Growing lettuce and other greens (basil, cilantro, mint, etc.) in greenhouses has become widespread due to constant demand. So-called "lettuce lines" have been developed for this purpose. A technological feature of growing lettuce and other greens is their short growing season (no more than 30-40 days), while the total growing period can be 10-11 months, meaning 9-12 growing cycles can occur during the entire growing season. Therefore, seeding is carried out in stages at short intervals. All hydroponic lettuce cultivation technologies: firstly, plants of different sowing dates are grown simultaneously in the same array, and secondly, the same solution is circulated to nourish the plants. Thus, lettuce lines are a widely used interplanting method for growing plants. Interplanting presents challenges in protecting plants from pests and diseases. Firstly, we cannot use pesticides on green crops during the growing season. Secondly, there is constant contact between diseased and damaged plants and healthy ones. Thirdly, we perform a complete disinfection of lettuce lines once a year, usually during the summer months, when demand for produce drops.

At the beginning of cultivation, we have virtually sterile conditions. The limited protective measures available during the growing season require special attention to the entry routes of pathogens and pests into lettuce systems. Pests primarily enter from the greenhouse area or from adjacent greenhouses. These include aphids (Fig. 1), thrips (Fig. 2), spider mites, and greenhouse whiteflies. Pests can also survive on weeds growing in hard-to-reach areas. They then spread from plant to plant, migrating from existing to newly sown plants. Aphids are winged females (Fig. 1B), adult thrips and whiteflies also fly from plant to plant, and mites are primarily carried by air currents. This dispersal results in a sharp increase in the number of phytophages on new, uninfested plants. On plants from other seeding lots, their density is approximately the same. Phytophage control on green crops is preventative. This involves the use of sticky traps and the release of entomophages. The selection of traps takes into account the pest population density, as well as the fecundity, searching ability, and target species of the entomophages. With interplanting, new plants are infested not only by pests but also by entomophages. Various species of parasites of the Aphidiidae family (Aphidius colemani, Lysiphlebus testaceipes, etc.) and predators—the larvae and adults of the ladybug (Cycloneda limbifer), the gall midge (Aphidoletes aphidimiza), the macrolophus caliginosus bug, etc.—can be used as aphidophages. Amblyseius cucumeris is used against thrips (depending on the population, from 50 to 150 individuals per 1 m2 per month), or Amblyseius swirskii is used against thrips and whiteflies. Stability of the entomocenosis is achieved by additional preventive introduction of entomophages onto new plants (Amblyseus species) or by laying out additional food (sittotroga eggs for macrolophus). While parasites control a single pest species, predators typically control several species. Cycloneda can be used when aphid populations are high, which often makes its use ineffective on lettuce crops, although it can also feed on mites and whitefly larvae.

During the spring and summer, to prevent the migration of insects from the greenhouse area, mowing is carried out, and in some cases, plants in the greenhouse area are treated with insecticides.

When preparing the salad complex for growing plants, a thorough disinfection of both the interior surfaces of the greenhouses and all equipment is carried out. When disinfecting hydroponic equipment, the system is first filled with a nitric acid solution (pH 2) for 8-12 hours to remove mineral and organic residues, then disinfected with a 1% solution of SID-2000 or 1-2% Hydrokey. Disinfect the interior surfaces of greenhouses and equipment with Virkon, Ecocid, or Kickstart using a cold fog generator (30-35 l/ha) or Virocid using a hot fog generator (1 l/1000 m³ of greenhouse volume). Disinfection of the interior surfaces of the greenhouse can be carried out with a 1% solution of Farmaiod or VRK. After such treatments, virtually sterile conditions are created in the greenhouse. However, nature abhors a vacuum, and fungi and bacteria, even non-pathogenic ones, enter the greenhouse, gaining a growth advantage without competition. As a result, they form colonies, and at high numbers, due to their release into the environment, they become phytotoxic to the crops being grown. Therefore, after rigorous chemical disinfection, a solution of Trichocin, SP 30 g/500 m2, or Gliocladin, SP 60 g/ha, containing the antagonist fungus Trichoderma harzianum, is applied to the surfaces of the greenhouses and equipment three days later. This allows the interior surfaces of the greenhouses and equipment to be colonized with beneficial microflora, preventing the development of newly introduced microorganisms. Overall, a controlled biosystem similar to soil suppression is created in the greenhouse. To maintain the condition during the green growing season, the same products are applied monthly to the greenhouse surface.

Despite eradication and preventative measures, plants in salad complexes are susceptible to diseases. This raises the question of what are the sources and routes of infection in salad greenhouses.

First, these are seeds, which can carry viral, bacterial, and fungal infections. Diseases appear immediately upon emergence (Fig. 3). Root rot is common; placing affected plants on a nutrient medium allows for the isolation of the pathogen in pure culture (Figs. 4 and 5). Before sowing, seeds are soaked for 1-2 hours in a suspension of Alirin-B, SP, or Gamair, KS (2 g per 1 kg of seeds) (the working fluid consumption is 1 liter per 1 kg of seeds), then dried and sown.

