Association of hydrogen peroxide with commercial fungicide formulations in the control of Asian soybean rust

ABSTRACT: In recent years, there have been reductions in the efficacy of the fungicidal control of Phakopsora pachyrhizi, thereby hindering the management of soybean rust and compromising crop yield. This study evaluated the effects of incorporating hydrogen peroxide (H2O2) in commercial fungicide formulations on the control of soybean rust. We conducted two experiments, one of which was performed in a greenhouse environment and the other under field conditions. In both environments, we examined the following four control programs using commercial fungicide formulations: (I) azoxystrobin + cyproconazole (quinone outside inhibitor [QoI] + demethylation inhibitor [DMI]); (II) picoxystrobin + cyproconazole (QoI + DMI); (III) pyraclostrobin + epoxiconazole + fluxapyroxad (QoI + DMI + succinate dehydrogenase inhibitor); and (IV) water (H2O) (program without fungicide application), combined with the incorporation of (i) H2O2; (ii) mancozeb (positive control I); (iii) chlorothalonil (positive control II); or (iv) water (H2O) alone. Analyses of infected leaf area and grain yield revealed that the addition of H2O2 to the formulations of DMI and QoI fungicides led to a reduction in disease severity of between 33% and 44% relative to the effects of these products used alone, as well as an increase in yield and SPAD values. The use of H2O2 and multi-site fungicides alone failed to provide effective control of soybean rust. In addition to enhancing the efficacy of disease control, the use of H2O2 associated with commercial fungicide mixtures was shown to be a potential tool for the management of fungicide resistance and reduction in losses from Asian soybean rust.

Co-formulant in a commercial fungicide product causes lethal and sub-lethal effects in bumble bees

Pollinators, particularly wild bees, are suffering declines across the globe, and pesticides are thought to be drivers of these declines. Research into, and regulation of pesticides has focused on the active ingredients, and their impact on bee health. In contrast, the additional components in pesticide formulations have been overlooked as potential threats. By testing an acute oral dose of the fungicide product Amistar, and equivalent doses of each individual co-formulant, we were able to measure the toxicity of the formulation and identify the ingredient responsible. We found that a co-formulant, alcohol ethoxylates, caused a range of damage to bumble bee health. Exposure to alcohol ethoxylates caused 30% mortality and a range of sublethal effects. Alcohol ethoxylates treated bees consumed half as much sucrose as negative control bees over the course of the experiment and lost weight. Alcohol ethoxylates treated bees had significant melanisation of their midguts, evidence of gut damage. We suggest that this gut damage explains the reduction in appetite, weight loss and mortality, with bees dying from energy depletion. Our results demonstrate that sublethal impacts of pesticide formulations need to be considered during regulatory consideration, and that co-formulants can be more toxic than active ingredients.

Cinnamomum cassia essential oil and (E)-cinnamaldehyde as control agents of anthracnose on common bean seeds

Among the fungi that cause damage to the common bean and are disseminated by the seeds, Colletotrichum lindemuthianum (Sacc. e Magn.) Briosi e Cavara stands out. This fungus causes anthracnose in common bean ( Phaseolus vulgaris L.). Use of natural compounds is a viable and safer option than chemicals to manage this disease. Essential oils have shown antifungal potential against phytopathogenic fungi. According to the results of the in vitro test, we observed complete inhibition of the growth of C. lindemuthianum with the use of cassia cinnamon essential oil ( Cinnamomum cassia ) (EO) and its major component ( E )-Cinnamaldehyde, presenting MIC of 125 µg/mL, while the commercial fungicide presented MIC of 30.6 µg/mL. And in vivo , where seeds naturally infected with C. lindemuthianum were treated with the EO and the substance in a solution with commercial soybean oil, we observed that the treatments did not affect germination and initial seed vigor. In addition, the seed treatment with solutions formulated from EO and ( E )-cinnamaldehyde was efficient for reducing the incidence of anthracnose over the days evaluated, as well as for the commercial fungicide used (methyl thiophanate). This is the first study to demonstrate the efficacy of C. cassia oil and (E)-cinnamaldehyde in the control of C. lindemuthianum through the treatment of common bean seeds.

