot and Helminthosporium leaf spot. The use of these biological products in the treatment of seeds and vegetative plants of spring barley was ineffective, namely a decrease in the development of root rot and helminthosprium disease did not exceed 35%. A greater protective effect was achieved when using studied preparations for treating seeds with a low degree of infection with the main pathogen of root rot. The use of Vitaplan in a tank mixture with reduced consumption rates of the chemical fungicides was less effective than pure chemicals with full consumption rates: the decrease was 17% for root rot and 12.7% for Helminthosporium leaf spot. Thus, it is advisable to use mixtures of chemicals with the Vitaplan as a biological for treatment of seeds with an average degree of infection by root rot pathogens and a predicted moderate development of Helminthosporium disease. spring barley, biological plantprotecting agents, root rot, protective efficiency.