Control of powdery mildew and leaf rust in irrigated hard red winter wheat in Oklahoma, 2008

摘要

A field trial was conducted to determine the efficacy of fungicides to control powdery mildew and leaf rust in irrigated hard red winter wheat. The trial was conducted in north central Oklahoma near Stillwater in a Norge loam soil. Pre-plant fertilizer (100 lb/A of 18- 46-0) was applied on 28 Aug. Eraser (1oz/gal) was used pre-planting to spot treat emerging grassy weeds. Seeds of the cultivar Jagger treated with Gaucho 480F (3 fl oz/cwt) were planted on 31 Oct 2007 at a rate of 60 lb/A. Plots were 20 ft long and 4 ft wide with 7 rows. Approximately 0.20 in. of water by sprinkle irrigation was provided on 30 Apr and on 1, 3, 5, 13 and 15 May to facilitate disease development. Other management practices were applied according to Oklahoma CooperativeExtension guidelines. Treatments werereplicated four times in a randomized complete block design. Fungicides were applied in water (20 GPA) on 25 Mar [Feekes’ growth stage (GS) 7], 7 Apr (GS 8), and 22 Apr (GS 10.2) using a CO2 wheelbarrow sprayer with flat fan nozzles (8003EVS) spaced 18inches apart. Powdery mildew was first observed in mid-April, and the second leaf below the flag leaf (F2 leaves) and lower were rated for severity on 30 Apr and 8 May. Leaf rust was first observed in mid-April, and severity ratings were taken on flag leaves on 8, 16 and 21 May. Plants were rated for powdery mildew and leaf rust severity based on the percent leaf surface area infection on a scale of 0-99% (modified Cobb’s scale). The trial was harvested on 5 Jun using a Hege small-plot harvester, and yield (bu/A) and test weight (lb/bu) were determined for each treatment. Results were analyzed using the PROC GLM ANOVA of SAS, and means were separated by Fisher’s Least Significance Difference (FLSD) test at P<=0.05.