Using host resistance and reduced risk fungicides to control early blight and Septoria leaf spot on tomato, 2008

摘要

Tomato seedlings of an early blight tolerant and susceptible hybrid, NC06115 and Supersonic, respectively, were transplanted on 5 Jun into a Howard gravelly loam at the H. C. Thompson Research Farm, Freeville, NY. Two identical but separate plantingswereestablished, one for the early blight (EB) experiment and another for the Septoria leaf spot (SLS) experiment. The four fungicide treatments and unsprayed control were arranged in a split-plot design with the two varieties nested within each block and replicated fourtimes. Each block consisted of one row for each variety, with each containing eight plants spaced 22 in. apart within a 15 ft row. There were 3 ft between the varieties and 10 ft between blocks. On 11 Jul, one plot area was inoculated with 50,000 spores/ml of our isolate 10 of A. tomatophila while the other area 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 4.00, 5.43, 3.59, and 2.45 for Jun, Jul, Aug, and Sep, respectively. 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. All sprays were appliedon a 7-day schedule (14, 25, 30 Jul; 6, 13, 20, 27 Aug). Serenade MAX + Actigard 50WG were applied with the backpack sprayer on 2 and 9 Jul (presprays), prior to the regular fungicide program. Defoliation was assessed using the Horsfall-Barratt rating scale (0-11) on 21, 31 Jul; 9, 14, 21, and 28 Aug. Foliar data were transformed using the area under the disease progress curve (AUDPC) equation to account for foliar disease, which increased over time. Stem ratings were taken on 28 Aug using a 0-5 scale, with 5 being the most severe. Data were analyzed using Proc Mix with SAS and significant differences between means were separated using the Tukey-Kramer test at alpha=0.05.