Knowledge of droplet spectra generated by spray nozzle tips is important to ensure the quality of applications of plant protection products. However, there are different methods for this evaluation, which can cause difficulty in interpreting the results. This study aimed to evaluate the droplet spectra produced by the flat fan spray tip AD 11002 operated under different pressures and using different techniques and equipment. The volume median diameter (VMD), percentage of spray volume in droplets smaller than 100 µm diameter and relative spam (RS), considering pressures of 200, 300, and 400 kPa were determined using two direct measurement equipment (Spraytec and Shadow Sizer), based on laser diffraction and image analysis, respectively, and a measure based on indirect analysis, through the digitization of water-sensitive paper. Thus, the use of different analysis techniques led to variations of the analyzed parameters. Among the direct measurement equipment, a difference of up to 58% was observed in VMD. The use of water-sensitive paper to characterize droplet spectra must be carried out with great discretion because there is an underestimation of fine droplets. Pressure variations of 200 to 400 kPa did not influence VMD and RS.

Adjuvants are tools to maximize pesticide spray quality. This study aimed to evaluate the interaction effects between adjuvants and the fungicide azoxystrobin + benzovindiflupyr on the physicochemical characteristics, droplet evaporation time, and spray droplet size. The experiment was carried out using a 26 factorial scheme, in which the first factor was the absence or presence of the fungicide mixture (water or water + fungicide) and the second factor was the presence of different adjuvants (water and five adjuvants). The parameters evaluated were surface tension, pH, viscosity, electrical conductivity, droplet evaporation time, volume median diameter, percentage of droplets smaller than 100 µm, and relative amplitude of the droplet spectrum. The silicone and propionic acid + soy lecithin adjuvants reduced the pH of the spray solution, and the sodium lauryl ether sulfate, propionic acid + soy lecithin, and orange essential oil adjuvants reduced droplet evaporation when mixed with the fungicide. All tested adjuvants improved spray quality related to the characteristics of the droplet spectrum, reducing the percentage of droplets smaller than 100 μm, and allowing more uniform droplet size. The fungicide azoxystrobin + benzovindiflupyr affected droplet evaporation time.

Aphis gossypii Glöver is one of the main cotton insect pests, causing significant losses in the crop. In order to reduce these damages, frequent applications of insecticides are carried out, despite reported cases of resistance. One auxiliary tool of resistance management is the combination of natural and synthetic products because the combinations can deliver comparable or greater pest toxicity while reducing the necessary dose of the synthetic molecules, thus maintaining its effectiveness. Therefore, the present work evaluated the toxicity of Ocimum basilicum essential oil, the synthetic insecticide thiamethoxam and the combination of these in the control of cotton aphid. The acute toxicities of thiamethoxam and the essential oil were obtained through dose response assays; then, combinations of the two products were assessed. The essential oil had a high concentration of linalool and it exhibited toxicity to the cotton aphid. The combination of the two products caused high mortality, particularly when they were applied as the LD 50 of the thiamethoxam + LD 50 of the essential oil and the 50% LD 50 of the thiamethoxam + 50% LD 50 of the essential oil. This work concludes that O. basilicum L. essential oil combined with thiamethoxam may be an alternative in the population management of the cotton aphid and may contribute in the future to the management of resistance and reduce the environmental impact of pesticides.

The objective of this work was to evaluate injury symptoms on soybean not tolerant to dicamba (3,6-dichloro-2-methoxybenzoic acid), as well as crop yield, after the application of sub-rates of the herbicide to simulate physical drift in tropical conditions. Dicamba rates of 0, 5.8, 14.4, 28.8, 57.6, and 576 g acid equivalent per hectare were applied at the vegetative (V3) and reproductive (R1) stages of soybean, using a backpack sprayer pressurized with CO2, equipped with air-induction flat fan spray nozzles; the pressure and rate of application were 250 kPa and 200 L ha-1, respectively. Visible injury, the soil-plant analysis development (SPAD) index (leaf chlorophyll content) at 14 days after herbicide application, and soybean crop yield were evaluated. These variables were influenced by the crop stage in which the dicamba rates were applied. Rates below 28.8 g ha-1 caused less injury to soybean when applied at the R1 stage; however, there were no differences in yield between stages. A 1% dicamba drift in tropical conditions reduces soybean yield by 12%.

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