ABSTRACT Droplet spectrum quality is essential to effectively control crop pests and diseases. This study aimed to characterize the droplet uniformity of the eight most popular flat-fan nozzles used by Brazilian farmers and relate it to their spraying quality. The method consisted of using a laser-diffraction-size analyser to determine droplet-size distribution for three fungicide spray solution compositions and at two flow rates. Our goal was to identify the nozzle models with the highest and lowest Span values for each fungicide spray solution. In the first stage, the results confirmed differences in uniformity and droplet size for both nozzle models and flow rates applied. However, these differences were not the same for both flow rates nor constant for all fungicide spray solution compositions. Through field experiments, we could understand how the combination of flow rate, nozzle model, and spray solution composition provides different results and application efficiencies. Based on our results, we can state that Span has an impact on the number of droplets prone to drift and quality of canopy coverage. Therefore, this droplet-quality parameter should be considered and displayed in nozzle catalogues to improve nozzle selection and sprayer configuration, thus enhancing application quality.

ABSTRACT The herbicide glyphosate is sprayed with varying application volumes that result in different concentrations used in the spray solutions. Thus, this study aimed to evaluate the effect of glyphosate concentrations on the potential risk of droplet drift, surface tension of spray solution, and contact angle of droplets on surfaces. Three experiments were conducted in a completely randomized design. Drift potential was evaluated by median volumetric diameter (MVD), percentage volume of droplets with diameter smaller than 100 μm (%V<100 μm), and coefficient of uniformity (Span), with 12 replications. The surface tension of spray solutions and contact angle of droplets were evaluated on Urochloa ruziziensis leaves, paraffin film, and glass, with four replications. Changing glyphosate concentrations in the spray solution changes the droplet spectrum and contact angle on different surfaces due to changes in spray solution physicochemical characteristics, such as surface tension. The increased glyphosate concentrations in the spray solution lead to increased drift potential of droplets, reducing the surface tension and contact angle of droplets on surfaces.

RESUMO O uso de adjuvantes associados a herbicidas visa melhorar o desempenho da aplicação e o consequente aumento do efeito biológico do tratamento. Porém, a ordem de adição dos produtos ao tanque do pulverizador pode trazer importantes influências à calda fitossanitária. Assim, o objetivo desta pesquisa foi avaliar o controle de Senna obtusifolia em função da sequência de adição do herbicida aminopiralide + fluroxipir e de adjuvantes no preparo das caldas. Foram utilizadas duas dosagens de herbicida (1 e 2 L p.c. ha-1), associadas aos adjuvantes óleo mineral (OM); copolímero de poliéter e silicone (SIL); mistura de fosfatidicolina e ácido propiônico (LEC), todos na proporção de 0,3% v v-1, com adição alternada à calda para avaliar os efeitos da sequência de preparo. O volume de calda considerado foi de 150 L ha-1. Foram realizadas avaliações da estabilidade da calda a partir da avaliação visual de homogeneidade, condutividade elétrica e pH. O efeito do tratamento no controle de S. obtusifolia foi mensurado por meio de uma escala de pontuação e pela massa seca. Também foram determinados os coeficientes de correlação entre as avaliações. Verificou-se que não houve diferença da sequência de preparo da calda para a estabilidade, o pH e a condutividade elétrica. Porém, a sequência de preparo influenciou o controle inicial de S. obtusifolia, sem efeito sobre a massa seca. O tratamento com o adjuvante LEC adicionado ao herbicida proporcionou maior taxa de controle na maior dosagem, enquanto o adjuvante de SIL teve o efeito oposto.

ABSTRACT The use of adjuvants associated with herbicides aims at improving the performance of application and the consequent increase in the biological effect of the treatment. However, the sequence of product added to the sprayer tank can influence the phytosanitary spray solution. Thus, this study aimed to evaluate the control of Senna obtusifolia as a function of the sequence of addition of the herbicide aminopyralid + fluroxypyr and adjuvants in the preparation of spray solution. Two herbicide doses (1 and 2 L c.p. ha-1) associated with the adjuvants mineral oil (MO), silicone polyether copolymer (SIL), and a mixture of phosphatidylcholine and propionic acid (LEC), all in the proportion of 0.3% v v-1, with alternate addition to the spray solution to evaluate the effects of the preparation sequence. The spray solution volume considered was 150 L ha-1. Evaluations of spray solution stability were performed from the visual evaluation of homogeneity, electrical conductivity, and pH. The effect of treatment on S. obtusifolia control was measured using a scoring scale and dry matter. Correlation coefficients between the evaluations were also determined. No difference of the preparation sequence of spray solution was observed for stability, pH, and electrical conductivity, but an influence was observed on S. obtusifolia control, without changing dry matter accumulation. The treatment with the adjuvant LEC previously added to the herbicide provided a higher control rate at the highest dose, while the adjuvant SIL had the opposite effect.

ABSTRACT The high susceptibility to diseases of fine table grapes cultivars demand intensive use of pesticides, and the presence of water on the leaf surface can worsen the deposition of these products. The objective of this study was to evaluate the spray deposition in vine leaves in different conditions of leaf wetness, and test the effectiveness of an artificial ventilation method to remove water on the leaf surface. We evaluated the spray deposition in vine applied over: wet canopy (presence of high leaf wetness); canopy dried artificially (dried with air jet from air-assisted sprayer, wind speed of 25 km h−1) and canopy dried naturally (naturally dried leaves and free of water on its surface). Saline marker was used in the spray and the deposition on the canopy was determined by conductimetry. A pesticide application in vine, with the presence of water in the leaf surface, causes losses by run-off and reduces the deposit of spraying. The use of air jet formed by air-assisted sprayer fan is efficient for the removal of water on the vine leaf surface and its use can increase the favorable period for the application of pesticides without causing dilution and losses by run-off of the applied product.