Techniques Involved in Greenhouse Evaluation of Deciduous Tree Fruit Fungicides

Fungicides play a major role in modern agriculture in helping to assure production of crops threatened by fungus diseases when other practical and economical measures are lacking. Although a fungicide literally is a chemi­ cal that kills the fungus spores or mycelium, this paper deals with a broader definition to include fungus inactivation and suppression to prevent or restrict harm to plants (4, 10). Activity of fungicides reflects a combination of complex modes of action, both biochemical and physical. Our knowledge of biochemical modes of fungicidal action is still too meager to aid greatly in the discovery of new effective fungicides for agriculture. Chemical and pharmaceutical industries are the only source of agricul­ tural fungicides. Many companies rely on a hit-or-miss screening of thou­ sands of chemicals for chance discovery of a new family of fungitoxic ones. Some companies exhaustively research families of known promising fungi­ cides. Usually after some research with these on selected plant pathogenic fungi on selected test plants for control efficacy, effective dosage, phytotox­ icity, and also toxicology and with considerations of patent rights, market