In agriculture, the mixing of pesticides in tanks is a common practice. However, it is necessary to previse possible physical-chemical implications of this practice, which may affect the efficiency of the treatments performed. Therefore, the objective of this study was to evaluate the effects of the addition of acaricide to insecticidal spray mixtures on the formation of spray droplets and the interaction with citrus leaves. The experimental design was totally randomized, in a (2 × 3 + 1) factorial scheme for seven treatments. Factor A corresponded to the spray mixture used (isolate or in the mixture). Factor B corresponded to the insecticides tested (lambda-cyhalothrin + thiamethoxam, phosmet, and imidacloprid) and the control consisted of a spray mixture with spirodiclofen only. Nine replications were performed for characterization of the spray droplet size spectrum and four replications for the analysis of the surface tension and the contact angle. The mixture of pesticides showed positive results in terms of application safety. The addition of acaricide to insecticide spray mixtures reduced the surface tension and contact angle of droplets on the adaxial surface of orange leaves. There was an increment in volume median diameter (VMD), a significant reduction in the volume of droplets with drift-sensitive size and improvement in the uniformity of droplet size. Therefore, the addition of acaricide to an insecticide spray mixture positively influenced spray droplet formation and the interaction with citrus leaves providing better coverage and droplet size fractions with an appropriate size for safe and efficient application.
Significant differences in the physical and mechanical properties exist between the rock masses on two sides of an ore-rock contact zone, which the production tunnels of an underground mine must pass through. Compared with a single rock mass, the mechanical behavior of the contact zone composite rock comprising two types of rock is more complex. In order to predict the overall strength of the composite rock with different contact angles, iron ore-marble composite rock sample uniaxial compression tests were conducted. The results showed that composite rock samples with different contact angles failed in two different modes under compression. The strengths of the composite rock samples were lower than those of both the pure iron ore samples and pure marble samples, and were also related to the contact angle. According to the stress-strain relationship of the contact surface in the composite rock sample, there were constraint stresses on the contact surface between the two types of rock medium in the composite rock samples. This stress state could reveal the effect of the constraint stress in the composite rock samples with different contact angles on their strengths. Based on the Mohr-Coulomb criterion, a strength model of the composite rock considering the constraint stress on the contact surface was constructed, which could provide a theoretical basis for stability researches and designs of contact zone tunnels.