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What Do Brown Spots On Sunflower Leaves Mean?

What Do Brown Spots On Sunflower Leaves Mean?

What do brown spots on sunflower leaves mean and do they affect the health of the sunflower plant?

Helianthus annuus L. commonly known as sunflower is a biennial herbaceous plant native to North America. It has been cultivated for its edible seeds, oil, and nutritious leaves and stems.

Sunflower is used as a source of vegetable oil, protein-rich food, and fodder. It is an important source of animal feed, including poultry, fish, swine, and dairy cattle. It also can be used as a green manure crop, a cover crop, and for erosion control.

Although sunflower is an important oilseed crop in many countries, it is grown on a much smaller scale in India compared with the USA, Canada, and China. The annual average production of sunflowers in India is about 2.5 million tonnes, while the production in the United States is more than 50 million tonnes. The production of sunflower oil in India was 3.9 million tonnes in 2012, whereas the production of sunflower oil in the USA was more than 80 million tonnes.

Sunflower oil is used in soap, margarine, cooking, cosmetics, and pharmaceuticals. It is also used in printing inks, paints, varnishes, and other industrial products. Sunflower oil has high levels of unsaturated fatty acids, such as oleic acid and linoleic acid which are important components of human diets.

It also contains vitamins A, B, and C, and minerals such as calcium, iron, phosphorus, magnesium, zinc, and copper. The nutritional composition of sunflower oil can vary based on the genetic variation of the plant and on the conditions under which it is grown.

Sunflower plants suffer from common diseases like brown spots on sunflower leaves.  Let’s look at what they mean and the effects they have on these plants.

What Are The Brown Spots On Sunflower Leaves?
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The brown spots on sunflower leaves are actually caused by a fungal disease known as sunflower chlorosis. Sunflower chlorosis is most commonly found in the western United States but has been seen in other parts of the country as well.

The disease causes leaves to turn yellow and eventually die. If left untreated, the disease can spread rapidly throughout a field and lead to large-scale crop losses. Fortunately, there are several ways to control sunflower chlorosis.

What Causes Sunflower Chlorosis? – Brown Spots On Sunflower Leaves?

Sunflower chlorosis is caused by a fungus known as Cercospora Kikuchi. The fungus spreads via wind-borne spores and infects the young leaves of sunflowers.

As the disease progresses, the leaves turn yellow and fall off. The disease tends to start on the lower leaves first and gradually move upward.

Sunflower chlorosis and powdery mildew are closely related diseases, but there are some key differences between the two. Sunflower chlorosis tends to occur more frequently and has more severe symptoms than powdery mildew. In addition, sunflower chlorosis can be controlled with fungicides that don’t work against powdery mildew.

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What Are The Best Ways To Control Brown Spots On Sunflower Leaves – Chlorosis?

The best way to control sunflower chlorosis is to apply a fungicide that is specifically designed to control this disease. Sunflowers should be sprayed at least twice a week, as long as symptoms are present. The best fungicides include:

Bordeaux mix

Bordeaux Mixture is one of the most effective sunflower fungicides. It is an emulsifiable concentrate with a unique formulation that includes a combination of copper and mancozeb. Copper is an effective foliar spray for controlling fungal diseases such as sunflower blight, and mancozeb can help prevent the spread of the fungus.

Mancozeb (Methoxychlor) is a systemic fungicide that can be applied to both pre-emergence and post-emergence to control a variety of fungal diseases. This product is generally used on early and late maturing sunflowers in the Northern US. Bordeaux mix is available in liquid form, which is easy to apply. This product is also effective against downy mildew.

Sun-cure

Sun-cure is a registered pesticide for sunflower that can be applied once per year as a pre-emergence treatment or twice during the growing season as a post-emergence treatment. It contains a combination of copper and sulfur that can be applied directly to the foliage to control sunflower chlorosis.

Sun-Cure works by inhibiting the growth of the pathogen that causes sunflower chlorosis. This product can also be applied in conjunction with a pre-harvest spray program to reduce the potential for seed-borne diseases. This product has been registered for use on all sunflower varieties and is available in both liquid and dry forms.

Copper sulfate

(CuSO4.) is an effective copper-based fungicide. It is effective against downy mildew, anthracnose, and sunflower blight. Copper sulfate is usually applied as a foliar spray to control downy mildew, sunflower blight, and anthracnose. It is most effective when applied early in the growing season.

The spray application should be repeated at least once during the growing season if the disease continues to be a problem. Copper sulfate is also used as a seed treatment. It is best applied at planting time or when the plants are flowering to help prevent the disease from spreading into the seed.

Copper sulfate is available in liquid and dry forms. It is available as a pre-emergence spray and can be applied in both organic and conventional crops.

Read more about Do You Know How Late Can You Plant Sunflowers?

What is wrong with my sunflower leaves?

Final Comments

The brown spots on sunflower leaves are an indication of fungal infection and the disease is highly infectious. The disease can be controlled by keeping the infected plants away from healthy ones. This can be done by covering the diseased leaves with a plastic sheet or wrapping them in paper for a small garden but you will need to spray a fungicide to spray a large garden.

Frequently Asked Questions

How do you get rid of fungus on sunflowers?

You can get rid of fungal infections of sunflowers by using the following methods. - Remove and destroy infected seeds, seedlings or plants. - Wash with a 10% bleach solution (1 part bleach to 9 parts water). - Spray with a fungicide, such as copper. - Sprinkle with lime or sulfur. - Grow in moist soil.

What is wrong with my sunflower leaves?

The leaves may look yellow, mottled, crinkled or puckered. This condition is called sunflower leaf scorch. Leaf scorch is caused by damage to the chloroplasts of the leaf cells. The chloroplasts are the part of the cell that makes food for the plant. In some cases, leaf scorch is caused by a disease, such as a sunflower mosaic virus or sunflower necrotic yellows virus. In other cases, it may be caused by environmental conditions, including drought stress, high temperatures, nutrient deficiencies, and high light levels.

What does fungus on sunflowers look like?

Fungus on sunflowers looks like small black dots or a white powdery substance on the leaves. Sunflower rust (Sclerotinia sclerotiorum) is a fungal disease that causes sunflower leaves to turn yellow, curl up, and drop off. This disease can also cause sunflower heads to become infected with sclerotinia rot and have poor yields.

How do you treat black spots on sunflower leaves?

Sunflower rust is most commonly treated by spraying fungicides, such as sulfur or copper. If sunflower rust has spread to sunflower heads, you can harvest the seeds and destroy them. You can also spray fungicide in the soil around the plant to prevent further infection.  If your sunflower head turns yellow, it may be infected with the sunflower chlorosis virus (SCV). Sunflower chlorosis virus causes sunflower heads to develop a light yellow color, have less than usual oil production, and have poor yields. You can remove the yellow heads and harvest the seeds, or you can destroy the heads by burning them.