Efeito do ácido indolbutírico (AIB) no enraizamento de estacas herbáceas e lenhosas de serigueleira (Spondias purpurea L.)

The serigueleira is a fruit that is little explored commercially in several regions of Brazil, having little work regarding the feasibility of seedling production by cuttings with and without plant regulators. Due to this lack of technical information, the present work has as main objective to evaluate the rooting of herbaceous and woody cuttings of the serigueleira (Spondias purpurea L.) treated with indolbutyric acid (AIB). Herbaceous and woody cuttings were obtained from a matrix plant with approximately fifteen years of age, with 12 cm in length the cuttings were cut in bevel and then immersed in a commercial fungicide solution of 0.2%. The cuttings were treated with AIB in the form of talc, 0, 1%, 2%, 3% and 5%, planted in beds containing vermiculite, rice straw and construction sand. The experimental design used was completely randomized, with four replications, each plot consisting of 10 cuttings. Cuttings were evaluated over 90 days, recording the following parameters: percentage of rooted cuttings, percentage of live cuttings and calluses, number of cuttings with buds, average length of the largest root and number of roots. Among the results obtained, the best concentration was 3% of 5% IBA in the rooting of herbaceous cuttings (17,25% in 17,75%) and 5% of IBA in the rooting of woody cuttings (22,25% e 22,55%). Herbaceous cuttings showed higher percentages of cuttings with calluses when compared to woody cuttings.

Reduced Asian Soybean Rust Control by Commercial Fungicides Co-formulations in the 2018-2019 Growing Season in Southern Brazil

It has been a growers concen the reduction of Asian soybean rust (ASR) control by commercial fungicide co-formulations in the last growing seasons in southern Brazil. The objective of this work was to assess the ASR control efficacy by the most used co-formulations in the 2018/19 season. In a field experiment, 19 fungicides in commercial formulations to control soybean rust caused by Phakopsora pachyrhizi, were evaluated. Chemicals at their recommended doses were sprayed at four soybean growth stages. The first application was performed with 1.82% leaflet incidence and coinciding with R1 phenological stage. The others were performed at 14-18 days intervals. At stage R6, end of the epidemic and coinciding with half of the defoliation in the control plots, the leaf severity was appraised. The experiment was conducted with Ativa soybean cultivar, in 3 × 6 m plots, four replications and randomized block design. The harvest was made with a plot combine and the yield expressed in grains kg/ha. The means were compared by the Scott-Knott test. The disease control efficacy by 17 fungicide co-formulation showed control less than 57%, one with 78% and none with ≥ 80%. The unsprayed treatment severity was 81% and the greatest control of 78% resulted in 3,876 kg/ha yield. Therefore, the hypothesis raised in this work was accepted showing that the site-specific fungicides co-formulations are showing efficacy reduction season after season.

Antagonism of saprobe fungi from semiarid areas of the Northeast of Brazil against Sclerotinia sclerotiorum and biocontrol of soybean white mold

