Sustainable Approaches to the Management of Soilborne Diseases in Nursery Production
Diseases caused by soilborne pathogens are a major limitation to field grown nursery production. The application of cover crops for soilborne disease management has not been widely investigated in woody ornamental nursery production system. Experiments were conducted to improve soilborne disease management efficiency through effective utilization of cover crops in nursery production and, to identify pathogens affecting ginkgo (Ginkgo biloba L.) and red maple (Acer rubrum L.) plants in nurseries of Tennessee and develop fungicide/biofungicide management recommendations for nursery producers. To determine the impact of cover crop in nursery production systems, soils from red maple production sites with and without cover crops [crimson clover (Trifolium incarnatum L.) or triticale (×Triticosecale W.)] were sampled following the senescence of the cover crops. Separate bioassays were performed using red maple cuttings on inoculated [with P. vexans, Phytophthora nicotianae (Breda de Haan) or Rhizoctonia solani (J.G. Kühn)] and non-inoculated field soils. The results indicated that winter cover crop usage was beneficial for inducing soil disease suppressiveness. There were lower disease severity and pathogen recovery with cover crops compared to the non-cover cropped soil. The rhizosphere pseudomonad microbial population was also greater when the cover crops were used. Similarly, the carbon and nitrogen (C:N) ratio of the soil was improved with the cover crop usage. Thus, in addition to improving soil structure and reducing erosion, cover crops can provide improved management of soilborne diseases. to identify pathogens affecting ginkgo (Ginkgo biloba L.) and red maple (Acer rubrum L.) plants in nurseries of Tennessee, morphological identification and sequence analysis of their internal transcribed spacer (ITS) regions, and large subunit (LSU) of the nuclear ribosomal RNA (rRNA), cytochrome c oxidase subunit I (Cox I) and cytochrome c oxidase subunit II (Cox II) of mitochondrial DNA (mtDNA) were done. Based on sequence results, Phytopythium vexans (de Bary) was described from the infected ginkgo and red maple plants. In addition, the efficacy of fungicides, biofungicides, fertilizer and host-plant defense inducers (traditionally recommended for management of oomycete diseases) for control of Phytopythium crown and root rot were evaluated on ginkgo and red maple ‘October Glory’ seedlings in greenhouse and field trials. Empress Intrinsic, Pageant Intrinsic, Segovis and Subdue MAXX fungicides were effective in both greenhouse and field trials, and the biofungicide Stargus reduced disease severity caused by pathogen P. vexans on ginkgo and red maple plants in greenhouse trials. These results will help nursery producers make proper management decisions for newly reported Phytopythium crown and root rot disease, and also Phytophthora and Rhizoctonia root rot of nursery crops.
"Sustainable Approaches to the Management of Soilborne Diseases in Nursery Production"
ETD Collection for Tennessee State University.