Ergot (claviceps purpurea) affects many cereals and grasses. Rye and triticale are more susceptible than wheat and barley.
Cool damp weather in late spring and early summer favours ergot germination as well as prolonging the flowering period of cereals and grasses thus increasing the risk of infection.
Ergot is more of a problem when florets stay open for a lengthy time. This may be an effect of variety but may also be due to poor nutrition of the crop. Nutrients, which can affect ear fertility, include Boron and Copper, both of these elements are becoming more deficient in soils as they are removed by crops or by leaching and not replaced.
Research in Canada, Australia and Kenya has shown that copper deficient cereals are more susceptible to ergot. Work in the US and Canada has shown that the presence of Ergot is strongly correlated with soils which are low in copper, or with management practices that cause copper deficiencies.
Copper deficiency is associated with low protein levels in cereals and ripening may be delayed. Genotypes with high protein concentrations in the grain have been shown to respond more sensitively to copper deficiency than genotypes with low grain protein concentrations (Nambiar 1976)
Copper is also implicated in the production of polyphenol oxidases, which are involved in the balance of phytohormones, the lignification of cells and in defence responses to viral and fungal infection.
Copper deficient plants have thin cell walls with little lignin thus making entry of disease easier. Copper deficient plants have been shown to be more susceptible to Take-all, mildew and possibly septoria.
The formation of flowers and fruit may be more seriously affected than growth since the synthesis of compounds needed for these organs is inhibited at an early stage. Pollen may become sterile and ovaries may be reduced in size.
High phosphate levels inhibit uptake of copper if soils are low. Heavy dressings of potash, high pH soils and high humus levels all reduce uptake High N levels delay the translocation of copper from older leaves to the growing point i.e. the ear thus enhancing copper deficiency.
HGCA reported that 5% of land in England and Wales and 30% of land in Scotland was deficient in Copper. Results from soil analyses suggest that these figures are now much higher.
Copper deficiencies can also result in later maturity of the crop.
Boron applications have also been shown to reduce the incidence of ergot in barley. Boron is known to affect the number of flowers produced, the retention of flowers, pollen germination, pollen tube growth and seed and fruit development. For normal growth and maturity there must be a steady supply of boron to the meristems. Anything that interrupts this steady supply will cause a malfunction of the meristem Low or deficient levels of boron may cause flowers to fail to pollinate by inhibiting anthesis thus exposing them to ergot spores. Since boron is poorly translocated within the plant a continuous supply or repeated applications gives best results.
Boron can leach from soils, particularly when rainfall is heavy! And research has shown that as levels of N and K fertilisers are increased more boron is required. Although cereals are regarded as not requiring boron, they can remove as much boron per acre as 20t/acre crop of cabbages.
Wet growing conditions induce shallow rooting in the topsoil layers €“ this is where copper and boron are most deficient.Any herbicides/growth regulators, which affect rooting, may also affect nutrient uptake.
Research in Canada has shown that applying Cu to the soil can reduce levels of ergot.
Plants generally respond best when nutrients are available throughout the growing season, the best way to achieve this constant availability is by applying granular B and Cu to the soil. This also eliminates the risk of scorching the growing crop.
Copper oxysulphate granules (15%Cu,) and boron granules (10% B) may be broadcast on the soil at rates of 5-10kg for B and 10-20kg/ha for Cu(depending on soil levels) in autumn in order to start correcting the soil deficiency.
Otherwise where copper is known to be low apply a spray as soon as conditions allow. Further applications at the late tillering stage and early boot are likely to benefit the crop. Applications after the early boot stage can be detrimental.
Where B is deficient apply B at these growth stages