Introduction
The use of novel nozzles and natural gums has gained significant attention for improving the physical properties of spray solutions and reducing drift during herbicide application. It is essential to optimize spray droplet stability and deposition to enhance herbicide effectiveness while minimizing environmental risks. Despite advancements in spray technology, the potential impact of various plant-derived gums on droplet behavior remains unclear. This study aims to evaluate the effects of different plant gums on the activity of clodinafop-propargyl and the physical characteristics of spray droplets in the control of winter wild oat.
Materials and Methods
This study was designed as a dose-response experiment to investigate the effects of adding 12 different types of plant gums—namely pectin, Carboxymethyl cellulose(CMC), guar, konjac, dextran, xanthan, carrageenan, sodium alginate, Farsi, gum tragacanth, gum Arabic, and gellan—to a spray solution of the herbicide clodinafop-propargyl. The herbicide was sprayed using three types of flat fan nozzles: standard, anti-drift, and air-induction. The research focused on the spray coverage and effectiveness in controlling winter wild oats under greenhouse conditions. Additionally, the study examined how these gums influenced various factors, including the viscosity of the spray solution, the contact angle, the spread area, and the evaporation rate of herbicide droplets placed on the upper and lower surfaces of winter wild oats leaves.
Results and Discussion
The results indicated that konjac, CMC, and gellan gums produced the highest viscosity in the clodinafop-propargyl spray solution, with viscosities of 89.8, 93.9, and 195.4 mPas/s, respectively. However, these gums did not affect the efficacy of the herbicide against winter wild oats. Xanthan, guar, and CMC gums achieved the highest droplet-leaf contact angles (greater than 55°), with xanthan gum resulting in the longest droplet evaporation time of approximately 30 minutes. In contrast, gellan and konjac gums led to the shortest droplet evaporation times, which were less than 10 min. Among sprays with a standard flat fan nozzle, the addition of guar, xanthan, and sodium alginate gums increased spray coverage. Among sprays with an anti-drift flat fan nozzle, the addition of guar, konjac, sodium alginate, and Persian gums improved spray coverage. Among sprays with an air-induction flat fan nozzle, the addition of cellulose, guar, konjac, xanthan, and Persian gums increased spray coverage. In sprays with standard, anti-drift and air-induction flat fan nozzles, the ED50 value in the control treatment without gum was 15.8, 20.5 and 16.9 g a.i. ha-1, respectively.
Among the sprays with the standard flat fan nozzle, except for the addition of gum arabic, the addition of gums to the spray solution had no effect on the ED50 and ED90 values. Among the sprays with the anti-drift flat fan nozzle, the addition of pectin, cellulose, guar, konjac, dextran, xanthane, and sodium alginate gums caused a decrease in the ED50 value, and the addition of pectin, cellulose, guar, konjac, dextran, xanthane, and guar gums caused a decrease in the ED90 value. Among the sprays with the air-induction flat fan nozzle, the addition of guar and sodium alginate gums caused a decrease in the ED50 value, and the addition of guar gum caused a decrease in the ED90 value. These results indicate that in the sprays with the anti-drift flat fan nozzle, there is a greater need for the presence of gums in the solution, and out of 12 types of gums used, 8 types of gums improved the herbicide efficiency. Additionally, adding guar gum to the spray solution applied with an air-induction flat fan nozzle resulted in the highest spray coverage of 39.3% on moisture-sensitive paper. This combination also required the lowest herbicide dose to control 50% and 90% of the dry weight of winter wild oats (11/89 and 33/69 g a.i. ha-1, respectively). Based on these findings, this treatment is recommended as the most effective option.
Conclusions
Overall, there is a significant need to incorporate gum into the spray solution when spraying it with anti-drift falt fan nozzle. Based on the findings of this study, the recommended approach is to use a clodinafop-propargyl spray solution that includes guar gum in conjunction with an air-induction flat fan nozzle. In contrast, adding gellan and xanthan gums to the clodinafop-propargyl spray solution did not enhance its effectiveness against winter wild oats. However, these gums can increase the viscosity of the spray solution and prolong the evaporation time of the spray droplets, making them potentially beneficial in windy, hot, and dry environments.