Landscape ecology as a new infrastructure for improved management of plantviruses and their insect vectors in agroecosystems

Pest and disease problems in agriculture frequently extend beyond the bound aries of an individual grower's fields, therefore management strategies in some pest and disease pathosystems may be more effectively addressed region ally. In the late 1980s, the tomato processing industry in the Del Fuerte V alley of Sinaloa, Mexico, became concerned about a complex of virus disease s affecting tomatoes. The principles of landscape ecology and the tools of geographic information systems were applied to help organize a cooperative regional approach to disease management of specific cropping systems. The m ajor tomato producers in the region provided skilled personnel to assess th e risk of virus disease incidence at the time of planting for specific fiel ds and to assess virus disease incidence later in the growing season. All d ata were spatially referenced using a geographic information system (GIS) a nd global positioning systems. Summary maps of perceived site risk and obse rved disease incidence for the region were made using geostatistics and GIS . Classical plant virus disease management strategies (avoidance or removal of sources of the viruses and their insect vectors, use of virus-free seed and transplants, etc.) were focused on areas of highest risk and incidence . The use of pesticides to manage the vectors of the virus pathogens was ac tively discouraged and greatly reduced. The incidence of tomato virus disea ses (representing as many as 10 possible viruses) in the Del Fuerte Valley peaked at an average of over 7% in 1991-1992 with disease incidence in indi vidual fields varying from 0% to 69% and dropped consistently each year to less than 1% in the 1995-1996 season with disease incidence in individual f ields varying from 0% to 11%. Geographic information systems and landscape ecology provided a regional perspective that was crucial in spatially refer encing, interpreting, and communicating information necessary to implement a regional disease management program. As geographic information system too ls become increasingly available, one of the challenges and opportunities w ill be the integration of agroecosystem data at the regional level to promo te the health of whole agroecosystems.