Crop diseases are as old as agriculture itself and there are many examples in history where people have suffered as a consequence of plant diseases. For example, the Romans used to sacrifice a red dog every year to appease the rust goddess Rubiga. Blight of potato caused the Great Famine in Ireland. More recently, Ascochyta blight decimated Wimmera chickpea crops in the late 1990s and brought hardship to many farmers.
Diseases cause economic losses to crops by attacking the plant at many different places and stages in its growing cycle. Some will cause damage by interfering with water and mineral absorption from the soil (diseases of the roots and stem base), some will affect photosynthesis by killing the leaves of the plant (diseases of the foliage), some will impair translocation of sugars produced in the photosynthesis to the grain (systemic virus diseases) and yet others will completely destroy developing grains (disease of the head and kernel).
Diseases remain a constraint to field crop production. They are estimated to causes annual losses valued at around $120 million for Victoria. Without on-going, current control practices this loss could be much higher.
This manual will outline the general principles of plant pathology, the conditions that favour disease development, how to scout for diseases and how to control them. More specific diagnostics and control aspects for cereal, pulse and canola diseases will be covered in following chapters.
Introduction to Crop Diseases
What is a Disease?