Theoretical foundations and methods of biological plant protection

The preparation Pentaphag is effective against angular leaf spot of cucumber, bacterial canker of pome fruits, shot-hole disease of stone fruits, and bacterial spots of tomatoes. However, in 2001, it was excluded from the List of pesticides and agrochemicals due to a lack of demand.

Another method for controlling viral infections is pre-inoculation — vaccinating plants with weakly pathogenic strains of viruses. This practice allows for the prevention of severe epiphytotics on plantations. To protect tomato cultivars susceptible to tobacco mosaic virus (TMV) in open and protected ground, the vaccine strain TMV-U-69 is used. It is a stable natural strain that provides a long-lasting protective effect without the plants exhibiting symptoms of the disease.

• Commercial biological preparations worldwide — more than 40
• Bacteriophage yield from one cell — 100–200 units
• Stability of vaccine strain TMV-U-69 — 99.7%

Vaccination of vegetable crops against viral diseases

Vaccination with weakened strains protects greenhouse vegetables from severe courses of viral infections. The preparation suppresses the development of the disease without the manifestation of external symptoms and reduces the concentration of aggressive viral particles. Before the mass introduction of resistant hybrids of tomatoes, this method was used on an industrial scale, with at least 100 hectares of greenhouses treated annually.

To protect tomatoes, the vaccine strain U-69 is used, which provides an average yield increase of 23%. Treatment is carried out once by spraying the seedlings with an aqueous solution of the preparation. The technology requires strict adherence to timelines and temperature regimes.

1. Prepare an aqueous solution of the vaccine strain U-69 and add carborundum No. 20 to it at 15 g/L for better vaccine penetration.
2. Spray 8–10-day-old seedlings at the stage of unfolded cotyledon leaves or the rudiments of true leaves.
3. Complete the treatment no later than 3–4 days before transplanting the seedlings.

A similar technology is used to protect cucumber in protected ground against cucumber green mottle mosaic virus (CGMMV). Without protection, this disease, which spreads through seed and during cultivation, accounts for 20 to 45% of harvest losses. Vaccination with the preparation VIROG-43, based on a stable weakly pathogenic strain (genetic stability 98%), helps minimize these losses.

10–12 days after the treatment, a very mild mosaic may appear on the cucumber plants, which later disappears completely. The concentration of the pathogen in the tissues decreases by 2–5 times compared to non-vaccinated plants. More than 80% of the plantings remain asymptomatic until the end of the growing season.

Bacterial biological products based on pseudomonads

The basis of modern bacterial products against plant diseases is made up of bacteria of the genera Pseudomonas and Bacillus. Saprotrophic pseudomonads (Pseudomonas fluorescens, P. putida, P. aureofaciens) colonize the rhizosphere and serve as natural regulators of soil-borne phytopathogens. They grow rapidly, assimilate organic matter, and actively produce antibiotics, bacteriocins, siderophores, and growth stimulants.

Among the antibiotics secreted by pseudomonads, the most important are phenazine-1-carboxylic acid, 2,4-diacetylphloroglucinol, and pyrrolnitrin. Based on pyrrolnitrin, first isolated in 1964 from P. pyrrocinia, well-known chemical fungicides were created — fludioxonil (Maxim group products) and fenpiclonil (Beret group products). Today, the synthesis genes for these antibiotics have been cloned, which opens the way for creating even more effective bioagents.

An important role is played by the ability of pseudomonads to produce siderophores — compounds that carry out the transport of iron. Under deficiency conditions, they firmly bind trivalent iron, depriving soil pathogens of nutrition. For example, the germination of chlamydospores of the Fusarium wilt pathogen Fusarium oxysporum is completely stopped at an iron concentration in the soil of 10-7–10-77 M.

To increase the effectiveness of the products, scientists use methods of genetic modification. Thus, the introduction of a plasmid into P. putida cells allowed the bacteria to use salicylate as a food source. This increases the population of beneficial bacteria in the root zone of plants. Domestic products such as Planriz (formerly known as Rizoplan), Pseudobacterin-2, and Agat-25 have been created based on pseudomonads.

