This project was undertaken to identify potential alternate hosts of tomato spotted wilt virus among the common weed species present within or adjacent to the lettuce crops and to assess the distribution of any potential virus reservoirs. It also monitored thrips populations entering the lettuce crops in order to determine the major species responsible for TSWV transmission and to determine the abundance of these vector thrips species at differing sites on affected farms over the cropping season. Finally, it correlated virus sources and thrips activity with disease incidence in the lettuce crop.