Agricultural practices for cultivation and plant protection of cucumbers against diseases and pests

During emergence, cotyledons can be eaten by slugs, so it is better to immediately cover the sown seeds with jars or halves of plastic bottles.

If yellow spots appear on the cotyledons, it is bacteriosis; the pathogen was on the seed coat, and it is better to remove the plant immediately than to struggle against bacteriosis the whole time later.

The root system of the cucumber is weak – the slightest soil disturbance causes the suction hairs to break. Therefore, weeds should be cut at the soil level (this inhibits their further growth) rather than pulled out. The soil under cucumbers should not be loosened, and if it compacts after irrigation, it should be mulched (covered from above) with peat.

Irrigation must be constant and uniform. Soil moisture in the root zone should not be allowed to dry out. Do not irrigate with cold (below 20 degrees) water. Abundant irrigation should be done weekly so that the soil is wetted to a depth of about 20 cm. In dry and hot weather, irrigation must be performed twice a week.

☝You should not irrigate cucumbers a little bit daily, because this will lead to the root system not growing deep, but instead remaining right at the soil surface.

With the slightest drying out of the soil, such a root system will dry up, and the plants will start to wilt due to a lack of moisture. Using hydrogel during cucumber sowing will save you from these problems.

In case of large temperature fluctuations between day and night, heating of high greenhouses is required at night; otherwise, the young fruits will stop growing, and bitterness will appear in the mature fruits. Furthermore, the plants should be top-dressed with calcium nitrate.

Diagnostics of nutrient deficiency and methods for their elimination:

• If the leaves are too pale and small (nitrogen deficiency): top-dress with manure (1:10), weed infusion (1:5), urea, or ammonium nitrate (2 tablespoons per 10 l of water).
• If a brown edge appears on the margins (potassium deficiency): apply potassium top dressing (3 tablespoons of any potassium fertilizer that does not contain chlorine per 10 l of water or sprinkle half a cup of ash around the plants).
• If the leaves are directed upwards (phosphorus deficiency): top-dress with superphosphate (3 tablespoons per 10 l of water).
• If the leaves have a marble dark and light green color (magnesium deficiency): dilute dolomite (1 cup per 10 l of water) and water the soil around the plants with this white "milk."
• If the leaves have acquired a yellow-green color (micronutrient deficiency): top-dress the plants with micronutrients, whichever you have, by dissolving them according to the provided instructions. It is easiest to use "Uniflor-micro" (1 teaspoon per 5 l of water).

All these top dressings should be applied in the evening after irrigation.

However, it is most effective in all these cases to provide foliar top dressing with a solution of "Uniflor-rost" or "Uniflor-buton" (2 teaspoons per 10 l of water). These fertilizers contain nitrogen, phosphorus, potassium, magnesium, and another 18 micronutrients in chelated form, which allows plants to quickly absorb all these elements. "Uniflor" products are a real "first aid" for plants.

Pay attention to the leaves: if a light border appears on the young leaves, there is a high threat of downy mildew disease, which develops quickly at excessively high air and soil humidity, especially in cold weather.

On mature leaves, yellowish oily spots appear on the upper side along the veins, with a whitish-violet coating on the underside of the leaf. The oily spots begin to dry out, gradually covering the entire leaf blade. The process of infection and leaf desiccation is very fast; in just a few days, all the plants in the greenhouse look as if it is deep autumn.

Naturally, there can be no talk of any fruiting. At the first signs of the disease:

• stop irrigation;
• ventilate the greenhouses well;
• cover the soil under the cucumbers completely with ash or chalk to dry it out;
• leaves with oily spots and those that have dried out must be removed and burned.

Spray healthy leaves with "Fitosporin" or a bright pink solution of potassium permanganate to prevent their infection. Soil-grown cucumbers can be sprayed with the preparation "Ridomil-MC". This is a chemical poison, so after treatment, the cucumbers can be harvested no earlier than in 20 days.

In cold or cool weather, cucumbers should be irrigated moderately; this will protect them from disease not only from downy mildew, but also from rots.

The most common disease of cucumbers in greenhouses is bacteriosis. Angular yellow spots initially appear on the leaves, which then dry out and crumble away. On the underside of the leaf, cloudy pinkish droplets of liquid are visible. Similar cloudy droplets appear on sores on the fruit.

In humid weather the disease intensifies sharply. Despite the fact that cucumbers are sensitive to drafts, it is necessary to ventilate the greenhouses constantly, because cucumbers fear bacteriosis and stem rots even more than drafts. The humidity of the air and soil should not exceed 90%.

It is usually recommended to spray plants affected by bacteriosis with Bordeaux mixture (1 teaspoon per 5 l of water), but it is undesirable to use it in greenhouses, since the cucumbers cannot be eaten for 20 days. It is better to use "Phytosporin", "Zircon", or garlic infusion (pour 5 l of water over 200 g of chopped garlic leaves and scapes, cover, let steep for 4 hours, and spray the leaves from underneath immediately).

Ventilate the greenhouses more often, reduce irrigation, apply top dressing to the cucumbers with an infusion of fresh manure or an infusion of weeds, and provide additional potassium top dressing. A good result is provided by preventive spraying of healthy leaves with "Epin-extra" or "Novosil" ("Silk"), "Ekoberin" preparations, but the best preventive measure is a protective cocktail:

Shake the specified ingredients in 100 ml of water until completely dissolved, then add 900 ml of water.

Another quite common disease is anthracnose. The disease manifests on the leaves—rounded brown spots form on them, which then crumble away. Deep rounded sores with a hard edge, resembling bird pecks, appear on the fruits.

