Cucumber Plant Disease: Identification, Prevention, Treatment

Discover effective ways to identify, prevent, and treat cucumber plant disease in our insightful blog post. Safeguard your cucumber plants now!

Cucumbers are easy to grow and care for. However, during the cucumber growing process, you may encounter various pests and diseases such as leaf yellowing, leaf curling, root rot, bitterness, premature fruit rot, stem cracking, and more.

Xu Farm presents a comprehensive article on all types of cucumber diseases and their root treatments, equipping you with in-depth knowledge on this subject.

Cucumber Plant Disease

1- Seedling Damping-off Disease

Symptoms & Causes:

This disease is caused by the fungus Rhizoctonia solani during the seedling stage. The fungal infection results in damping-off of the seedlings, causing them to wither and the roots to rot. The primary cause is high moisture conditions that promote fungal growth in the soil. At this stage, seedlings are vulnerable, making them susceptible to the disease, ultimately hindering their growth, and sometimes, leading to their demise.

Prevention & Treatment:

It’s essential to thoroughly prepare the soil before sowing or planting seedlings. You can use various fungicides such as Anvil, Validacin, Copper-B, Bonanza, Rovral, Hinosan, or Tilt super for soil treatment.

2- Twisted Shoots and Curled Leaves Disease

Symptoms & Causes:

Symptoms of this disease include the twisting of young shoots, discolored and yellow-spotted leaves. In severe cases, the shoots become stunted, causing the plant to become stunted as well, resulting in reduced fruit production, often with deformed and bitter-tasting fruits.

Cucumber leaf curl, also known as gherkin wilt, is caused by piercing-sucking insects such as aphids, whiteflies, and cucumber beetles. Tiny bacteria, nymphs, and larvae, which are white or yellowish, reside primarily in young shoots or underneath young leaves, where they feed on plant sap, causing the plant to curl. During sunny weather, cucumber beetles hide in straw or rolled leaves.

Prevention & Treatment:

As this disease primarily affects plants during hot and sunny weather, it’s essential to pay attention to increasing the irrigation for the plants and preventing water deficiency or soil drought.

Maintaining an appropriate planting density and pruning affected leaves is also crucial.

To prevent and treat this disease, you can spray one of the following pesticides: Admire 50 EC, Confidor 100 SL, Danitol 10 EC, Vertimec 1.8 ND, Oncol 20 EC, Regent 5 SC, or Regent 800 WP.

3- Honey locust disease, yellowing leaves

Symptoms & Causes:

The initial symptoms appear as small dark spots along the stem of the plant, causing slight wilting during hot sunny weather. The characteristic feature is that the plant remains healthy in the morning and evening, but wilts during midday and afternoon; this marks the onset of the disease in cucumber plants. Just a few days later, the leaves start to wither and turn yellow, followed by the wilting of each branch, and finally, the entire plant suddenly wilts, resembling water stress, and eventually dies. This disease often inflicts severe damage when the cucumber plant is in full growth.

The main cause of this disease is hot and humid weather, water deficiency in the plant, and low soil moisture, which leads to the development of harmful fungi such as Fusarium and Phytophthora from the flowering stage to fruiting.

Prevention & Treatment:

Attention should be paid to ensuring well-draining soil and raising the beds to prevent waterlogging, creating soil that is both dry but still moist enough for the roots to absorb water and nourish the plants.

Maintain an appropriate plant density, avoiding planting too closely together. Prune and remove older leaves at the base and any side branches to ensure good ventilation and dryness in the cucumber garden.

Apply plenty of organic fertilizers like manure, rice husks, and straw. Maintain a balanced ratio of nitrogen, phosphorus, and potassium in fertilization, avoiding excessive nitrogen application.

Before planting seedlings, use granular pesticides like Bam, Basudin, Regent, Furadan, and place them at the base of the cucumber plants.

When detecting diseases, you can spray or irrigate with one of the following pesticides: Appencarb supper, Aliette, Bavisan 50WP, Benzeb 70WP, Copper-B, Carban 50SC, Derosal, Rovral, Ridomil, or Topsin-M at a concentration of 2-3%o at the base of the plants. When using pesticides, it is important to carefully read the manufacturer’s instructions for the correct dosage and application rate according to the cultivation area.

4- Leaf spot disease, powdery mildew, and downy mildew

Symptoms & Causes:

This cucumber plant disease is caused by the fungus Pseudoperonospora cubensis. The disease primarily affects the leaves, with white or pale yellowish fungal threads covering the underside of the leaves, which are the fungal spores. Within 3 – 4 days, the yellow spots on the leaves turn brown-black, the leaves wither and dry up, the stems of the plant dry out, and the plant sheds its leaves and dies. This disease causes severe damage during the flowering and fruiting stages, resulting in low yield and poor fruit quality, and it can even lead to plant death.

The disease typically starts on older leaves at the base and spreads to younger leaves. This harmful disease tends to thrive during periods of high humidity, heavy rainfall, and low temperatures around 18 – 20°C.

Prevention & Treatment:

Avoid planting cucumber alongside other crops like squash, pumpkin, and other vine plants. Raise the beds to ensure good drainage of the soil. Regularly prune and remove older leaves at the base and any diseased leaves, and eliminate plants showing signs of disease. When disease symptoms are detected, you can use some pesticides such as Benlate-C, Curzate, Copper-B, Daconil 500 SC, Mancozeb, Ridomil, Metalaxyl Zineb, or Viroxyl 58 WP to eradicate the fungal infection.

5- Root rot disease

Symptoms & Causes:

The first symptoms of the disease appear near the ground level on the stem, with small black spots, which then quickly spread and envelop the root collar, causing the plant’s stem and leaves to wither. Approximately one week later, the roots and the base of the plant become rotted, and the plant collapses and dies.

Root rot disease is caused by various harmful fungi such as Fusarium solani f.s. phaseoli, Rhizoctonia solani Kuhn, and Thielaviopsis. This disease thrives in conditions of heavy rainfall, high humidity, excessive moisture, low temperatures, or unusual temperature fluctuations. It is often associated with waterlogged soil.

Prevention & Treatment:

Pay close attention to soil preparation by applying lime, organic fertilizer, and potassium 10 days before planting. Raise the beds to ensure good drainage, and maintain a moderate planting density.

In case of excessive rainfall, mound the soil around the base of the plants to prevent waterlogging and flooding.

When the disease appears, you can use one of the following pesticides like Ridomil MZ72 WP, Rovral 50%, or Topsin M (50-70 WP) for spraying on the plants.

6- Fruit rot disease

Symptoms & Causes:

This cucumber plant disease affects the leaves, fruits, and stem base, with affected areas showing signs of waterlogging turning black and rotting. The disease typically appears during the flowering and pollination stage, targeting leaves, flowers, and young fruits. Within a period of 5 – 7 days after flowering, the disease causes the fruits to rot, young fruits to drop, or become deformed. In severe cases, it can even lead to root rot and plant death.

Fruit rot disease is caused by the fungi Choanephora cucurbitarum or Phytophthora sp. This disease causes significant damage, especially during rainy seasons.

Prevention & Treatment:

Due to the disease primarily affecting during the rainy season when temperatures and humidity are low, it’s essential to pay attention to the amount of water irrigation for the plants. Avoid overwatering, which can lead to waterlogging of the soil. Ensure the soil is well-drained and has good water drainage.

If disease symptoms are detected, limit watering in the afternoon. Spray one of the following pesticides such as Aliette, Curzate, Manzate, or Ridomil on the plants every 7 – 10 days.