Biologized control of the main diseases of cherry plum in humid subtropics of the Krasnodar region

Chemical fungicides are usually used to combat phytopathogens in stone fruit crops, in particular cherry plum ( Prunus cerasifera Ehrh.). Biofungicides are an alternative to chemicals. Biofungicides preparations are based on saprotrophic bacteria and fungi. Most of these drugs suppress the reproduction of fungal plant pathogens thus reducing the infectious load. These drugs induce immune responses in plants, increasing their resistance to pathogens and unfavorable environmental factors. In this work, for the first time in humid subtropics, we have given a comparative assessment of the biological effectiveness of the biofungicides Baktofit, Vitaplan, Gamair, Fitosporin-M, used together with the chemical fungicides Skor and Horus at half the rate of application. Our goal was to develop systems of biologic protection of cherry plum from the main diseases (clusterosporium disease, moniliosis, and gray rot of fruits) based on biological products in combination with reduced doses of chemical fungicides in conditions humid subtropics of the Krasnodar Territory. The work also aimed to assess the effect of such systems on the yield and annual growth of axial shoots of cherry plum. The research was carried out in 2015-2017 in plantings of cherry plum variety Obilnaya at the production sites of the State Unitary Enterprise of the Krasnodar Territory “Oktyabrsky” (Sochi). We compared the effect of various Bacillus subtilis bacteria-based fungicides, namely Baktofit, SP (Sibbiopharm, Russia), Vitaplan (AgroBioTechnology, Russia), SP, Gamair, SP (AgroBioTechnology, Russia), and Fitosporin-M, Zh (BashInkom, Russia) in mixes with half the norms of Horus (Horus®, Syngenta AG, Switzerland) and Skor (Skor®, Syngenta AG, Switzerland), as well as the Trichoderma harzianum -based preparation Glyokladin, Zh (Agrobiotekhnologiya, Russia) without mixing with Horus and Skor. Trees were sprayed with fungicide solutions twice during the spring season, in the bud-swelling phase and in the phase of active shoot growth after flowering. The water was control during the treatment. The chemical fungicides Horus (1st treatment) and Skor (2nd treatment) were as a reference. The intensity of the development of clusterosporiosis, monilioz and gray rot of fruits and the biological effectiveness of the preparations used, the yield and the value of the annual growth of axial shoots were assessed. According to a three-year experiment, the bacterial biofungicide Fitosporin-M in combination with half the consumption rates of Horus and Skor and the fungal biofungicide Glyocladin without chemical fungicides showed the maximum statistically significant biological effectiveness in protecting cherry plum from clusterosporia, gray rot and brown monilial rot. The efficiency of Gamair turned out to be slightly lower, but it still exceeded the indicators of the reference treatment with chemical fungicides. The efficiency of Baktofit in most cases was lower than the reference. Vitaplan showed the lowest efficiency in all variants. The biological effectiveness of all tested preparations against monilial brown rot was lower than in the case of gray rot and clusterosporiosis. The yield of cherry plum when treated with Fitosporin-M, Glyokladin and Gamair was practically the same in all tests (9.8-11.5 t/ha), being approximately 1.8-1.9 times higher than the control values (5.4-5.7 t/ha) and 1.1-1.2 times higher than the reference (8.9-9.1 t/ha). When using Baktofit, the yield of cherry plum was almost equal to the reference (8.7-9.4 t/ha), while when treated with Vitaplan it was regularly below the reference (6-7 t/ha). The preserved yield upon treatment with biological preparations reached 9.7-11.5 t/ha. The increase in the growth of the axial shoots of cherry plum compared to the control turned out to be maximum (1.7 times) for Glyokladin and slightly less for Fitosporin-M and Gamair, while when using Baktofit and Vitaplan it was 15-25 % lower than the reference values and only 1.1-1.2 times higher than the control values. Thus, biological plant protection products based on Bacillus subtilis and T richoderma harzianum can be successful against the main diseases of cherry plum in the subtropics of Krasnodar Territory. It is acceptable to use bacterial preparations in a mixture with lower rates of chemical fungicides. This approach is more environmentally friendly and reduces the cost of plant protection.