Using host resistance and reduced risk fungicides to control early blight, Septoria leaf spot, and late blight on tomato, 2009.

摘要

Tomato seedlings of susceptible Mountain Fresh Plus and other tomato genotypes differing genetically in their reaction for early blight (EB), Septoria leaf spot (SLS) and late blight (LB) were transplanted on 2 Jun into a Howard gravelly loam at the H. C. Thompson Research Farm, Freeville, NY. Two identical but separate plantings were established, one for the EB experiment and another for the SLS experiment. The four fungicide treatments and unsprayed control were arranged in a split-plot design withthe four tomato genotypes nested within each block and replicated four times. Each block consisted of one row for each variety, hybrid or line, with each containing eight plants spaced 22 in. apart within a 15 ft row. There were 3 ft between the genotypes and 10 ft between blocks. On 11 Jul, one plot was inoculated with 50,000 spores/ml of isolate 10 of A. tomatophila, while the other was inoculated with 1 x 106 spores/ml of S. lycopersici. Both pathogens were applied to each plant with a backpack sprayer to the point of run-off, approximately 60 ml/plant. Rainfall (in.) was 4.81, 4.00, 5.83, and 2.37 for Jun, Jul, Aug, and Sep, respectively, for a total of 17.01 in., with no additional irrigation required. LB occurred in both plots from natural outside air-borne inoculum. To allow the continuation of ratings in both the EB and SLS plots, three additional fungicide sprays were applied to reduce the spread of LB in the susceptible genotypes; Revus 250SC at 8 fl oz was applied on 26 Aug and Curzate 60DF at 5 oz on 21 Aug and 2 Sep. All fungicides were applied with a CO2 pressurized boom sprayer at 60 psi, delivering 23 gal/A through eight TeeJet XR11003 flat fan nozzles spaced 20 in. apart. The fungicide spray programs consisted of the same products in both experiments, but the application timing varied slightly. Our weekly conventional grower treatment, Bravo Weather Stik (WS) 6SC, was compared with the weekly organic treatment, Serenade MAX WPB combined with Nu-Cop 3L or with Nu-Cop 3L used alone.Additional fungicides were applied in two treatments following the Tom-Cast program, using 18 or 25 DSV to trigger applications with the reduce-risk fungicides Quadris Top 325SC applied three times with a single Endura 70WG spray used after the second Quadris Top spray. The 7-day spray schedule for EB was applied 8 times (22, 29 Jul; 4, 11, 18, 25 Aug; 1, 8 Sep), while the weekly program for SLS was applied 7 times (29 Jul; 4, 11, 18, 25 Aug; 1, 8 Sep). The 18 and 25 DSV treatments required 4 sprays. Foliar defoliation was assessed for EB, SLS and LB using the Horsfall-Barratt rating scale (0-11) and stem ratings for EB and SLS using a 0-5 scale, with 5 being the most severe, on 7, 14, 21, 28 Aug; 1, 10 Sep. Data were converted to area under the disease progress curve (AUDPC) to account for disease increase over time. Data were analyzed using Proc Mix with SAS and significant differences between means were separated using the Tukey-Kramer test at alpha=0.05.