Seed Treatment With Systemic Fungicides: Time for Review

Pre-sowing seed treatment with systemic fungicides is a firmly entrenched practice for most agricultural crops worldwide. The treatment is intended to protect the crop against seed- and soil-borne diseases. In recent years, there is increasing evidence that fungicidal applications to manage diseases might inadvertently also affect non-target organisms, such as endophytes. Endophytes are ubiquitously present in plants and contribute to plant growth and development besides offering resistance to biotic and abiotic stresses. In seeds, endophytes may play a role in seed development, seed germination, seedling establishment and crop performance. In this paper, we review the recent literature on non-target effects of fungicidal applications on endophytic fungal community and discuss the possible consequences of indiscriminate seed treatment with systemic fungicide on seed endophytes. It is now well recognized that endophytes are ubiquitously present in all parts of the plant, including the seeds. They may be transmitted vertically from seed to seed as in many grasses and/or acquired horizontally from the soil and the environment. Though the origins and evolution of these organisms in plants are a matter of conjecture, numerous studies have shown that they symbiotically aid in plant growth and development, in nutrient acquisition as well in protecting the plants from abiotic and biotic stresses. Against this background, it is reasonable to assume that the use of systemic fungicides in seed treatment may not only affect the seed endophytes but also their attendant benefits to seedling growth and establishment. While there is evidence to indicate that fungicidal applications to manage plant diseases also affect foliar endophytes, there are only few studies that have documented the effect of seed treatment on seed-borne endophytes. Some of the convincing examples of the latter come from studies on the effect of fungicide application on rye grass seed endophyte AR37. More recently, experiments have shown that removal of seed endophytes by treatment with systemic fungicides leads to significant loss of seedling vigour and that such losses could be partially restored by enriching the seedlings with the lost endophytes. Put together, these studies reinforce the importance of seed endophytes to seedling growth and establishment and draw attention on how to trade the balance between the benefits of seed treatments and the direct and indirect costs incurred due to loss of endophytes. Among several approaches, use of reduced-risk fungicides and identifying fungicide-resistant endophytes are suggested to sustain the endophyte contribution to early seedling growth.

Etiology, Epidemiology and Management of Asian Soybean Rust (ASR) in Brazil and Vulnerability of Chemical Control of Specific without Multisite Fungicides

Brazil is the first soybean producer in the world, and the largest exporter. In the 2019/20 harvest, the country produced about 124.85 million tons, representing 30% of world production. Global soy production for 2019/20 reached 337.9 million tons. Asian soybean rust (ASR) is the most pathogen on soybean in Brazil in nowadays. Target spot and Septoria leaf spot plus white mold complete these scenarios. ASR emerged in Brazil in 1979. The use of fungicides in the soybean crop in Brazil intensified after the master of 2002 with the resurgence of soybean rust, where the use of triazoles intensified. The massive sprays to pathogen control reached 3.5 sprays per season. In 2006, the first reports of loss of sensitivity of the fungus to the group appeared, notably for the fungicide flutriafol and tebuconazole used in many situations in a curative way or to eradicate the fungus. From that moment on, the productive system sought to use triazoles and strobilurins. In 2011 came the first reports of loss of sensitivity of the fungus in the group of strobilurins. This fact was due to the use of pyraclostrobin in the vegetative phase of soybeans without protection by multisite. That same year, the introduction of the active ingredients in copper oxychloride, mancozeb and chlorothalonil took place in Brazil. In 2015, the first carboxamides ((benzovindiflupyr) (solatenol and fluxpyroxade) associated in triple mode with triazoles and strobilurins were launched on the Brazilian market. Due to the specific mode of action in the metabolism of the fungus (biosynthesis of ergosterol (triazoles), mitochondrial respiration in the cytochrome oxidase enzyme complex - QOIs (strobilurins) and succin dehydrogenase - SDHIs (carboxamides), the need for their association in the sprayings was seen. To multisite (cuprics, dithiocarbamates and nitriles). For the sustainable management of the disease in Brazil, control strategies are recommended, such as the use of systemic fungicides, with a specific biochemical mechanism of action with the adoption of tank mix with multisite, adoption of cultural practices (sanitary emptiness) and sowing schedule and the use of varieties with quantitative resistance (partial or horizontal resistance). These measures will guarantee the sustainability of the culture and the useful life of systemic fungicides or specific sites.

Fungicide management in the Asian soybean rust

Asian soybean rust is the major crop disease and the management of the use of the fungicide is important for effective control. The objective of this work was to evaluate the management of fungicides with sequential applications to control Asian soybean rust. The experimental design used was a randomized block with four replications and eight treatments with different combinations of fungicides from the following chemical groups: triazole, strobilurin, carboxamide, and dithiocarbamate. The applications were carried out with backpack spray equipment at constant pressure (CO2) and a spray rate of 200 L ha-1. The severity of rust, the area under the disease progress curve, control efficiency, mass of 1,000 grains, and productivity were evaluated. The protective fungicide mancozeb, in mixtures with systemic fungicides, were more effective for the control of Asian soybean rust than the systemic fungicides applied without the protective fungicide.

Validation of a Rapid Multiresidue Method for the Determination of Pesticide Residues in Vine Leaves. Comparison of the Results According to the Different Conservation Methods

The QuEChERS method was applied to the determination of pesticide residues in vine (Vitis vinifera) leaves by LC-MSMS. The method was validated in-house for 33 pesticides representing 17 different chemical groups, that are most commonly used in grape production. Recoveries for the pesticides tested ranged from 75 to 104%, and repeatability and reproducibility relative standard deviations (RSDr% and RSDRw%) were less than 20%. The method was applied to the analysis of pesticide residues in 17 market brands of vine leaves processed according to three different preservation methods and sampled from the Lebanese market. Dried vine leaves were more contaminated with pesticide residues than those preserved in brine or stuffed vine leaves. The systemic fungicides were the most frequently detected among all the phytosanitary compounds usually applied to grape production. Brine-preserved and stuffed vine leaves contained lower concentrations of the residues but still contained a cocktail of different pesticides.