Application of chemical and biological plant protection agents in greenhouses

Chemical preparations and biological agents for plant protection

Plant decoctions and infusions do not always cope with pests in a greenhouse. They work as a preventive measure or in cases of minimal infestation of plantings. If pests have multiplied en masse, it is necessary to use specialized insecticides of chemical or biological action.

A number of effective preparations are permitted for protecting plantings in home gardens. They are selected depending on the specific problem — for destroying insects or for controlling diseases.

• Against harmful insects: "Bankol", "Decis Extra", "Inta-Vir", "Karate", "Karbofos", "Mospilan", "Regent 25", "Sonet", "Fas", "Fury", "Phytoferm", "Ciperchans", "Sherpa".

• Against diseases (fungicides): "Agat", "Bordeaux mixture" (Bordeaux liquid), "Vectra", "Topaz", "Fundazol", "Kartotsid".

Protective measures are planned in advance, focusing on the phytosanitary situation of previous seasons. Pest control begins with agrotechnical prevention, after which biological methods are involved. Natural predators and parasites (entomophages) are capable of quickly suppressing pest reproduction centers without the use of chemicals.

1. Assess the phytosanitary situation of the previous season and identify overwintered pests and diseases.
2. Begin protective measures with prevention and strict adherence to agrotechnical requirements.
3. Apply a biological control method using natural enemies of pests (entomophages).

Beneficial insects that are advisable to breed on the site for pest control include the lacewing, Trichogramma, ground beetle, and Phytoseiulus. During their development period, lacewing larvae destroy thousands of scale insects, aphids, and spider mites, and the predatory mite Phytoseiulus specializes in spider mites. The tiny wasp Trichogramma destroys pests while they are still in the egg stage.

• Release of Trichogramma — 50—60 thousand individuals/ha
• Development period of lacewing larvae — about 60 days
• Efficiency of ladybug — 4000—5000 thousand aphids
• Daily ration of ground beetle — about 10 caterpillars and 100 larvae

Below is precise data on the effectiveness of beneficial insects, confirmed by practice. The five-spot ladybug controls aphid colonies, and the ground beetle actively eradicates caterpillars and larvae in the soil and on plants.

Beneficial insect	Pest eradication efficiency
Five-spot ladybug	adult destroys about 4000—5000 thousand aphids

Ground beetle food source	Quantity per day, pcs.
Caterpillars	about 10
Larvae	100

Infectious plant diseases and their pathways of spread

All diseases of greenhouse crops are divided into infectious and non-infectious (physiological). Physiological disorders are not transmitted from plant to plant and arise due to nutrient deficiency, lack of moisture, or an unsuitable light regime. Infectious diseases are caused by pathogens: fungi, bacteria, and viruses.

The most common infectious diseases in greenhouses include gray mold, blackleg, powdery mildew, downy mildew, as well as rots of the stem base, roots, and bulbs. Viral infections pose a particular danger. Viruses are transmitted with infected seed, are carried by sucking pests (aphids, thrips, leafhoppers, mites, bugs), and are also transmitted mechanically via the sap of diseased plants during transplanting, tying, pruning, and side-shoot removal.

Symptoms of viral infection manifest as leaf mottling, yellowing and crinkling, as well as stunting of the entire bush. Upon detecting the first signs, affected plants must be controlled, focusing on characteristic visual manifestations of diseases.

• Cucumber mosaic: alternating green and light yellow spots on leaves, glassiness of vines.
• Tomato mosaic: alternating light and dark green areas on leaves, green and red spots on ripening fruits.
• Tomato streak: dark streaks and stripes on stems, petioles, and fruit stalks, curling of leaves.

Prevention of viral and bacterial infections

It is almost impossible to treat viral infections in plants, as viruses develop directly inside the cells. The only reliable way to protect a greenhouse is to prevent the emergence of the disease. At the first symptoms of infection, immediately remove and destroy diseased bushes, especially if signs appear during the early stages of the growing season.

