High Tunnel and Grafting Effects on Organic Tomato Plant Disease Severity and Root-knot Nematode Infestation in a Subtropical Climate with Sandy Soils

Abstract

The U.S. fresh-market tomato industry faces increasing competition from Mexico, which achieves greater productivity and quality due to the use of protected structures. Protected agriculture is limited in humid, subtropical regions of the United States. Although grower interest in high tunnel production has increased in recent years, systematic high tunnel research has not yet been conducted in subtropical Florida. Additionally, although tomato grafting has shown the potential to overcome biotic and abiotic stresses, research of high-tunnel, grafted tomato production in subtropical conditions is lacking. During this 2-year study (Citra, FL), a side-by-side comparison of open field and high tunnel organic tomato production was conducted using a split-split plot design. The most significant benefit of high tunnel production was season extension achieved through the reduction of foliar disease severity, which reduced the area under the disease progress curve by 64% across two seasons. This may be largely attributed to the pronounced reduction in the duration of leaf wetness during the wet months of the growing cycle. Grafting with ‘Multifort’ rootstock reduced the root-knot nematode soil population density by 88% as well as root galling severity, both of which demonstrated the potential for increased levels in the high tunnel production system compared with open field production. The more severe root-knot nematode infestation in high tunnels was likely due to the modification of soil temperatures, which were 2 °C greater during the early part of the season but were reduced after shadecloth application. Compared with the open field, solar radiation was reduced by 23% in the high tunnel before shadecloth application and by 51% after shadecloth application; however, due to the high radiation levels in subtropical Florida, daily light integral levels indicated that light was not limiting for high-quality tomato production. The average wind speed was reduced by 57% in the high tunnel and, together with the reduction in solar radiation, indicated the potential reduction in summer abiotic stress and evapotranspiration within high tunnels. These results revealed that the integrated use of high tunnel and grafting technologies may be important for enhancing fresh-market tomato production in the humid subtropics, especially in organic systems.