Researchers have been trying to find correlations between mineral nutrients and pest and disease management. Summaries of their finding all point in the one direction: plants with optimal nutritional status have the highest resistance to diseases and that susceptibility increases as nutritional status deviate from this optimum5 .
Nutrition, although frequently unrecognised, always has been a primary component of disease control and management1 . Early settlers moved onto fresh soils and as readily available nutrients were depleted, disease severity increased. Crop rotation and fallowing practises made crop production possible by increasing the supply of readily available nutrients and controlling weeds which competed for nutrients and water. Nutrition of the plant can be drastically altered by many pathogens and it is frequently difficult to clearly differentiate between biotic and abiotic factors which interact to “cause” a nutrient deficiency or excess.
All of the essential mineral elements are reported to influence disease incidence or severity2,3,4 . The effect of mineral nutrients on disease has been determined by three factors. These are through observing the effect of fertilisation on disease severity, comparing mineral concentrations in resistant and susceptible cultivars or tissues and through correlating conditions influencing mineral availability with disease incidence or severity and a combination of all three.