For the sowing of cucumber and tomato, use only healthy seed material. Never sow seed collected last summer. For reliable prevention, use seed after long-term storage at room temperature and be sure to perform their disinfection.

• Shelf life of cucumber and tomato seed — from 2 to 4 years
• Potassium permanganate solution concentration — 1%
• Seed treatment time — 30 minutes
• Mixing ratio — 1 g of preparation per 100 ml of water
• Quarantine period for neighboring beds — 2–3 years

To prepare the disinfectant solution, dissolve potassium permanganate in half a glass of water. The resulting liquid will be nearly black, and the treated seed will turn completely dark after soaking. After the procedure, rinse them with clean water and let them dry.

Bacterial infections penetrate plants through stomata, nectaries, or mechanical damage to stems and leaves. Pathogens persist in the soil and on plant debris, and are spread by insects, nematodes, or water splashes during irrigation. Particularly severe forms of bacteriosis develop when bacteria enter roots damaged by nematodes or infect the plant's vascular system. In greenhouse conditions, angular leaf spot and bacterial wilt of cucumber pose the greatest danger.

• Angular leaf spot of cucumber. Transmitted with plant debris and affects seedlings. Light brown spots appear on cotyledons, while angular oily spots appear on leaves, which then dry out and crumble. Ulcers with a sticky yellowish exudate form on vines and fruits.
• Bacterial wilt of cucumber. Carried by seed and causes wilting of stems and leaves during the flowering and fruiting period. Reddish-brown spots with an oily halo and a zone of chlorosis form on the leaves.

How to stop the spread of clubroot of cabbage

Clubroot is a dangerous fungal disease affecting all types of cabbage, as well as radish, black radish, turnip, rutabaga, watercress, and mustard. Most often, the pathogen is brought onto the plot along with purchased transplants. Cauliflower and early white cabbage are particularly susceptible to infection.

When infected, white galls of various sizes form on the roots of the plants. If the transplants were infected initially, large swellings form on the taproot. When healthy plants are planted in infested soil, small bead-like galls form on the lateral roots. By autumn, these thickenings rot and disintegrate, releasing millions of viable spores into the soil.

It is impossible to completely clear the ground of clubroot spores, but you can localize the infection focus. When harvesting on an infected plot, strictly observe sanitary rules.

1. Carefully collect all affected roots from the bed.
2. Remove infected remains beyond the plot boundaries and destroy them.
3. Designate separate tools for working on this bed and do not use them on clean areas.

To avoid mixing infested soil with clean soil, do not plough the affected beds and separate them with deep furrows. Spores remain viable in the soil for several years. During the first few years after detecting clubroot, refrain from planting susceptible crops in neighboring beds, as earthworms and slugs can spread the spores.

To gradually clear the soil, exclude the following crops and weeds from crop rotation on the infected plot:

• All types of cabbage;
• Radish, black radish, daikon, and turnip;
• Watercress and leaf mustard;
• Weeds of the Brassicaceae family: winter cress, wild radish, wild mustard, shepherd's purse, field pennycress.

Soil reclamation after clubroot and selection of resistant cabbage cultivars

When clubroot is detected in the beds, it is important to correctly adjust the crop rotation. The pathogen is not dangerous to crops of other families, so any vegetables other than cabbage can be grown on the infected plot. However, in the first years after infection, avoid planting root crops so as not to spread spores throughout the greenhouse along with soil particles. If the infection has covered most of the area, it is safest to swap the garden beds and the potato field for a few years.

Clubroot spores germinate most actively in acidic and excessively moist soil. Regular liming is required to neutralize the environment, as the soil quickly becomes acidic again. As an additional deacidification measure during the growing season, potassium nitrate or alkalizing organic fertilizers are applied.

