Abstract
Soilborne pathogens are a significant economic problem for nursery production in the Southeastern United States. The goal of this study was to determine the impact of cover crops on soilborne disease suppressiveness in such systems. Soils from red maple (Acer rubrum L.) plantation fields grown with and without cover crops were sampled, either while the cover crops were growing (pre-disked) or post-season, following cover crop incorporation into the soil (post-disked). Greenhouse bioassays were conducted using red maple seeds on inoculated (with Rhizoctonia solani (J.G. Kühn) or Phytophthora nicotianae (Breda de Haan)) and non-inoculated field soils. The damping-off, root rot disease severity, percent recovery of Rhizoctonia and Phytophthora, and pseudomonad population were examined during the two years of the experiment. Results showed that cover crop incorporation was beneficial for inducing disease supressiveness characteristics of soil. Cover crop incorporation into the soil significantly or numerically reduced disease severity and pathogen recovery in infested soil compared to the bare soil treatment. Cover crop incorporation was found to be partially associated with the reduction of seedling damping-off. The pseudomonad microbial population was greater when cover crop was present, and is thought to be antagonist to soilborne pathogens. Therefore, cover crops can be integrated in field nursery production systems to suppress soilborne pathogens.
Highlights
Ornamental nursery production is a lucrative segment of the green industry
Cover crops are known to prevent soil erosion [39,40] and effect weed suppression [41,42], and are capable of changing soil microbial populations [14]. These characteristics are often related to increased soil fertility in agricultural and ornamental nursery production systems [43,44]
Toxins/chemicals produced by cover crops that are harmful to pathogens [48]
Summary
Ornamental nursery production is a lucrative segment of the green industry. In 2014, there were more than 8200 nursery producers in the US, and nursery crop sales comprised 31% of all horticultural sales, exceeding $4.2 billion [1]. The ability of nursery producers to provide pristine and blemish-free ornamental plants is greatly impacted by plant diseases [2]. Soilborne diseases are becoming more problematic, as evidenced by the substantial losses to the nursery industry observed in recent years [3,4]. Infections caused by Phytophthora spp. are commonly observed in woody ornamental nursery crops [5,6,7]. These pathogens can live several years in infected plant tissue, plant debris, soil, and water [5]. One Phytophthora species of concern to the nursery industry is Phytophthora nicotianae, which can infect 255 genera in 90 families [8]
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