Recommendations for plant protection:

• In greenhouses, you can only use "Phytosporin", "Zircon", or potassium permanganate. After spraying with the latter, it is advisable to dust the damp leaves with ash, or even better, with dry mustard.
• Cucumbers grown in open soil can be sprayed with Bordeaux mixture (1 teaspoon per 5 l of water), but after this, the cucumbers cannot be eaten for 20 days, or you can use "Phytosporin".

If the stems or leaf stalks become soft and are covered with a white bloom, the cucumbers have contracted white rot. High humidity (above 90%) combined with sharp temperature changes, prolonged cold spells, irrigation with cold water, and stagnant air in dense plantings contribute to the appearance of this disease.

Algorithm for saving the plants:

1. Immediately apply a foliar top dressing: 1 teaspoon of urea, 1 granule of copper sulfate (or "Khom" on the tip of a knife) per 10 l of water.
2. Stop irrigation, ventilate the greenhouses, and remove diseased fruits and leaves.
3. Remove the bloom with a dry cloth or one dampened in a crimson solution of potassium permanganate, dust with ash, or smear with a paste made of chalk, potassium permanganate, and water. The paste should be pink in color.

Do not delay in removing the bloom, otherwise, stem rot will girdle the stem—the upper part of the plant above this point will die.

Sometimes in greenhouses, the entire plant is observed to wilt. This is either a viral disease—wilt (Verticillium wilt), in which case the plant should be removed so that sucking insects do not transfer the disease to others. Or, the wilting is caused by root rot.

Order of actions in case of wilting:

• First, carefully scrape the soil away from the roots.
• If the root collar is frayed, brown, or rotten, it is root rot. Often, root rot occurs where manure is used as a bio-heating layer. The top layer of soil must be completely removed.
• Water the roots with a crimson-colored solution of potassium permanganate or a solution of "Khom" (1 incomplete teaspoon per 1 l of water).
• Remove the stem from the vertical trellis, lower the bottom end onto the soil in a ring, and tie it to the trellis again. Cover the ring of the stem lying on the soil with fresh, nutrient-rich soil, moisten it well, and ensure it does not dry out. New roots will appear on the buried part of the stem, and the plant can be saved.
• If the unearthed roots look perfectly normal, but the plant is wilting, then it is wilt.

Often, a network of tiny holes forms on the upper leaves of cucumbers growing in a greenhouse—these are holes caused by sunburn from drops of night dew that fell from the plastic film onto the leaves.

The main pest of cucumbers is the spider mite. When it infests a leaf, it sucks out its juices, causing the leaf to turn pale, then yellow, and eventually die. The mites are very small and can only be clearly seen under a magnifying glass. They live on the underside of the leaves.

Methods of controlling spider mites:

• Spraying with the preparation "Fitoverm" (or "Iskra-bio"). This biological preparation is absorbed by the leaf and protects the plant from all sucking and chewing pests for 3 weeks.
• Using garlic infusion (spraying must be carried out on the underside of the leaves).

One should not use chemical poisons, as after such treatment the cucumbers cannot be used for food for 20 days.

In the second half of summer, cucumbers can be attacked by black melon aphid. Against it, one should also not use toxic chemicals; it is better to use:

• Green soap;
• Potassium permanganate solution;
• Conifer needles;
• Garlic and other home remedies.

The fact is that aphids have very delicate bodies, and even hot water will kill the aphids without damaging the plant. Or, as mentioned above, use "Zdorovyy Sad" or "Fitoverm".

The fruits have a pear-like shape – they have a swollen tip. This is a potassium deficiency.

The tip of the fruit is narrowed and bent like a beak, and usually the end lightens – this is a nitrogen deficiency.

The fruit has a "waist" (it is narrowed in the middle) – the reason is a large temperature difference between day and night, sometimes due to irrigation with cold water.

The cucumbers are crooked, with an irregular arch-like shape – cross-pollination of hybrids by insects has occurred. Such cucumbers should be harvested immediately and used in salads. In cultivars, this phenomenon is observed when the soil dries out or irrigation is uneven: either too dry or too wet.

Cucumber fruits react sharply to any deviations from the optimal microclimate in the greenhouse. Under unfavorable conditions, the fruits may stop growing completely or shed their fruit set. Most often, growth stoppage occurs during cold nights, as well as with a deficit of moisture in the soil and air.

When cucumber fruit sets turn yellow, do not develop, dry out, and fall off, it means that fertilization has not occurred. In a greenhouse, the process is disrupted due to excessively high temperature and humidity, or during prolonged rains when pollinating insects do not fly. With a cluster type of fruiting, the drying of some fruit sets has a different cause — due to a nutrient deficit, only part of the fruits develop, and the rest dry out.

• Temperature in the greenhouse for pollination failure — above 36 °C
• Air humidity for pollination failure — above 90 %
• Development of fruits in a cluster with nutrient deficit — 1–2 pcs.

Causes of bitterness in fruits and methods of controlling it

Bitterness in cucumbers is caused by an increased concentration of cucurbitacin. This valuable element possesses proven anti-tumor effects, but it spoils the marketable appearance of the produce. The plant begins to actively accumulate it during any stress situations.

To reduce the stress level in plants, it is necessary to timely adjust mineral nutrition. Upon the onset of extreme weather conditions, provide the plantings with top dressing of calcium and potassium nitrates. Additionally, treatment with stimulants will help strengthen the plants' own immunity.

Modern cucumber breeding is solving the problem of cucurbitacin accumulation at the genetic level. Today, this is one of the key directions in the work of breeding centers. Growing new hybrids and cultivars without bitterness allows for guaranteeing the harvest quality in any weather.