How to maintain oat health

Nitrogen affects disease incidence

Oats will be more susceptible to disease and pests where nitrogen and potassium availability are imbalanced. This imbalance can result in weaker crop growth, containing a higher concentration of soluble nitrogen compounds and carbohydrates. The latter provide a readily available food source for obligate parasite diseases such as the rusts, powdery and downy mildew. Excess nitrogen can increase disease incidence. With the facultative pathogens e.g. Altanaria and Fusariums, nitrogen will decrease disease incidence.

It is also important to maintain a balance between nitrogen forms present i.e. nitrate and ammonium as both of these have been identified at reducing specific plant diseases (nitrate reduces diseases from the Fusarium, Botrytis, Rhizoctonia and Pythium species, whilst ammonium has decreased severity of diseases from the Pyricularia, Gibberella and Sclerotium species).

Phosphate deficiency increases disease susceptibility

When phosphate is limiting, oat yield reduction and increased susceptibility to disease can occur. This response is again related to phosphorus deficiency restricted plant metabolism and growth leaving the developing plant prone to pathogen attack. Research has shown the increased incidence of mildew when phosphate is not applied by 50%.

Potassium deficiency or imbalance with nitrogen weakens plant disease resistance

Potassium deficient plants are poor at synthesising the products such as starch, proteins and cellulose giving rise to an accumulation of smaller compounds such as amides that are the food for diseases. Thinner cell walls with less mechanical resistance to predators may also result from potassium shortage. A review of over 1000 cereal trials found that where potash levels were low and out of balance with nitrogen supply, application of potash reduced disease and bacterial infections in over 70% of cases (PDA) in barley.

Potassium deficiency has also been linked to higher rates of rust infection and powdery mildew incidence.

Micronutrients influences plant disease infection 

Working with powdery mildew (Erysiphe graminis) Karl H. Schütte reported (Plant and Soil Volume 27) how the fungus spread rapidly over the boron deficient plants, less rapidly over copper, molybdenum and manganese deficient ones and slowly over the controls which received full-balanced mineral nutrition.

Manganese deficient plants more disease susceptible

Manganese has been associated with disease control in numerous investigations. It has a direct inhibitory effect on fungi growth, especially powdery mildew, as well as being involved in lignin and suberin production giving plant cells more physical resistance to infection. Manganese deficient plants have a poor ability to metabolise nitrogen giving an accumulation of nitrate nitrogen in the leaf. This acts as a food source for the diseases such as rusts and mildew, increasing the levels of infection in barley.

Zinc reduces sharp eyespot infection

Zinc has been shown to reduce the levels of infection of cereal blight / Sharp eyespot (Rhizoctonia cerealis).

Copper deficiency linked with ergot infection

Copper deficiency leads to male sterility giving blind grain sites that can become infected with ergot. Although ergot is rare in oats.