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Disease management can increase productivity, quality of forage crops

by Wyoming Livestock Roundup

Farmers and ranchers alike depend on forages to support their lifestyles and feed their animals, but understanding and managing forage diseases provides multiple benefits for producers, according to Linda Jewell of Agriculture Agri-Food Canada (AAFC).

On Dec. 12, in a webinar titled, “Understanding and managing forage diseases,” hosted by Beef Cattle Research Council, Jewell, a plant pathology research scientist, discussed ways producers can better understand forage diseases.

Jewell also offered a look into what forage diseases are, how to identify them and what causes plant diseases.

Disease basics

A plant that can carry out normal physiological functions, like photosynthesis, to their best potential is considered a healthy plant, noted Jewell.

“Diseases disrupt the normal physiological functions of a plant and are be separated into two categories, abiotic or biotic diseases,” she explained.

Non-living organisms or factors, like nutrient deficiency or weather, cause abiotic diseases, added Jewell, while biotic diseases are caused by bacteria, fungi or viruses.

“Insects can cause plant damage and are sometimes an important factor in managing diseases because they spread diseases from field to field,” she added.

To determine if a plant has a disease, producers should look for signs and symptoms, which vary depending on the type of disease.

“A symptom is the result of a disease, such as yellowing leaves or wilting,” Jewell stated. “Signs of a plant diseases are observations of the disease cause, like the presence of fungi or bacteria.”

She mentioned knowing the signs and symptoms of any particular diseases helps producers identify diseases and determine what steps should be taken to reduce impacts of forage diseases.


Fungi, bacteria and sometimes viruses, Jewell stated, are the main sources of plant diseases.

“A majority of plant diseases are caused by fungi, which grow tiny hair-like structures called hyphae that tangle together and form a mycelium. The mycelium is what producers see on the plants,” said Jewell.

She mentioned most fungi also produce spores, or seeds, that are spread by wind and water.

“Fungi can survive in unfavorable conditions like cool weather by living in dead plant tissues or other live plants near fields. Fungi also create sclerotia, a hard and dark-colored survival structure made of mycelium, which is very resistant to extreme temperatures and moisture,” Jewell explained.

Another type of plant disease, often known as water mold, are oomycetes, she added.

“Oomycetes spores can move around in water, and if there is consistent moisture in the soil, the spores will find other plants to attack,” she noted.

Common diseases

There are a few plant diseases very commonly found in forages that don’t usually cause significant damage or economic loss, Jewell mentioned, adding some diseases, left unmanaged, can cause yield loss and plant death.

“Rust is a very common disease in all types of forages,” she said. “Rust is a spore producing fungus, so the wind can carry the disease from one field to another. Typically, producers will see bright orange, powdery spots on plant leaves and stems.”

Ergot is a forage disease producers should be aware of because the fungus produces a toxin that could be dangerous to animals if too much is eaten.

“The toxin produced by ergot causes severe blood vessel restriction and can cause abortion in livestock,” Jewell explained.

Simply put, not all plant diseases are dangerous, but producers need to pay close attention and manage plant diseases before they get out of hand to prevent economic losses, she mentioned.

Management strategies

According to Jewell, managing forage diseases is necessary for the success of farmers and ranchers who rely on their crops.

“Plant diseases reduce nutrition quality, stunt plant growth and can potentially harm livestock,” she explained.

Plant pathologists use disease triangles as a management tool for plant diseases to look at the factors that determine disease severity, Jewell stated.

The disease triangle consists of three factors, including the host, pathogen and environment.

“All three factors play an important role in affecting the amount of disease present in an area,” mentioned Jewell, adding, “If the host is susceptible and the pathogen is strong but the environment is unsuitable, the disease won’t spread much.”

Variety selection

Selecting the appropriate forage variety is also a tool producers can use to reduce the risk of damage from diseases.

“It’s really important for producers to pick the right variety of forage based on the area and specific purpose of the crop,” said Jewell. “Selecting the right variety for specific diseases in the area is also important for producers to consider.”

Another disease management tool is crop rotation because fungal spores and sclerotia can persist in the soil and cause problems for the same crop next year.

“Rotating different crops, when possible, gives pathogens in the soil time to diminish,” Jewell stated.

Applying excess fertilizer can be a major problem for producers trying to manage plant diseases for many reasons, according to Jewell.

“If producers apply fertilizer when plant growth should be slowing down, then plants are more likely to be damaged by abiotic factors like cold weather,” she mentioned. “Pathogens can also benefit from the application of fertilizer making the disease harder to manage.”

Reducing or minimizing leaf and soil moisture can also be helpful in preventing the spread of plant diseases, Jewell noted.

“Moisture that persists in the soil or on the leaves invites diseases to take hold,” she added.

Implementing disease management strategies helps producers decrease the risk or amount of crop damage caused by plant diseases, which is beneficial for their operations.

Heather Loraas is assistant editor of the Wyoming Livestock Roundup and can be reached at

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