Why Are Cabbage Leaves Turning Yellow? (Quick Answer)
If cabbage leaves are turning yellow, you need to find the cause of the disease as soon as possible so that it is easier to deal with it.
Yellow cabbage leaves indicate various problems: a lack of nutrients in the soil, improper watering, or the presence of diseases and pests. Many of these problems are easy to fix if you follow the advice in this article.
|Causes of Cabbage Leaves Turning Yellow|
|1. Potassium deficiency|
|2. Insufficient watering|
|4. Insect pests|
|5. Burns from pesticide|
Causes of Cabbage Leaves Turning Yellow
1. Potassium deficiency
Signs of potassium deficiency:
- the cabbage seems unhealthy
- edges of the cabbage leaves turn yellow.
Yellow leaves on cabbage are mainly caused by a potassium deficiency present in the soil. Usually the lack of potassium affects young cabbage seedlings, which cannot grow normally in the garden, more than adult cabbage.
If you find that the edges of the cabbage leaves and the tops of the cabbages turn yellow and the whole plant looks scorched and tired, rather carry out potassium top dressing.
How to fix Potassium deficiency
- Add potassium sulfate between cabbage rows on the soil at the rate of 10–15 g per 1 m², then water the soil.
- 10–15 g of potassium sulfate are mixed with 10 liters of water, mixed thoroughly until completely dissolved and watered with this solution every 1 m² of cabbage beds.
Instead of mineral fertilizers, you can use furnace black and vegetable ash, powdering the surface of the soil under each cabbage seedling (1 cup of wood ash for each square of plantings) and watering the beds after that.
Is Nettle Fertilizer good for vegetables like tomatoes? The answer to this question lies in this article!
2. Insufficient watering
Insufficient watering or the lack of watering is the second most common cause why cabbage leaves turn yellow. Cabbage like all cruciferous plants is a water-loving crop.
In hot weather or summer heat it is extremely important to maintain a water routine and water 2-3 times a week in order to prevent cabbage leaves from yellowing and drying. If you water your plantings only on weekends, then, most likely, yellow leaves signal a lack of moisture in the soil.
Another sign of insufficient watering is the simultaneous wilting of the cabbage outer leaf plates.
For cabbage, both a lack of water and its stagnation, leading to rotting of the roots, are harmful.
Insufficient watering of cabbage is harmful in the same way as excessive watering, its leaves wither, turn yellow, dry.
It is necessary to water 2-3 times a week, otherwise the heads of cabbage dry out and also lose the ability to recover.
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How to fix Insufficient watering
Start to water the cabbage roots through a drip irrigation system so you don’t have to come to the planting site every day. Adjust the drip irrigation system so that there is enough water in the water tank for at least one or two weeks.
In the summer cabbage requires to be water every 3 days with at least 2 liters of water under the crop. Using the sprinkling method means that you can water the cabbage soil bed directly from the hose over the leaf.
Also try to loosen the soil and mulch with a layer of straws to capture the moisture in the soil thus preventing it from evaporating under the sun heat.
Fusarium leaf wilt is a fungal disease that causes the development of yellow leaves on cabbage. First the cabbage veins turn dark then then clearly defined yellow triangles form at the leaf edges, and then all the cabbage leaves turn yellow and die.
To recognize this disease cut off the cabbage veins and observe brown dots on it.
Fusarium is a fungal disease that hibernates in the soil and remains in a latent state until the temperature has a range of 77-90°F (25-32°C).
Fusarium symptoms always depend on the cabbage variety and soil temperature and it might take from 2 weeks up to 2 months for the cabbage to die.
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How to fix Fusarium
Plants on which signs of a fungal disease are found are destroyed, and the soil is treated with copper sulfate (5 grams per ten liters of pure water).
Before planting cabbage carry out pre-sowing treatment of seeds and for the next years, grow varieties and hybrids that are resistant to Fusarium.
Downy mildew is the second disease that cause cabbage leaves to turn yellow. Young cabbage plants are susceptible to this and the leaves, especially those at the base, become covered with yellow spots on their upper surface .
These spots correspond to the existence of a greyish down lying symmetrically on the underside of the same leaf. The leaves can then turn yellow over their entire surface, become necrotic and die
If primarily affects the cabbage seedlings and if it is not treated quickly the lower leaves turn yellow and fall causing the death of the plant.
