Submitted to: Fungicide and Nematocide Tests
Publication Type: Other
Publication Acceptance Date: 12/20/2002
Publication Date: 2/20/2003
Citation: PAULITZ, T.C., MCKINLEY, A., REINERTSEN, S. EVALUATION OF INFURROW APPLICATION OF QUADRIS AND ZINC FOR THE CONTROL OF RHIZOCTONIA ROOT ROT IN SPRING BARLEY. FUNGICIDE AND NEMATOCIDE TESTS. 2002. 581 CF007. Interpretive Summary:
Technical Abstract: An experiment was conducted on the McGregor Research Farm near Colfax, WA on a Thatuna silt loam, pH 5.8, 3.1% O.M. No-till plots had been direct seeded with spring wheat in 2001, winter wheat in 2000, and chemical fallowed in 1999. To increase disease pressure by Rhizoctonia, three green-bridge herbicide treatments were established: low disease pressure (Roundup Ultra [RU] applied on 8 Nov 01 at 1 quart/A); medium disease pressure (Roundup applied 3 wk before planting on 1 Apr 02) and high disease pressure (Roundup applied 3 days before planting on 18 Apr 02). All plots were planted on 20 Apr 02 with a Great Plains minimum-till drill, at 1.25 in. depth. The following treatments were applied in-furrow at the time of planting: control, Nitropak alone at 6 gal/A (13-3-0, McGregor Co.), Nitropak + Zn [Zn(NH4)2 EDTA,1 qt/A], and Nitropak + Quadris (2.08 lb a.i./gal) at 6.5 fl oz/A. Plot size was 7 X 70 ft. The experiment was arranged in a randomized complete block design, with three blocks, and all treatments (greenbridge and in-furrow application) were randomized within each block. Seedlings were harvested from the plots on 4 Jun 02, from three locations within each plot, five plants per location. Plant height, number of seminal roots and number of crown roots were counted on each plant. Roots were washed, digitally scanned to create TIF files, and analyzed with WinRhizo (Regents Instruments Inc, Québec, Canada) to determine root length, average root diameter, and number of root tips. These detailed root measurements provide quantification of Rhizoctonia damage, and have been correlated with Rhizoctonia induced root disease in greenhouse tests. Roots were also plated onto a semiselective medium (water agar + 1 ppm benomyl + 100 ppm chloramphenicol), to determine the percentage of roots infected with either species. Soils containing roots from these locations were assayed for the presence of Rhizoctonia spp. using a toothpick baiting technique. The timing of Roundup application had a significant effect on all measured parameters, with the lowest yields and plant measurements in the plots treated with Roundup 3 days before planting. In these treatments, Rhizoctonia spp. could bridge from the dying weeds and volunteers into the planted barley. Both R. oryzae and R. solani AG-8 were recovered from the experimental plots, with R. oryzae being predominant. However, due to large variation within plots, there was no effect of treatments on the percentage of roots colonized by Rhizoctonia spp. or on the frequency of recovery from the soil with the toothpick assay. In the 3-day Roundup treatments, Quadris significantly increased barley yields, but no significant increase in yield was measured for the 3 wk RU treatment. Quadris application significantly increased the number of crown roots in the 3-wk Roundup treatments (P?0.10). The number of root tips and the average root diameter were also affected by Quadris in the 3-day and fall Roundup treatments, respectively. Zn had no significant effect on yield or other plant measurements.