Evaluation of fungicide programs for control of foliar diseases and stem rot on Spanish-type peanuts, trial 1, 2018

摘要

The trial was conducted at the Caddo Research Station near Ft. Cobb, OK in a field containing a Binger fine sandy loam soil previously cropped to peanuts. Granular fertilizer 18-46-0 lb/A N-P-K was applied prior to planting on 8 May using strip-till techniques. The herbicides Prowl H2O 3.8F at 2 pt/A and Valor 51WDG at 2 oz/A were applied pre-emergence after planting. Post-emergence herbicide applications included Helmquat 3SL at 8 fl oz/A + Dual Magnum 7.6E at 1.3 pt/A on 15 May, Helmquat 3SL at 8 fl oz/A on 4 Jun, Clethodim 2E at 1 pt/A on 18 Jun, Cobra 2E at 12 fl oz/A + Basagran 4L at 2 pt/A + Butyrac 200 at 1 pt/A on 18 Jun, and Clethodim 2E at 1 pt/A on 7 Jul. Plots consisted of four 25-ft-long rows spaced 36 in. apart. The experimental designwas a randomized complete block with four replications separated by a 5-ft-wide fallow buffer. All data were taken from the two center rows. Fungicides were applied broadcast through flat-fan nozzles (8002vk) spaced 18 in. apart with a CO2-pressurized wheelbarrow sprayer. The sprayer was calibrated to deliver 21 gal/A at 40 psi. Treatments received five applications on ca. 14-d intervals beginning 5 Jul. Plots were inoculated with S. rolfsii by sprinkling millet seed colonized by the fungus along the center two rows of each plot at 50 ml/plot on 15 Aug. Rainfall during the cropping period (May through Oct) totaled 3.5 in. for May, 3.75 in. for Jun, 4.03 in. for Jul, 1.61 in. for Aug, 7.31 in. for Sep, and 6.02 in. for Oct. Plots received 16 applications of sprinkler irrigation at 0.5 to 1 in. per application that totaled 10.5 in. of water. Leaf spot and web blotch were assessed by estimating the percentage of leaflets with symptoms (including defoliated leaflets) and the percentage of leaflets defoliated in three areas per plot on 10 Sep and 16 Oct. The incidence of web blotch was evaluated separately on 10 Sep but not on 16 Oct when only total foliar disease could be assessed. Stem rot was assessed by counting the number of 6-in. row segments withsymptoms on 10 Sep and 16 Oct. The counts were converted to the percentage of row length affected. Plots were dug and inverted on 22 Oct, windrowed for 7 d, and harvested with a combine equipped with a sacker. Pods were dried and cleaned prior to weighing. Data were analyzed using the GLIMMIX procedure of SAS 9.4 and means were separated by the LINES option, which produces a LSD-type of multiple comparison, where indicated by a significant (P<0.05) treatment effect.