What to do if cucumber leaves are wilting in a greenhouse or in open ground

Growing cucumbers is an interesting and challenging endeavor. After all, these vegetables are demanding in terms of temperature and soil composition. A common problem for amateur vegetable growers is the sudden wilting of their foliage.

Loss of turgor is a common problem, and its causes are influenced by many factors.

Causes of leaf wilting

There are several causes of wilting foliage. Cucumbers are a sensitive crop and react poorly to both low and high temperatures. Furthermore, loss of turgor can be caused by an excess or deficiency of minerals, pathogens, or parasitic insects.

Under- or over-watering

The reasons that you should pay attention to first when a plant loses turgor are a lack or excess of moisture.

1. Insufficient watering is the first reason cucumber foliage wilts. This vegetable crop is very demanding when it comes to moisture. If the soil under cucumbers is insufficiently moist, the vegetative mass will lose turgor within a few hours. At the first sign of soil drying out, it should be watered immediately. If this is not done, the wilted leaves will dry out, fall off, and the plant will die within five to six days.
2. Excess moisture in the soil prevents cucumbers from obtaining oxygen. Plant roots, unable to breathe fully, fail to transmit oxygen to the leaves. Cucumbers gradually wilt, lose turgor, stop producing fruit, and soon die due to lack of oxygen.

Nitrogen deficiency or excess

Cucumbers are very demanding crops, requiring nutrients such as nitrogen and potassium. A deficiency in the soil will result in poor plant growth and wilting of the foliage. However, excess fertilizer also has a negative impact on the crop.

1. Cucumbers need nitrogen to actively grow vegetative mass. If the soil lacks it, the plant becomes depleted, and the foliage begins to gradually wilt. The plant loses its immunity and fails to set fruit.
2. If there's too much nitrogen in the soil, cucumber foliage will turn a rich green within the first three days. Then, the lower and middle leaves will curl and wilt. After 5-6 days, the foliage will turn gray-yellow, the fruits will become smaller, and the plants will become diseased and die.

Sun rays

The cucumber is believed to have originated in the subtropical regions of China and India. There, it still grows wild under the shade of trees, twining around them and out of the scorching sun.

Plants often become ill due to prolonged exposure to the sun. The foliage wilts under the scorching sun, the plant loses its turgor, and flowers fail to set fruit.

Pathogens and parasitic insects

Often, cucumbers' poor health is caused by attacks by parasitic insects that suck the plant's milky sap, as well as by fungal infestations. When attacked by pests, the lower portion of the plant begins to wilt, losing its turgor completely within a few days, and then dying.

1. Pathogenic microbes that can cause cucumber foliage wilting include downy mildew, fusarium wilt, white rot, and root rot. When affected by pathogens, the plant gradually loses turgor, and fruit does not set. Without timely control measures, the crop dies.
2. Parasitic insects that can cause leaf wilting include melon aphids, thrips, spider mites, and apple mites. If pests are not detected and controlled in a timely manner, plants rapidly lose turgor, become diseased, drop leaves, fail to set fruit, and die within 8-10 days of the pest's onset.

Dense plantings

Planting cucumbers too close together is often the cause of turgor loss. When planted too closely, the plants don't receive sufficient nutrients from the soil. The cucumber root system weakens, supplying little nutrition to the vegetative mass. This process weakens the plants, reduces fruit set by 80%, leaves wilt, and a harvest can be expected.

Why do cucumbers wilt in a greenhouse?

Most cucumber varieties and hybrids intended for growing indoors are highly resistant to diseases and adverse environmental factors. However, there are reasons why even resistant varieties can lose their turgor when grown in greenhouses. If cucumber foliage is wilting, it's important to identify the source of the problem and begin addressing it quickly.

1. Lighting problems. Cucumbers need 16-18 hours of daylight per day. If this is not the case, the plant begins to get sick and lose turgor.
2. Violation of nighttime temperature regimes. Cucumbers are a crop that requires a minimum nighttime temperature of 18 degrees Celsius. If this regimen is not met, the plant stunts growth, loses its immunity, sheds flowers, and the foliage wilts.
3. Excess or deficiency of minerals. If there's too much potassium in the greenhouse soil, mosaic spots appear on the foliage, leading to wilting and drying out. If the soil is oversaturated with copper, interveinal chlorosis develops on the lower leaves of cucumbers, leading to a loss of turgor throughout the plant. If there's a deficiency, the foliage turns pale, and the shoots become weak and limp.
4. Under- or over-watering. If the soil in greenhouses is under-watered, cucumbers will naturally wilt their foliage. However, if the soil is over-watered, the root system doesn't receive enough oxygen and doesn't supply it to the vines and leaves. Consequently, the plants begin to rapidly lose turgor.
5. Overheating. Although cucumbers are a tropical crop, they cannot tolerate daytime temperatures above 37°C (98°F). Air in the greenhouse that exceeds this temperature will contribute to a loss of turgor and immunity.
6. Pathogens and parasites. Aphids and spider mites pose a major threat to cucumbers grown in greenhouses. These parasites suck the milky sap of plants, leading to wilting of the leaves and the complete death of the plants. Pathogenic fungi also affect the health of cucumbers in greenhouses. If plants are affected by root rot, bacterial blight, downy mildew, and fusarium, foliar wilting cannot be avoided.

Combating leaf wilting with folk remedies

Wilting cucumber foliage leads to significant crop losses. Folk remedies can help gardeners prevent this problem while still producing organically grown vegetables.

Control of rot and verticillium wilt

Every gardener always has activated carbon and wood ash. These components inhibit the growth of rot and Verticillium fungi, which cause cucumber foliage to wilt.

Preparation

1. Crush 5 tablets of activated charcoal.
2. Add 1 cup of wood ash, 3 tablespoons of chalk, 50 ml of water to the powder.
3. Mix the ingredients until they form a mushy mass.
4. Apply the gruel to the base of the cucumber stems.
5. Disinfectants will prevent infection from entering the plant and slow down the rotting of the root system, which causes the foliage to wither.

Control of melon aphids and spider mites

An infusion of onion peel and hot pepper will serve as a repellent for sucking pests that cause the wilting of cucumber foliage.

Preparation

1. Pour 300 g of onion peel into 5 liters of hot water.
2. Add 1 crushed red hot pepper, 2 tablespoons of sugar.
3. Leave the mixture in a warm place for three days.
4. Strain the infusion and spray the plants once every 3 days.
5. The hot concentrated infusion will repel the pest, and the cucumbers will receive additional nutrition during the treatment with the onion peel solution.

Fighting powdery mildew

Powdery mildew, which causes leaf wilting, can be combated with a mullein infusion. As the manure ferments, it releases a gas that neutralizes harmful spores.

Preparation

1. Pour 4 kg of fresh cow manure into 5 liters of warm water.
2. Leave the solution in a warm place for three days.
3. Dilute the prepared concentrate with water 1:1 and spray the cucumber foliage every 2-3 days.
4. An infusion of mullein used to treat cucumbers will not only neutralize harmful spores but also saturate the plants with nitrogen.

Prevention

Preventative measures against the appearance of pests and pathogens that cause foliage wilting include:

• autumn treatment of soil with copper sulfate or Bordeaux mixture;
• treating cucumber seeds with Previkur or Fitosporin;
• When growing cucumbers in a greenhouse, provide sufficient ventilation for the plants;
• timely loosening of the soil and removal of weeds in the area under cucumbers.

To get a decent cucumber harvest, every gardener should be familiar with the potential problems associated with growing cucumbers and how to eliminate them.