Brown rust of lyme grass

The biological cycle of the pathogen involves the formation of various spore types, enabling both intensive vegetative reproduction and successful overwintering under adverse conditions.

The fungus primarily infects members of the Leymus genus, commonly known as lyme grass. The pathogen penetrates the plant epidermis through stomata, then develops mycelium within the tissues, actively absorbing nutrients.

During its cycle, the fungus produces uredinia and telia, which is characteristic of many rust fungi. Pathogen spores are highly volatile and can be carried by air currents over long distances.

The genetic plasticity of Puccinia elymi allows it to adapt to various ecological and geographical zones where its host crop is cultivated.

The first visual sign of lyme grass infection is the appearance of characteristic small yellowish-brown pustules (uredinia) on the leaf and stem surfaces.

As the disease progresses, the spots become more pronounced and take on a brown or rusty hue, visually resembling iron oxidation.

Heavy infection leads to mass rupturing of the epidermis, through which masses of fungal spore powder emerge.

As the disease advances, affected leaves turn yellow prematurely, curl up, and gradually die, significantly reducing the plant's overall photosynthetic surface area.

• Appearance of rusty spots on leaf blades.
• Powdery spore deposits on infected areas.
• Yellowing and premature drying of vegetative organs.

The development of brown rust in lyme grass directly depends on weather conditions, particularly high air humidity during the grass's active growth period.

The temperature optimum for urediniospore germination ranges from +15 to +22 degrees Celsius, making the disease most dangerous during cool and wet periods.

Frequent dew, fog, and prolonged rainfall facilitate the rapid spread of infection within crops, as moisture is essential for effective spore germination.

Dense stands and areas with poor aeration create a favorable microclimate for moisture accumulation and retention, which triggers disease outbreaks.

Excessive nitrogen fertilization, which leads to overdevelopment of vegetative mass, often weakens plant immunity and makes them more susceptible to the pathogen.

The primary danger of brown rust is a sharp decline in the nutritional value of lyme grass used as a pasture crop.

As a result of tissue damage, the photosynthesis process is disrupted, leading to a significant loss of green mass and hay compared to healthy crops.

Plants infected by the pathogen become less resistant to other adverse environmental factors, including drought or winter frost.

Long-term fungal influence leads to the inhibition of tillering processes and weakening of the root system, which negatively affects the productive lifespan of the grass stand.

In cases of epiphytotic disease development, yield losses can be substantial, making lyme grass cultivation on infected plots economically unviable.

To prevent the spread of the disease, it is necessary to follow proper agronomic standards, including optimal seeding density to ensure adequate ventilation.

A crucial practice is the timely harvesting of green mass, which prevents the accumulation of inoculum on overgrown grass.

Breeding and the use of rust-resistant lyme grass varieties remain the most effective and economically sound method of crop protection.

The application of chemical fungicides is justified only on seed plots upon the first signs of disease, in accordance with pesticide application regulations.

Sanitary measures aimed at destroying plant debris help to reduce the infection load in the fields for subsequent seasons.