Evaluation of triazoles and other fungicides for control of gummy stem blighton watermelon, 2008

摘要

The experiment was done at the Clemson University Coastal Research and Education Center in Charleston, SC. The soil type was a Yonges loamy fine sand pH 6.2. The field was cropped to watermelon in fall 2007 and was fallow in spring 2008. Gummy stem blightwas present on watermelon in 2007 in this field. The field was disked three times prior to bedding. On 24 Jul 600 lb/A of 10-10-10 was broadcast within the row, and beds were cultivated lightly with a rotovator, shaped 1.5 ft wide on 6-ft centers, and covered with white-onblack polyethylene mulch. The herbicides Strategy 2.1EC and Sandea 75WG were applied at 6 pt/A and 1 oz/A, respectively, to the field on 29 Jul. Watermelon transplants were planted 2 ft apart into every other row on 31 Jul. The herbicide Dual Magnum was applied at 2 pt/A to the row middles with a shielded sprayer on 19 Aug. Cucumber beetles and pickle worms were controlled with Sniper 2EC at 6.4 fl oz/A on 19 Aug, 2 Sep, and 17 Sep and Spintor 2SC at 8 fl oz/A on 10 Sep. Quintec 2.09SC at 6 fl oz/A and Previcur Flex 6F at 0.6 pt/A were applied on 19 Aug, 2 Sep, and 17 Sep and Nova 40W and Tanos 50WDG were applied at 5 oz/A and 8 oz/A, respectively, on 10 Sep to prevent powdery mildew and downy mildew. Fulfill 50WDG was applied at 2.75 oz/A to manage aphids on 23 Sep. Drip fertigation with 8N-0P-8K plus minor elements was applied daily beginning 1 wk after transplanting. The N and K rates changed with growth stage: 1) 7 lb/week N and K from transplant to blossom, 2) 10.5 lb/week N and K from blossom to fruit set, 3) 14 lb/week N and K from fruit set to first harvest, and 4) 10.5 lb/week N and K after first harvest. The experimental design was a randomized complete block with 15 fungicide treatments and four replications. Plots wereone row wide and 30 ft long with 3 ft between plots within rows. Two plants between treatments within rows were inoculated with a conidial suspension of Didymella bryoniae (5 x 105 conidia per 0.03 fl oz) on 18 Aug. Leaf wetness was increased by using Senninger low pressure mini-wobbler sprinklers to produce a mist in the evening for 10 min at 7:00 and 11:00 p.m. from 18 Aug through the end of Sep. Fungicide treatments were applied with a CO2-backpack sprayer using a 36-in. boom with three TeeJet TX-26nozzles, orifice size 0.94 in., spaced 18 in. apart at 60 psi. The field was rated for percentage leaf surface area diseased with a modified Horsfall-Barratt 16-point scale weekly from 29 Aug through 6 Oct. Marketable fruit were harvested and weighed on2 and 8 Oct. Avg max/min temperatures for Jul, Aug, and Sep were 89.4/61.9, 88.1/64.2 and 83.9/59.6deg F., respectively.Rainfall for Jul, Aug, and Sep was 6.52, 6.11, and 5.77 in., respectively.