Wheat Rust

Wheat rusts, which are fungal diseases, have a widespread presence in almost every country where wheat is cultivated, leading to significant economic losses.

One concerning characteristic of rusts is their ability to generate new strains of fungi, enabling them to infect even previously resistant wheat varieties.

The infectious spores of the rust fungus are capable of spreading over long distances through wind dispersal. Under optimal weather conditions, they can quickly cause infections.

There are three types of rust diseases that affect wheat:

  1. Leaf rust: This type primarily attacks the foliage of the wheat plant.
  2. Stem rust: Stem rust forms on the stems and leaf sheaths of the plant, although it can also develop on awns, glumes, and seeds.
  3. Stripe rust: Stripe rust occurs on the leaves of the wheat plant, although it may also affect glumes and awns.

Leaf rust

Leaf rust, also known as brown rust, is caused by the fungus Puccinia triticina.

When infected, the leaves exhibit dusty, reddish-orange to reddish-brown fruiting bodies on their surface. These lesions produce a large number of spores, which can cover almost the entire upper leaf area.

Severe rusting of the upper leaves before flowering is particularly detrimental. It can lead to early defoliation, reducing the time available for grain filling and resulting in the production of smaller kernels. The grain may also experience shrinkage, as the nutrients produced, primarily in the flag leaf, are utilized by the fungal infection instead of being transported to the grain.

Early infection can weaken plants, hinder root and tiller development, and lead to significant yield losses.

The spores of leaf rust are primarily spread by wind and splashing water.

The optimal conditions for infection development include temperatures ranging from 59 to 70 degrees Fahrenheit (15 to 21 degrees Celsius) and a minimum of 6 hours of moisture on the leaf surface. New symptoms typically appear within around 10 days when the temperatures are favorable and moisture is present.

Stem rust

Stem rust, also referred to as black rust, is caused by the fungus Puccinia graminis f. sp. tritici.

The characteristic spots of stem rust have an elliptical shape and differ from those of leaf and stripe rust by being more elongated. These spots appear on both the lower and upper surfaces of the leaves and range in color from orange to dark red. The margins of stem rust spots have an irregular, ragged appearance.

When the pustules on the leaves are young, they release a large number of spores. As the growing season progresses, these spores darken, earning the rust its common name of black rust.

Severe infections can transform a healthy crop into a tangled mass of black stems just weeks before harvest, resulting in grain that is shrunken and diminished in quality.

The development of stem rust requires the warmest temperatures among the three types of wheat rusts, preferably ranging from 59 to 84 degrees Fahrenheit (15 to 29 degrees Celsius). It also necessitates 6-8 hours of moisture on the leaf surface. Under wet weather conditions and optimal temperatures, new lesions can form within 7-10 days.

Spore production occurs in multiple cycles throughout the growing season.

Stripe rust

Stripe rust, also known as yellow rust, is caused by the fungus Puccinia striiformis f. sp. tritici.

When infected, the wheat leaves develop yellow or orange blister-like pustules that align parallel to the leaf veins. These lesions generate a large number of spores, which can be easily dislodged and dispersed by wind.

In the case of severe stripe rust infections, susceptible varieties can experience crop losses of up to 100% if the disease emerges early in the season, particularly under wet and cool weather conditions.

Walking through heavily infected fields may result in the spores leaving an orange dust residue on clothing.

In environments with lower humidity, stripe rust spores have greater freedom to disperse into the air and can travel long distances.

Stripe rust tends to appear earlier in the season because its development is enhanced by the cool and moist weather that typically prevails early on.

The disease thrives under ideal temperatures ranging from 45 to 54 degrees Fahrenheit (7 to 12 degrees Celsius) and requires 6-8 hours of leaf moisture for its progression.

Multiple cycles of spore production occur throughout the growing season.

Management Strategy

To mitigate losses caused by wheat rust infections, various methods are implemented.

The timely management of the disease is of utmost importance.

Chemical control

The following fungicides are recommended for the prevention and eradication of bean rust:

  • JUPITER 125SC: Mix 15ml with 20 liters of water.
  • BRADLEY 500SC: Mix 10mk with 20 liters of water.
  • DOMAIN 250EC: Mix 10ml with 20 liters of water.
  • DUCASSE 250EW: Mix 20ml with 20 liters of water.
  • EXEMPO CURVE 250SC: Mix 15ml with 20 liters of water.
  • EXPLORER 3SL: Mix 10ml with 20 liters of water.
  • MILESTONE 250EC: Mix 10ml with 20 liters of water.
  • MILLIONAIRE 690WDG: Mix 40g with 20 liters of water.
  • PROVIDENCE 400WP: Mix 50g with 20 liters of water.
  • RANSOM 600WP: Mix 15g with 20 liters of water.
  • TOMAHAWK 250EC: Mix 10ml with 20 liters of water.
  • TRINITY GOLD 425WP: Mix 50g with 20 liters of water.
  • COLONIZER 440WP: Mix 50g with 20 liters of water.
  • DEFACTO 500EC: Mix 20ml with 20 liters of water.
  • ABSOLUTE 375SC: Mix 10ml with 20 liters of water.

Non-chemical control

  • Implementing crop rotation with non-host plants or members of the Gramineae family.
  • Maintaining field sanitation and hygiene by removing debris, which serves as a primary source of inoculum and helps reduce infections in subsequent crops.
  • Opting for resistant or tolerant varieties of beans.
  • Proper weed management practices.
  • Planting certified or disease-free seeds.

Additional notes:

  • When using fungicides, it is recommended to mix them with INTEGRA at a rate of 3ml per 20 liters of water. INTEGRA acts as a sticker, spreader, and penetrant, ensuring effective coverage.
  • Alternating the use of different fungicides throughout the crop season can help prevent the pathogen from developing resistance to any specific fungicide.
  • Providing proper nutrition to the plants can enhance their resistance to infections.

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