To prevent this disease you need to apply copper sulfate to the seeds and after planting to the seedlings. Space the plants to avoid too high densities which prevent air circulation and maintain humidity levels favorable to the development of the disease.
The third disease that affects the cabbage leaves is also fungal and it is called clubroot. It is manifested by growths and thickenings that appear at the cabbage roots. Clubroot prevents the nutrients from the soil from getting to the leaves and head of cabbage and as a consequence the leaves are turning yellow and fall off.
Cabbages that are affected by this disease can not be saved and need to be removed and burned and the soil treated.
How to fix Clubroot
Clubroot will remain in the ground for up to 5 years, so it is recommended not to plant any cruciferous vegetables including cabbage in that place.
The soil in the places of infection must be treated with a solution of ash and lime.
However, if you want to revive the cabbages try to remove the growths and separate the root part from the stem and water the plants abundantly.
If you do not succeed, burn the affected cabbage, and when digging, fertilize the soil with ash at the rate of 500-700 g per 1 square meter.
4. Insect pests
The reason for the cabbage leaves turning yellow can be burrowing or leaf-eating pests. It is important to quickly treat the cabbage with chemical or biological solutions.
|Leaf-eating pests that cause cabbage leaves to turn yellow|
|1. Cruciferous flea|
|2. Stem weevil|
|3. Cabbage spring fly|
Leaf-eating pests such as cabbage aphid or cruciferous flea, cabbage fly or stem weevil are damaging the cabbage with bites and holes they create when they feed and as a result the cabbage dries out. That’s why it is important to inspect the cabbage leaves when holes appear on them.
These leaf eating pests stay under the leaf blade and feed on the sap of cabbage, which is why at first dots and eaten passages appear on the leaves, and then they turn yellow and dry out.
To combat this pests you need to remove all the weeds which serve as a home for these pests and make infusions of garlic, onions or marigold and treat the cabbage leaves with it. Also sprinkle the cabbage soil beds with wood ash and crushed tobacco leaves.
|Burrowing pests that cause cabbage leaves to turn yellow|
|1. White grubs (Maybug)|
If healthy cabbage suddenly start to turn yellow and no holes or bites are seen on the leaves try to inspect the root and the soil around the roots. If damage to the roots are found then this is because of the burrowing pests like: white grubs, wireworms and nematodes.
To remove burrowing pests you need to treat the soil with a weak solution of potassium permanganate or use modern insecticides.
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5. Burns from pesticide
Spraying cabbage leaves with highly concentrated pesticides or other chemicals solution can get the leaves burned and afterwards turning yellow.
This is usually caused by exceeding the indicated dosage when using pesticides or neglecting the manufacturer’s recommendations about the time of day and air temperature.
If the fungicide or pesticide treatment was performed in the middle of the day when it is hot outside, the cabbage leaves may get burned and in order to prevent this it is recommended to be carried out in the evening.
How to fix Burns from pesticide
- Cut the affected yellow leaves from the cabbage.
- Water the cabbage with more frequency.
- Stop the treatment of pesticides for a few weeks.
How to Prevent Yellow Leaves on Cabbage
Most cabbage growing problems are easier to prevent than to fix. These steps will prevent cabbage leaves from turning yellow:
- Avoid planting diseased cabbage seedlings because it can infect the soil for several years;
- Loosen the soil to provide oxygen to the cabbage roots;
- Keep the soil moisture by watering regularly with warm water;
- Protect young cabbage seedlings from sudden temperature fluctuations;
- Avoid soil waterlogging;
- Apply organic fertilizer to the soil before planting the cabbage;
- Use insecticides and pesticides to keep the pest away;
- Use crop rotation techniques before planting;
- Remove weeds in time, loosen and mulch the soil.
As you can see, cabbage leaves can turn yellow and fall for various reasons. This issue can be avoided if prevention is not forgotten, starting from the seed stage.
You can treat disease by using prevention methods like : space the cabbages, do not water by sprinkling during the development of the cabbage and carry out a long crop rotation.
If temperatures are higher than 25°C the leaves may begin to turn yellow due to lack of moisture.
Take 20 grams of fertilizer based on potassium humate and dissolve it in 10 liters of water. For the first top dressing, which is carried out 16 days after transplantation, a solution of 10 liters of water, 20 g of superphosphate, 10 g of urea and the same amount of potassium supplement is used.