Evaluation of Cornell late blight Decision Support System for timing fungicide applications for foliar diseases in tomato, NY, 2014

摘要

The goal of this experiment was to evaluate the Cornell Decision Support System (DSS) for naturally-occurring late blight on organically-grown tomato using an organic copper fungicide (Nordox 75WG) applied to a susceptible cultivar (Mountain Fresh Plus) and a moderately resistant cultivar with the Ph2 gene for resistance to late blight (Legend). The experiment was conducted at the Long Island Horticultural Research and Extension Center in Riverhead, NY, in a field with Haven loam soil that has been dedicated to organic research since 2001. A combination of Pro-Grow, Cheep Cheep, and Cotton seed blend fertilizers was spread at 700 lb/A (105 lb/A total N) over rows to be planted, then incorporated on 28 Apr. Drip irrigation tape was laid as the rows were covered with black plastic mulch. A living mulch of annual ryegrass was planted between rows by broadcasting seed with a hand-operated spreader, then lightly raking to incorporate on 6 May. The ryegrass plus weeds that grew were mowed routinely. Someweeds were removed by hand. Tomato seed were sown in an organic seeding mix in the greenhouse on 6 May. Seedlings were transplanted by hand on 9 into holes pre-made by a waterwheel transplanter that also applied starter fertilizer, Neptune's Harvest Benefits of Fish (24-1 N-P-K). Additional drench applications of this fertilizer to the base of plants were made on 8, 15, and 29 Aug, and 5 and 12 Sep. A completely randomized block design with four replications was used. Plots consisted of 10 plants in asingle row with 24-in. plant spacing and 68-in. row spacing. Plots for each of the four replications were in two adjacent rows. Plants were staked and trellised using a Florida weave trellising system with 4-ft stakes according to standard commercial practices. Water was provided as needed through drip tape. Insect pests were managed by applying Entrust (8 oz/A) on 17 Jul, 25 Jul, 4 Aug, and 2 Sep. Treatment applications to foliage were made using a CO2-pressurized backpack sprayer with a boom that hasa single twin-jet nozzle (TJ60-11004VS), calibrated to deliver 50 gal/A when operated at 54 psi and 2.4 mph. Each side of the planted row was treated with the boom held sideways to obtain thorough coverage of foliage and to mimic the coverage obtained with a drop nozzle on a tractor sprayer. A preventive 7-day application schedule was the standard program. A total of 14 applications were made from 22 Jun through 24 Sep. Timing of applications made following the DSS (http://blight.eas.cornell.edu/blight/) were adjusted as needed to avoid weekend days. Leaves were examined for symptoms of any foliar disease twelve times from 16 Jul to 29 Sep. Late blight and other diseases observed were assessed by estimating the percentage of leaves in each plot with symptoms (incidence) and the severity of symptoms on these affected leaves. Canopy severity was calculated by multiplying these values. Area Under Disease Progress Curve (AUDPC) was calculated for late blight severity from 26 Aug through 29 Sep for all entries. Average monthly high and low temperatures (°F) were 79/60 in Jun, 82/67 in Jul, 81/64 in Aug, 77/61 in Sep, and 66/53 in Oct. Rainfall (inches) was 2.47, 2.24, 2.42, 1.86, and 5.43 for these months, respectively.