## 4 Discussion  
The presented results indicate that the increase in wetting agent rate influences the copper hydroxide deposit on the sugar beet leaves. A similar effect was observed by [12,27] in their field trials on soybeans. It is interesting to note that in field conditions, the quantity/amount of deposit was 50% lower than in laboratory experiment. This is due to weather conditions which exist in the field during the period of protection of sugar beets, which assume higher temperatures, lower air humidity, and blowing winds typical for the lowlands of the Vojvodina area where the experiment was conducted. This speculation is supported by [21], who reports that the weather conditions affect the efficacy of pesticide application. During the field experiment, there was no precipitations, but we speculated that the trend of fluctuation of the deposit value after the rain would coincide with the laboratory-simulated trend of a decrease caused by the mentioned weather conditions. The coefficient of variation (CV) of a transverse distribution depends on the application of the wetting agent. For laboratory conditions, the CV of the transverse spray distribution measured on the paternator should be lower than 10% and ideally lower than 7%. Only such a distribution guarantees the good quality and efficiency of protection on the whole working surface of the sprayer booms [28]. It is interesting to analyze the behavior of the coefficient of variation (CV) of the transverse distribution of nozzles with the increase in the rate of pinole-based wetting agent. At a rate of 1 L ha\({}^{-1}\) CV increases from 43.73% to 62.81%. With rates of 0.3 and 0.6 L ha\({}^{-1}\), the CV value is not high but is unacceptable because it ranges from 10.64% to 33.93% for TD ADF nozzles and 17.91 to 24.51% for SF nozzles. It is a totally different situation than in laboratory experiment where CV decreases with the addition of a wetting agent. Using a wetting agent, the hydraulic characteristics of the working liquid change and, therefore, the behavior of the drops during disintegration in nozzles changes too [29,30]. This, in combination with field conditions and working parameters, is the probable reason for the high coefficient of variation in the field treatment when applying pinole-based \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type of Nozzle** & **Treatment I** & **Treatment II** & **Treatment III** & **Treatment IV** \\ \hline SF & 31.50  
\end{table} 
Table 2: Tracer recovery rate solutions on sugar beet leaves using SF and TD ADF nozzles in tests under field conditions. wetting agent at a rate of 1 L ha\({}^{-1}\). The solution for the optimal coefficient of variation needs to be searched for in a good combination of the nozzle type, working parameters of a treatment, and wetting agent rate. In this work, the mentioned solution was achieved when wetting agent was applied at a rate of 0.6 L ha\({}^{-1}\) using TD ADF nozzles. Even though the results suggested that increasing the rates of wetting agent increases cooper hydroxide deposits on sugar beet leaves, there is a question of an allowed increase in the wetting agent concentration. According to available information, the maximum allowed dosage of a pinole-based wetting agent, depending on the region, is 1.5 L ha\({}^{-1}\) (source: Miller solutions), while in the Republic of Serbia it is registered at a dosage of 0.3 L ha\({}^{-1}\). The obtained results open new research possibilities for the determination of antifungal effects on the CSL causal agent under these conditions. Moreover, there is a possibility to reassess and reestablish the lowest amount of a wetting agent sufficient for providing satisfactory efficacy of copper hydroxide for protection of sugar beet against CLS causal agent. Satellite images can be used for early detection of CLS in sugar beet [28]. Based on the obtained values and the analysis of the TGI vegetation index, the beginning of the infection with CLS on the sugar beet leaves was determined.