Secondly, irrigation water can not only be a source of infection but also contaminate nearby plants. In summer, when the temperature of the irrigation solution rises to 28-30°C, fungi of the genera Pythium and Aphanomyces rapidly multiply and accumulate in it, leading to massive loss of young plants. To prevent this, it is recommended to water in the morning and evening, use shade, and increase the dosage of Gliocladin, SP, Alirin-B, SP, and Gamair, SP by 1.5-2 times. Also, add hydrogen peroxide to the nutrient solution at a rate of 0.5-1 liter per 1 m³.

Thirdly, peat can contain not only pathogens but also fungi that produce phytotoxins. While the former include Fusarium sp., Pithium sp., Aphanomyces sp., Rhizoctonia sp., Erwinia sp., and Pseudomonas sp., the latter are primarily fungi of the Penicillium, Aspergillus, and other genera. The former cause rootworm, root rot, browning of roots and subsequent root death, stunted growth, and wilting of plants, among other things, with plants from the same seeding batch exhibiting identical symptoms. The disease manifestations are similar to those of seed infection. Substrate phytotoxicity leads to suppressed seed germination and inhibited plant growth and development (Fig. 6). In both cases, to suppress harmful mycoflora when growing lettuce on peat substrate, it is recommended to pre-apply Trichocin, SP at a rate of 30 g per 250-300 l of substrate. The use of the biofungicide Trichocin, SP allows for the disinfection of substrates during the seedling period and at the beginning of the growing season. The product is applied once during the substrate preparation stage using a sequential distribution. First, the entire volume of the product is mixed into 5 liters of substrate, then these 5 liters are thoroughly mixed with the main substrate. This ensures uniform distribution of the product throughout the entire volume. The resulting substrate can be used for sowing seeds and planting seedlings.

Phytotoxicity can occur due to technological improper cultivation practices, such as equipment failures during the preparation of the nutrient solution.

Fourth, the greenhouse area is a source of insect-borne viral infections and airborne pathogens that cause leaf diseases (anthracnose, septoria leaf spot, rust, cercospora leaf spot, gray mold, powdery mildew, ramularia leaf spot, downy mildew, etc.) (Fig. 7). The development of leaf spots and rots on green crops is facilitated by the high relative humidity found in greenhouses. The species composition and severity of diseases varies annually and is unique to each farm.

Protecting lettuce plants from a range of diseases relies on the use of biofungicides. These products are based on fungi of the genus Trichoderma and a complex of strains of the bacterium Bacillus subtilis. The advantages of biofungicides over common chemical fungicides include absolute safety, high efficacy, and no waiting period. Bioagents gradually suppress and displace phytopathogenic fungi and bacteria, so their application should be timely.

During the growing season, when replacing the nutrient solution with a new one, it is recommended to apply spore forms of bioproducts: Biofungicide for lettuce lines, SP, at a rate of 150-180 g per 1000 m² of lettuce lines; Alirin-B, SP modified – 20 g per 1 m³ of solution; or Alirin-B, SP + Gamair, SP – 10 g + 10 g/1 m³ of solution. Alternating products increases the effectiveness of bioprotection and maintains suppression of the lettuce root rhizosphere. The nutrient solution and substrate always contain the fungus Trichoderma, which can be detected by microscopy or by isolating it in pure culture (Fig. 8). Various types of algae also accumulate in the nutrient solution and substrate, giving the mineral wool its green color (Fig. 9). To suppress their development, add 0.5-1 liter of hydrogen peroxide per 1 m³ to the nutrient solution.

The contents of the jar of Biofungicide for Lettuce Lines should be dissolved in 3-5 liters of warm irrigation water (20-25°C) until a homogeneous suspension is obtained, then transferred to the nutrient solution tank.

To protect lettuce from spotting during the growing season, spray the plants with a suspension of Biofungicide for lettuce lines, SP - 50 g/100 l of water. Add 0.5-0.8% of Rapsol, 0.5-0.8% of Ecogel, or 0.5% of Narcissus to the solution.

Protective measures also include:

- Selecting disease-resistant lettuce hybrids. Currently, lettuce varieties resistant to virosis, downy mildew, and some adverse hydrothermal factors are available.

- Optimizing growing conditions (reducing relative humidity in greenhouses helps prevent recurrence of downy mildew and other diseases);

- the use of growth and development regulators that increase plant resistance to diseases and adverse factors, especially phytotoxicity, at a rate of 1-3 liters of Ecogel, 0.15-0.2 liters of Siliplant, 10 ml of Etamon, 50 ml of Zircon, etc. per 1 m³ of working solution. Biofungicides and other compounds can also be used in combination.

A lettuce protection system based on the use of biofungicides allows for the production of high-quality and safe products.

Candidate of Agricultural Sciences Trusevich A.V.