Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange
Abstract
Control of Phomopsis blight (P. juniperovora) of eastern redcedar (Juniperus virginiana) with benomyl was investigated using potted seedlings in a greenhouse. Benomyl sprays and drenches did not prevent infection. However, three pre-inoculation foliar sprays (600 ppm a.i.) applied at weekly intervals followed by three post-inoculation sprays gave significant control of disease progression. Benomyl drenches of 0, 6.5, 13, 40, 80, 160, 320 and 640 mg/liter pot resulted in significant blight control with the 40 to 640 mg treatments. Thin layer chromatography coupled with Penicillium bioassay determined that 3 μg of benomyl (MBC)/g plant tissue (fresh weight) was the minimal concentration necessary to limit disease progression. Fungitoxic activity was also determined biweekly in nursery grown 2-0 eastern redcedar receiving benomyl applications of 0.6 kg/ha biweekly, 1.4 kg/ha monthly, or 2.8 kg/ha every 6 weeks. Analysis for systemically transported benomyl (MBC) revealed concentrations to be less than the minimal amount necessary for disease control as indicated by the greenhouse experiments. However, the percentage of trees with pycnidia and the percentage of pycnidia with spores were both significantly lower in the benomyl treatments