• Maximum lime dose per bed — 200 g/linear meter
• Acidity of AVTEP organic fertilizer — pH 8.2
• Frequency of AVTEP top dressing during the growing season — 1–2 times
• Period for returning cabbage to the same spot — no earlier than 4–5 years
• Single dose of wood ash per planting hole — 30–40 g

When returning cabbage to the previous plot, exclude cauliflower and early cabbage from the rotation. Also, popular but highly clubroot-susceptible cultivars are strictly unsuitable. Instead, choose relatively resistant hybrids and cultivars of domestic breeding, adapting the planting scheme to the phytosanitary condition of the soil.

Cultivar group by maturity period	Relatively resistant cultivars (recommended)	Highly susceptible cultivars (avoid)
Mid-season	Losinoostrovskaya 8, Tayninskaya	Slava Gribovskaya 231, Slava 1305
Mid-late	—	Belorusskaya 445
Late	Zimnyaya Gribovskaya 13, Moskovskaya pozdnyaya 15, Moskovskaya pozdnyaya 9	—

When planting transplants, be sure to use barrier protection methods. They will help protect the young roots of the plants during their period of maximum susceptibility to soil infection. Adherence to planting technology minimizes the risk of crop infection at early stages.

1. Prepare planting holes in a bed cleared of weeds.
2. Apply sifted wood ash to each hole and thoroughly mix it with the soil.
3. If transplants were grown without a root ball, coat their bare roots in limestone flour.
4. Carefully plant the transplants into the prepared soil.

Control measures for anthracnose, downy mildew, and rots in the greenhouse

Anthracnose primarily affects cucumbers, peas, zucchini, pumpkin, and pattypan squash. The disease manifests as yellow-brown spots on leaves, weeping pink ulcers on stems and vines, and fruit shriveling. To prevent infection, it is necessary to work proactively and begin protection with seed treatment.

For seed disinfection before sowing, accessible plant and mineral solutions are used. Seeds are kept in the prepared mixture for 6 hours, after which they are dried until free-flowing. The treatment allows for the destruction of hidden infection on the surface of the seed coat.

• Aqueous aloe juice solution in a 1:1 ratio.
• Mullein solution in a 1:6 ratio.
• Ash solution at a rate of 20 g of ash per 1 L of water.

Gray mold, root rot, and downy mildew (peronosporosis) actively develop when the temperature and humidity regime in the greenhouse is disrupted. Gray mold affects brassicas, root crops, cucumbers, and tomatoes, appearing as a fuzzy bloom during storage. Downy mildew quickly destroys leaves in rainy weather, while root rot causes the death of the roots of cucumber transplants, tomatoes, and peas.

To protect greenhouse vegetables from the complex of rots and downy mildew, strictly follow general preventive measures. These actions will help minimize the accumulation of spores in the protected ground and strengthen the plants' immunity. Pay special attention to the quality of irrigation water and timely clearing of beds from plant residues.

• Water the plants only with warm water and avoid excessive air humidity.
• Heat the seeds before sowing to destroy hidden infection of downy mildew.
• Dose nitrogen top dressing, avoiding excessive vegetative growth.
• Timely remove and burn plant residues, weeds, and tops after the harvest.
• Carry out annual disinfection and mulching of the greenhouse soil.

Late blight. The most dangerous disease of tomatoes and other nightshade crops in the conditions of the North-West. The fungus appears on plants 10-15 days after infecting potatoes. First, the leaves get sick, then the fruits and stems, on which dark brown spots appear. Fruit disease is especially dangerous. Blurred oily brown spots form on them, rapidly increasing in size. Green fruits get sick more often, but fruits in the ripening stage also get sick quite frequently. Green fruits collected without external signs of the disease quickly turn black and rot during ripening. This is a consequence of the invisible penetration of the fungus into the fruit. Favorable for the development of the disease are high air humidity and moderately warm weather.

Among chemical agents, spraying plants with "Bordeaux mixture" is effective: 100 g of copper sulfate and 100 g of lime per 10 L of water. The treatment is carried out no more than 3 times, stopping 15 days before the harvest. One can also use "Polycarbacin" at a rate of 40 g per 10 L of water, stopping the treatment 20 days before the harvest.

