Evaluation of the growth regulator Stimmunol EF<sup>®</sup> influence on resistance of peach tree to the main phytopatogenes and on productivity of culture

Abstract

The subtropical zone of the Black Sea coast of Russia is favorable for peach growing, but the crop is susceptible to a number of diseases that adversely affect the productivity and quality of fruits. The main method of peach protection is chemical, however, the long-term use of fungicides entails a serious environmental burden on the agrocenosis as a whole and leads to the emergence of resistance of phytopathogens. Thus, the study of the effectiveness of the drugs use that increase the natural plants immunity is an extremely relevant scientific area. In a field experiment, the influence of the growth regulator Stimmunol EF® in different application rates on the peach resistance to the main diseases of fruits and leaves, as well as crop yield, was investigated. The studies were carried out in peach orchards (Red Haven cultivar) of the Federal Research Centre the Subtropical Scientific Centre of the Russian Academy of Sciences (Russia, Sochi) according to standard methods in 2021-2022. The assessment of the Stimmunol EF® immunostimulating effect on peach in relation to leaf curl was carried out against an average infectious background (development of the disease in control 31.2 % in 2021 and 33.4 % in 2022). Standard treatment (Delan®; Skor®) reduced the intensity of leaf curl development by 4 and 5.7 times, in the first and second years of the experiment, respectively. Stimmunol EF® restrained the development of the disease at the level of the standard. The biological effectiveness of Stimmunol EF® against leaf curl reached 70.3-72.4 % at the peak of the maximum development of the disease (in May). The intensity of clusterosporiosis development was at a high level and reached 37.5-49.8 % in July. The use of fungicides in the standard restrained the development of the disease by 4.2 times. With the use of Stimmunol EF® (100 ml/ha), the development of the disease decreased by 3.8 times in 2021 and 2.9 times in 2022. Biological efficiency was 74.2 % and 66.4 % at the maximum rate of application of the drug (100 ml/ha); 67.8% and 48.5% – at the minimum (50 ml/ha), respectively, in the first and second years of research. The biological efficiency of the standard was 76.7-75.2 %. The intensity of fruit rot development in the control ranged from 13.6-17.1 %, in the standard it did not exceed 6.1 %. Stimmunol EF® inhibited the fruit rot development only at the maximum application rate of 100 ml/ha (maximum biological efficiency was 58.4 %). The yield of peach when treated with growth regulator Stimmunol EF® increased by 132.8-176.2% relative to the control.