ABSTRACT
Plant pathogens are estimated to cause yield reductions of almost 20 percent in the principal food and cash crops worldwide (Oerke et al., 1994). Yield losses depend very much on climatic conditions and the susceptibility of the varieties grown, but crop rotation and other sanitation practices can also play a major role in reducing inoculum and delaying epidemic development. Fungicides are considered to be essential for the effective control of plant diseases in many crops, and today it is common practice to control diseases based on assessments of whether an attack of economic importance will develop.
