Evaluation of select fungicides and fungicide programs for the management of late blight on tomato

摘要

Two trials were conducted in the same field at the Pennsylvania State University Russell E. Larson Agricultural Research and Extension Center in PA Furnace, PA on a Hagerstown silty clay loam. Plots were plowed on 22 May, and fertilizer (N-P-K, 46-0-0, 215 lb/A) was broadcast and incorporated. Tomato seedlings were transplanted on 25 Jun. A starter fertilizer 20-20-20 (N-P-K) along with Admire 2F (1.0 pt/A) was applied in the transplant water. Each plot was 12-ft long and separated by a 5-ft break within the row. Guard rows separated each treatment row. Each plot was planted with 8 transplants spaced 18-in. apart. Treatments were replicated four times and arranged in a randomized complete block design. Weeds were managed with an application of DualMagnum (1.5 pt/A) and Sencor DF (0.33 lb/A) on 21 Jun and supplemented with hand weeding. Plots were fertigated regularly (N-P-K, 20-20-20, 7 lb N/A) with a single line of drip irrigation tubing placed adjacent to the base of the plant. Fungicide applications were made using a tractor mounted, R&D CO2 powered side boom sprayer calibrated to deliver 28 gpa at 32 psi at the tank through one center and two drop TX-18 nozzles. All symptoms of late blight resulted from natural infection from adjacent guard rows artificially inoculated with a mix of three Pennsylvania Phytophthora infestans isolates of US23 (9.3 x 10~4 spores/ml sprayed in four locations per 12-ft of guard row) on 8 Aug. In the absence of rain, supplemental water was delivered using overheadmisters in the late afternoon for approx. 2 hr from 22 Aug to 6 Sep to extend the dew periods. Foliar late blight severity was evaluated on 24 and 30 Aug, and 3 and 8 Sep based on the percentage of the plot showing symptoms. Rainfall totals (in.) were 3.58, 5.17, 1.97, and 0.0 for 25 to 30 Jun, Jul, Aug and 1 to 8 Sep, respectively.