The antagonistic activity of 25 saprobe fungi from semiarid areas of Northeast Brazil was evaluated against Sclerotinia sclerotiorum (Lib.) de Bary (Helotiales: Sclerotiniaceae). Four fungi [Myrothecium sp. Tode (Hypocreales: Stachybotryaceae) isolate 2, Volutella minima Höhn. (Hypocreales: Nectriaceae), Phialomyces macrosporus P.C. Misra & P.H.B. Talbot (Pezizomycotina) and Dictyosporium tetraseriale Goh, Yanna & K.D. Hyde (Pleosporales: Dictyosporiaceae)] were selected and further tested their ability to inhibit mycelial growth, sclerotia formation and ascospore germination of S. sclerotiorum and to control white mold on soybean plants. V. minima and P. macrosporus filtrates at 50% effectively suppressed mycelial growth and Myrothecium sp. isolate 2 completely suppressed sclerotia formation and inhibited ascospore germination by over 95%, the same result as commercial fungicide fluazinam. Soybean plants pre-treated with Myrothecium sp. isolate 2, P. macrosporus, and V. minima and inoculated with S. sclerotiorum showed a reduction of 55.8%, 79.7%, and 83.2% of area under disease progress curve (AUDPC) of white mold, respectively, in relation to water. Collectively, these results underline the antagonistic activity of V. minima, P. macrosporus, and Myrothecium sp. isolate 2 against S. sclerotiorum and their potential as biocontrol agents of soybean white mold.

Cyclic Synthetic Peroxides Inhibit Growth of Entomopathogenic Fungus Ascosphaera apis without Toxic Effect on Bumblebees

In recent years, the number of pollinators in the world has significantly decreased. A possible reason for this is the toxic effects of agrochemicals reducing the immunity of insects that leads to their increased susceptibility to pathogens. Ascosphaera apis is a dangerous entomopathogenic fungus, afflicting both honeybees and bumblebees. We investigated fungicide activity of cyclic synthetic peroxides against A. apis isolated from Bombus terrestris L. The peroxides exhibited high mycelium growth inhibition of A. apis up to 94–100% at concentration 30 mg/L. EC50 values were determined for the most active peroxides. Two peroxides showed higher antifungal activity against A. apis than the commercial fungicide Triadimefon. The studied peroxides did not reduce the ability of bumblebees to fly and did not lead to the death of bumblebees. A new field of application for peroxides was disclosed.

Synthesis, crystal structure and biological activity of copper(II) complex with 4-nitro-3-pyrazolecarboxylic ligand

The reaction of 4-nitro-3-pyrazolecarboxylic acid and Cu(OAc)2?H2O in ethanol resulted in a new coordination compound [Cu2(4-nitro-3- -pzc)2(H2O)6]2H2O (4nitro-3pzc = 4-nitro-3-pyrazolecarboxylate). The compound was investigated by means of single-crystal X-ray diffraction and infrared spectroscopy. The biological activity of the complex was also tested. In the crystal structure of [Cu2(4nitro-3-pzc)2(H2O)6]2H2O, the Cu(II) ion is in a distorted [4+2] octahedral coordination due to the Jan?Teller effect. A survey of the Cambridge Structural Database showed that the octahedral coordination geometry is generally rare for pyrazole-bridged Cu(II) complexes. In the case of Cu(II) complexes with the 3-pyrazolecarboxylato ligands, no complexes with a similar octahedral coordination geometry have been reported. Biological research based on determination of the inhibition effect of the commercial fungicide Cabrio top and the newly synthesized complex on Ph. viticola were performed using the phytosanitary method.

Design, Synthesis and Biological Evaluation of N-((2-phenyloxazol-4-yl)methyl) Pyrimidine Carboxamide Derivatives as Potential Fungicidal Agents

Twelve N-((2-phenyloxazol-4-yl)methyl) pyrimidine carboxamide derivatives were designed, synthesized, and characterized by 1H NMR, 13C NMR, and HRMS. The fungicidal activities of these new compounds against Sclerotinia sclerotiorum, Botrytis cinereal, and Colletotrichum fragariae were evaluated. The results indicated that compounds 5b, 5f, and 5g displayed potential fungicidal activities against tested fungi, especially 5f exhibited IC50 value of 28.9 mg/L against S. sclerotiorum. Moreover, the compounds 5f and 5g showed IC50 values of 54.8 mg/L and 62.2 mg/L against C. fragariae respectively, which shows that they were more active than the commercial fungicide hymexazol. The superficial structure-activity relationships were discussed, which may be of benefit for the development of fungicides and discovery of novel fungicides.