A BROADER CONCEPT FOR BIOLOGICAL CONTROL OF PLANT DISEASES
USDA ARS Appalachian Fruit Research Station, 45 Wiltshire Rd, Kearneysville, WV 25430, USA
Background and objectives
As we have gained more insight into the biological control of post-harvest diseases it became apparent that a broader definition of biological control was needed to encompass the complex interactions that occur. My objective is to define biological control of plant diseases in a manner that clearly distinguishes it from physical and chemical control, and that takes into account the multifaceted nature of biological control. The inclusiveness and exclusiveness of a definition affect relationships among the components of a definition and the subsequent evolution of scientific thought. For example, if genetic resistance is not considered biological control, scientists and concepts in biological control and genetic resistance will evolve independently.
Results and conclusions
I would like to present a definition of biological control which accounts for the unique nature of plant diseases and which encompasses all the elements of biological control that occur naturally. Therefore, I would like to define biological control of plant diseases as:
"The control of a plant disease with a natural biological process or the product of a natural biological process."
If we take this broad definition of biological control, chemicals extracted from living organisms would be 'biological', as well as those 'delivered' by living organisms. Also, host resistance (constitutive and elicited) would be biological control. Biological control under this definition would be clearly distinguishable from physical and synthetic chemical control of plant diseases.
Utilizing this broad definition of biological control we have pursued three avenues to control post-harvest diseases of fruits and vegetables biologically: (i) antagonistic microorganisms; (ii) natural plant- and animal-derived fungicides; and (iii) induced resistance . We have also combined these different types of biological control into a multifaceted biological control strategy . For example, when peaches are first subjected to LTV-C light to induce resistance, and subsequently treated with antagonistic yeasts, rot control is greater than the sum of the control by UV-C light and the antagonist alone .