• Increase in tomato yield from vaccination — 23% on average
• Carborundum No. 20 consumption — 15 g/l
• Stability of the strain in the VIROG-43 vaccine — 98%
• Titer of the Planriz product — 2 x 10⁹ cells per 1 ml

The Planriz product is produced in the form of a culture liquid based on the AP-33 strain of Pseudomonas fluorescens bacteria. It is produced at biological factories to protect cabbage plantings. Bacteria are applied to the seed, colonize the rhizosphere of the young plant, and create a protective barrier through the release of antibiotics, siderophores, and growth-stimulating substances.

When treating the leaf surface of vegetation-stage plants, the bacteria attack the leaf epithelial cells and trigger a non-specific response of the plants, which is expressed in the release of phytoalexins (substances that cause a general increase in plant immunity). This feature served as a justification for attempts to use Planriz as a preventive agent in the fight against diseases such as tomato and potato late blight, downy mildew, and cucumber powdery mildew.

Application. Double treatment is recommended during the growing season upon the appearance of the first signs of the disease. A repeat treatment in 20 days. The product is non-toxic and has a short pre-harvest interval (two days). Planriz can be used in tank mixtures with insecticides: Rovicurt, Actellic, Ambush, Cymbush, and Decis (Dzhalilov, Korsak, Perebityuk, 1994).

In domestic literature, there are numerous reports on the high effectiveness of Planriz against Fusarium wilt, powdery mildew, root and basal rots, and late blight on vegetable, fruit, berry, and many other crops. However, the product is not yet registered for these crops. For example, treating cucumber plants against bacteriosis at a rate of 1 l/ha suppressed the development of the disease compared to the control by 30%. The product produced by the Liskinskaya biological factory (titer 5 billion spores/ml) has proven itself well. It was used for seed treatment on the day of sowing at a rate of 20 ml/kg of seed. This significantly reduces plant infection with blackleg and vascular bacteriosis. Upon detection of the first signs of bacteriosis, plants are treated with a 0.1% working solution of the product at a rate of 0.3 l/ha. Repeat treatment — in 20 days. When using this product on tomatoes at a rate of 0.5-1 l/ha, a high biological effectiveness of 94.7-95.4% was obtained. To treat the surface of vegetation-stage plants, the product is diluted 500-1000 times (from 2 to 6 l per ha). The application technology is similar to the use of contact products with the use of stickers (adjuvants). Treatment of plants before the manifestation of the disease is recommended. If necessary, repeated spraying is possible, especially under unfavorable weather conditions 2 EE | o vascular -H on the day of sowing 0.3 bacteriosis Spraying during the growing season with a 0.1% working solution at -(2) 10 ml/ 10 l of water (L) vascular and mucous - (2) 10 ml/10 l of water bacterioses upon the appearance of the first signs of the disease. Repeat treatment in 20 days Pseudobacterin-2. L and Pseudobacterin-2. PS

Active ingredient. Strain B-1393 of the bacterium Pseudomonas aureofaciens.

Formulation. Culture liquid with a titer of 2-3 x 10^9 cells per ml and a powder preparation with a titer of 2-3 x 10^10 cells per ml developed at the Institute of Biochemistry and Physiology of Microorganisms of the Russian Academy of Sciences (Pushchino, Moscow Region).

Product characteristics. Biological plant protection product">plant protection product against fungal and bacterial diseases based on live cells of bacteria of the genus Pseudomonas, possessing growth-stimulating effects on plants. The biological product was developed at the G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms of the Russian Academy of Sciences.

Mechanism of action. The protective effect is based on the ability of this pseudomonad strain to synthesize phenazine-series antibiotics, which effectively suppress the growth of many phytopathogenic fungi.

Application. When used on vegetable crops, the working solution for seed treatment must contain at least 200 thousand active cells, and for the irrigation of plants during the growing season and treatment of transplant roots — 20 thousand active cells (10% and 10^7 per ml, respectively).

