Agricultural Research Western Australia, Locked Bag No. 4, Bentley Delivery Centre, Bentley, Perth, WA 6983, Australia.
The importance of dissecting out the ways in which diverse types control measures against plant viruses operate before taking decisions on which to use will be emphasised. An increasingly sophisticated range of control measures are becoming available to meet the challenge that virus epidemics pose to achieving satisfactory yields and quality of plant produce. Some are entirely non-selective affecting a wide range of viral pathogens or their vectors, but others are selective targeting a particular virus or vector species. Control measures also differ in activity by targeting either the initial source of inoculum, which may be external or internal, or the rate of virus spread, which may be influenced at early or late stages of the epidemic. In general, cultural (phytosanitary and agronomic) and legislative measures are non-selective, whereas host resistance and most biological control measures are. Chemical control measures have low selectivity when a general pesticide is applied but high selectivity when a selective pesticide is used. A drawback to selective measures is that their use may result in selection of variants of virus or vector that are more difficult to control. Host resistance, chemical and biological control measures decrease the rate of virus spread but are inactive against the initial virus source whereas legislative and phytosanitary control measures and many agronomic measures address both source and spread. When combining control measures within integrated disease management, success is optimized by including measures that are selective and others that are non-selective, and that address both kinds of sources and phases of virus spread.
