Extended Abstract
Introduction
Currently, herbicides are considered an essential tool to control weeds in agro-systems, and a large part of the increase in crop yields depends on them. One of the pillars of the rational use of herbicides is the selection of appropriate application equipment. Nozzle technology has always been advancing so that one of its products is dual flat fan nozzles, creating two non-vertical injections, with an angle between the flat fans. They may have symmetrical or asymmetrical injection geometry. In General, dual flat fan nozzles have been showed better performance compared with single flat fan nozzles on herbicide efficacy. Spray angle correction, or in other words, angling the spray path of the fan, significantly improves spray coverage on weeds and has therefore been proposed as a simple and inexpensive solution for optimizing herbicide use. However, despite the availability of dual flat fan nozzles, no study has been conducted to date on the effect of changing the spray direction of the fans in dual flat fan nozzles on spray coverage and herbicide efficacy. In this study, it was hypothesized that changing the spray direction of the fans in dual flat fan nozzles could affect the efficacy of imazethapyr herbicides against velvetleaf. Therefore, this study was conducted with the aim of accepting or rejecting the above hypothesis and also the influenceability of the above hypothesis on the size of the spray droplets.

Materials and Methods
The experiment was conducted during the summer of 2024 at Bu-Ali Sina University, Hamedan, Iran. It was conducted as a factorial completely randomized design with three replications. The first factor was the herbicide dose, including six doses of imazethapyr (0, 6.25, 12.5, 25, 50 and 100 g a.i. ha-1), the second factor was the nozzle type, including three types of flat fan nozzles (standard, anti-drift, and air-induction), and the third factor was the injection geometry of nozzle, using 1 single flat fan nozzle and 7 dual flat fans nozzles. Treatments were applied at the seven-leaf stage of velvetleaf between 6-8 am. Immediately after spraying, the spray coverage on water-sensitive papers installed at three different positions was measured. Moreover, chlorophyll fluorescence and dry weight were measured 3 and 28 days after spraying, respectively.

Results and Discussion
In two of the three water-sensitive paper positions, the spray coverage ranking with single flat fan nozzles was standard > anti-drift > air-induction. These results indicate greater spray coverage with smaller spray droplets, resulting in a greater reduction in the area between the Kautsky curve and the maximum chlorophyll fluorescence. However, the ED50 values with single flat fan nozzles were ranked as standard < air-induction < anti-drift, with 14.46, 15.03, and 19.84 g imazethapyr ha-1, respectively. In addition, the results showed that the number of fans had a positive effect on the efficacy of imazathapyr against velvetleaf, but its effectiveness decreased with increasing droplet size. Although the droplets produced with the air-induction nozzles were larger and produced less spray coverage, they were able to settle and possibly penetrate more effectively due to the presence of air bubbles, resulting in better herbicide efficacy. The number of fans also affects the efficacy of imazathapyr against velvetleaf, with droplet size inversely related to the number of fans. As the size of the spray droplets increases, the effectiveness of being two fans decreases. Also, the angle setting of the dual flat fan nozzles was found to be a determining factor in the efficacy of imazathapyr against velvetleaf. Among the standard dual flat fan nozzles, the lowest and highest ED50 values were observed with one fan spraying 5° backward and another fan spraying 35° backward (10.87 g imazathapyr ha-1) and with one fan spraying 45° forward and another fan spraying 15° forward (14.74 g imazathapyr ha-1), respectively. Among the anti-drift dual flat fan nozzles, the lowest and highest ED50 values were observed with one fan spraying 5° forward and another fan spraying 25° backward (10.82 g imazathapyr ha-1) and one fan spraying 45° forward and another fan spraying 15° forward (26.09 g imazathapyr ha-1), respectively. Among the air-induction dual flat fan nozzles, the lowest and highest ED50 values were observed with one fan spraying 25° forward and another fan spraying 5° backward F25B5 (11.45 g imazathapyr ha-1) and one fan spraying 45° forward and another fan spraying 15° forward (16.57 g imazathapyr ha-1), respectively.

Conclusion
Based on the results of the present study, one of the following three treatments is recommended for spraying imazathapyr against cotton bollworm: 1) standard dual flat fan nozzle with one fan spraying 5° backward and another fan spraying 35° backward, 2) anti-drift dual flat fan nozzle with one fan spraying 5° forward and another fan spraying 25° backward, and 3) air-induction dual flat fan nozzle with one fan spraying 25° forward and another fan spraying 5° backward.