TABLE 17. RECOMMENDATIONS FOR THE USE OF PSEUDOBACTERIN-2 SERIES PRODUCTS List of PESTICIDES and AGROCHEMICALS..., 2001 Product name Crop Target Application rate Method, timing of treatment, application specifics (frequency) Pre-harvest interval (days) Gelmintosp 9% (P. aureofaciens), L | Seed soaking for 18-24 hours before sowing. Rate — 1.0-1.5 l/kg - (-) Cucumber Root rots Brown SPOT Spraying during the growing season with an interval of 20 days - (2) Pseudo-bacterin-2, L | Gelmintosp (P. aureofaciens), L | Seed soaking for 18-24 hours before sowing. Rate — 1.0-1.5 l/kg - (-) Tomato Root rots Brown SPOT Spraying during the growing season with an interval of 20 days - (2) Fusarium, Rhizoctonia, Pythium root rots Brown SPOT | Seed soaking for 18-24 hours before sowing. Rate — 1.0-1.5 l/kg | Spraying during the growing season with an interval of 20 days. Rate — 1000 l/ha - (2) Pseudo-bacterin-2, P | Fusarium, Rhizoctonia, Pythium root rots Olive SPOT | Seed soaking for 18-24 hours before sowing. Rate — 1.0-1.5 l/kg | Tomato | Spraying during the growing season with an interval of 20 days. Rate — 1000 l/ha - (2)

Pseudobacterin-2 is recommended for the pre-sowing treatment of cucumber and tomato seeds against root rots and for spraying the same crops against olive spot.

Efficiency and advantages of the product. The yield increase of tomato and cucumber in a greenhouse averages 15-20%. The product does not have a negative impact on the quality of the produce and is harmless to humans and warm-blooded animals. Pseudobacterin-2 is compatible with chitosan, unlike similar products (Agat-25, Planriz). The use of Pseudobacterin-2 together with chitosan, in addition to increasing the biological effectiveness of the products, extends their duration of action. To expand the spectrum of protective and stimulating action, Pseudobacterin-2 can be used in multi-component mixtures with other biological products, for example, pseudomonad strains or fungal preparations based on Trichodermin.

Shelf life of the product is 45 days at a temperature of 4-5°.

Products based on Bacillus genus bacteria

Among aerobic spore-forming bacteria, Bacillus subtilis is of the greatest importance as a biological agent for suppressing the number of phytopathogens. Reports also mention the possibility of using Bacillus mycoides and Bacillus cereus for plant protection against diseases.

Bacillus subtilis is known as hay bacillus and is widespread in soil, water, and air. B. subtilis forms convex, rhizoid-shaped colonies. It grows well on MPA, peptone-corn agar, and other media. Cell size is 0.7-0.8 x 2-3 µm. In the soil, bacilli exist either in a spore state or as vegetative cells. B. subtilis is a producer of more than 70 antibiotics. Some of them suppress the growth of phytopathogenic microorganisms.

Bactofit, SP Active ingredient. Live culture of the Bacillus subtilis IPM 215 strain and the antibiotic it produces from the aminoglycoside group. Mechanism of action. During production, an antibiotic is formed in the culture liquid capable of inhibiting the development of phytopathogens of various origins: bacteria and fungi. This same antibiotic is released by the bacteria in the soil, which provides a protective effect against soil-borne phytopathogens. For example, in a Petri dish on an agar medium, one can see the interaction of Bacillus subtilis and Fusarium sp., between which a sterile zone forms where the pathogen mycelium does not penetrate. Formulation. Wettable powder with biological activity (BA) 10000 EA/g. Developed at the State Research Center for Applied Microbiology (Protvino, Moscow Region) with the initial name — Bacifit. Available as a wettable powder of grayish or light brown color with a faint odor. It contains a sticker and a stabilizer, is low-toxic to animals, and does not have a negative effect on plants. The product is hygroscopic, so it must be stored in a tightly closed container. Guaranteed shelf life is two years at temperatures from +30 to -30°.

Application. Soaking tomato seed and irrigation of seedlings before and after transplanting (10 ml/1 l of water) reduces plant infection with blackleg by 96%, and root rot by 91%. Recommendations for application are provided in Table 18.