Control of late blight on tomato in western Washington using high tunnels
D. Inglis (1), B. GUNDERSEN (2)
(1) Washington State University, Mount Vernon, WA, U.S.A.; (2) WSU Mount Vernon NWREC, Mount Vernon, WA, U.S.A.
Control of late blight (LB) using high tunnels (HT) was studied near Mount Vernon, 2008 to 2010, by comparing HT vs. open field (OF) grown tomatoes, exposed to natural inoculum of Phytophthora infestans. Six-wk-old seedlings of five susceptible (Big Beef, Early Girl, Northern Delight, Oregon Spring, Stupice) and one resistant (Legend) cultivar were transplanted into one or two blocks of HT and OF plots on 6/03/08 or 6/02/09 using four reps of six plants per cultivar. In 2010 four blocks with four reps each of Early Girl, Oregon Spring and Stupice seedlings were transplanted 5/27/10 or 6/3/10 into HT or OF. Plants were drip-irrigated, staked and pruned, and rated weekly for disease. Environmental data were recorded every 15 min. Low LB pressure precluded differentiation between HT and OF plots in 2009. However in 2008, the range of area under disease progress curve (AUDPC) values across cultivars was lower in the HT (0 to <1) vs. OF (71 to 246) blocks. Similarly in 2010, average AUDPC values and percent blighted fruit were significantly (P = 0.001) less in the HT (<1 and 1.1%) vs. OF (344 and 13.2%) blocks. LB disease severity values (dsv) calculated by WISDOM software (UW-IPM) were also lower, number of days to 18 dsv longer, and total hr of leaf wetness less for HT compared to OF all three years. In both 2008 and 2010, fruit yield was higher or significantly higher in HT than OF indicating HT as a desirable tomato cropping system for managing LB in the region.
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