At the end of the first ten days of August, after the completion of fruit formation, plants can be sprayed against late blight with a 25—30% table salt solution. Plants treated in dry, sunny weather shed leaves burned by the concentrated solution. A thin layer of salt covering the fruits during spraying prevents the penetration of the fungus. Under the sun's rays, the fruits ripen quickly, avoiding the disease. The best way to protect against the fungus is to use the earliest-maturing cultivars — Nevsky, Sever, Baltiyskiy, and others capable of avoiding the disease due to their early maturity periods.

Powdery mildew. The fungus affects cucumber leaves. Small, rapidly spreading white spots appear on the surface, gradually spreading to the underside. The disease intensifies during large temperature fluctuations. The parasite overwinters on plant residues. To combat it, plants are sprayed 4–5 times per season with a solution of colloidal sulfur at a rate of 20 g for open ground and 40 g for protected ground per 10 l of water.

Brown or olive spot. The disease manifests at lower temperatures. Cucumber fruits, leaves, and shoots are affected. Rapidly spreading, then cracking spots form on the fruits. In greenhouses, they become covered with a brownish-olive coating. The fruits change shape, curl, and rot quickly.

Control and prevention measures:

• The fungus overwinters on plant residues, so they must be removed and burned in the fall.
• To prevent the disease, plants are sprayed with "Bordeaux mixture" before flowering.
• Before sowing or planting transplants, the greenhouse and hotbeds must be disinfected.
• When growing cucumbers, maintain optimal temperature and humidity.

Bacteriosis. Affects cucumber, pumpkin, summer squash, and pattypan squash plants. Oily angular spots form on the leaves between the veins, later turning into holes. Especially in wet years, during severe infection, the entire leaf tissue is destroyed, except for the veins. Shoots and fruits are also affected. Watery spots form on them, turning into drying and sunken ulcers. The disease is transmitted via plant residues and seed, therefore infected plants are treated with a "Bordeaux mixture" solution.

Tobacco mosaic virus (TMV). Affects tomato plants in greenhouses. Mosaic spots of light and dark green color appear on the leaves. The tops curl or become strongly corrugated. The disease is transmitted by insects, leaf friction, as well as by human hands or clothing. Infected plants significantly lag in growth and develop poorly. Formed fruits often stop growing. The yield is significantly reduced.

Main control methods:

• In the fall after harvesting, all infected plants are removed and destroyed, and the top layer of soil is removed to a depth of at least 5 cm.
• All parts of the greenhouse are sprayed with a 0.5% solution of trisodium phosphate.
• Before entering the greenhouse, low boxes with sawdust are placed, which are systematically moistened with a disinfectant solution of the same preparation.
• Work clothes are thoroughly boiled in the fall, as the virus can persist on them for up to 3 years.

Blossom-end rot. The most common physiological disease of tomato in greenhouses and hotbeds. The disease manifests as dying tissues at the tip of the fruit, which gradually darken and dry out. The main cause of the disease is a lack of moisture in hot weather. The disease is detected 2–3 weeks after the plants begin to experience an acute lack of moisture in the lower soil layers. Sometimes this happens due to an excess of fertilizer or their high concentration. The disease can be observed in dry weather in open ground as well, especially in the south.

To avoid the appearance of the disease, it is necessary to systematically and evenly irrigate the beds to the full depth of the arable layer. In the greenhouse, one should not allow excessive air dryness, excessive temperature rise, and high concentration of fertilizers, especially mineral ones.

Fruit cracking. A physiological disease that manifests during sharp changes in soil moisture. Both green and ripening fruits crack. The rupture of the skin and tissue occurs due to excessive pressure inside the fruit. This is observed when the soil is excessively moistened after a long lack of moisture. A lot of water quickly accumulates in the fruits, and the skin, unable to withstand the pressure, ruptures. To prevent the disease, it is necessary to constantly maintain optimal soil moisture and a normal concentration of salts in the soil solution.

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