The significant problems caused by soilborne pathogens in crop production worldwide include reduced crop performance, decreased yield, and higher production costs. In many parts of the world, methyl bromide was extensively used to control these pathogens before the implementation of the Montreal Protocol—a global agreement to protect the ozone layer. The threats of soilborne disease epidemics in crop production, high cost of chemical fungicides and development of fungicide resistance, climate change, new disease outbreaks and increasing concerns regarding environmental as well as soil health are becoming increasingly evident. These necessitate the use of integrated soilborne disease management strategies for crop production. This article summarizes methods for management of soilborne diseases in crop production which includes the use of sanitation, legal methods, resistant cultivars/varieties and grafting, cropping system, soil solarization, biofumigants, soil amendments, anaerobic soil disinfestation, soil steam sterilization, soil fertility and plant nutrients, soilless culture, chemical control and biological control in a system-based approach. Different methods with their strengths and weaknesses, mode of action and interactions are discussed, concluding with a brief outline of future directions which might lead to the integration of described methods in a system-based approach for more effective management of soilborne diseases.

Cover crops represent a potential tool for suppression of soil borne diseases in woody ornamental nursery production, which can cause significant economic losses. Field experiments were conducted in 2019 and 2020 to explore the effects of a cover crop and the timing of cover crop disturbance on soilborne disease suppression. Soils from red maple (Acer rubrum ‘October Glory’) plantations grown with or without a cover crop [crimson clover (Trifolium incarnatum)] were sampled following senescence of the cover crop. Greenhouse bioassays were conducted using red maple cuttings on inoculated (with Rhizoctonia solani, Phytopythium vexans or Phytophthora nicotianae) and non-inoculated field soils. Plant height, total and root fresh weight were measured, and the roots were assessed for disease severity on a 0 to 100% root damage scale. Pathogen recovery was assessed by culturing root pieces (~1 cm length) on oomycetes or Rhizoctonia semi-selective media. Soil samples were analyzed for organic matter, nitrogen, phosphorus, potassium, pH and Pseudomonad population count. A minimal effect of cover crop disturbance timing (late fall or early spring) was found on disease suppression. Cover crop usage reduced disease severity and pathogen recovery in red maple field soils. Plants grown in cover cropped soil had greater total, root and aboveground fresh weight compared with those from non-cover cropped soil, but plant height was not affected. Cover crops increased soil organic matter and total nitrogen in 2020. Pseudomonad populations were higher when cover crops were used. The results suggest that cover crops can reduce soilborne disease in woody ornamentals.

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 a woody ornamental nursery production system. The objective of this study was to explore the impact of winter cover crops usage on soilborne disease management in that system. Soils from established field plots of red maple (Acer rubrum L.) with and without winter 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 Phytopythium vexans, Phytophthora nicotianae or Rhizoctonia solani) and non-inoculated field soils. The results indicated that winter cover crop usage was helpful for inducing soil disease suppressiveness. There was lower disease severity and pathogen recovery when the cover crops were used compare to the non-cover cropped soil. However, there were no differences in maple plant fresh weight and root weight between the treatments. The rhizosphere pseudomonad microbial population was also greater when the cover crops were used. Similarly, the 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. Therefore, stakeholders can consider cover crop usage as an alternative sustainable management tool against soilborne diseases in field nursery production system.

Bacterial spot is one of the most serious diseases of peach caused by the pathogen Xanthomonas arboricola pv. pruni (XAP), leading to early defoliation and unmarketable fruit. The pathogen can overwinter in peach twigs and form spring cankers, which are considered the primary inoculum source for early season leaf and fruitlet infection. The amount of overwintering bacterial inoculum plays a critical role for the bacterial spot development, but no reliable quantification method is available. Thus, we developed a long-amplicon propidium monoazide (PMA)–quantitative PCR (qPCR) assay for specific detection of viable XAP cells. The optimized PMA-qPCR assay used 20 μM of PMAxx for pure bacterial suspensions and 100 μM for peach twig tissues. The Qiagen Plant Pro Kit with an additional lysozyme digestion step was the DNA extraction protocol that yielded the best detection sensitivity with the bacteria-spiked peach twig extracts. The PMA-qPCR assay was tested with different mixtures of viable and heat-killed XAP cells in pure bacterial suspensions and bacteria-spiked peach twig tissues. The results showed that this assay enabled sensitive, specific, and accurate quantification of viable XAP cells as low as 10³ CFU/ml with the presence of up to 10⁷ CFU/ml of dead XAP cells, while suppressing the amplification of DNA from dead cells. For mixtures of viable and dead cells, the PMA-qPCR results were linearly correlated with the predicted concentrations of viable XAP (R² > 0.98). Thus, the PMA-qPCR assay will be a suitable tool for quantifying overwintering XAP population on peach trees.

Management of plant diseases is a subject of concern for researchers as well as growers. Different management practices are being developed and used to combat the rising number of plant pathogens, which threaten nursery crop production. Use of cover crops for sustainable management of soilborne diseases is being explored as an alternative strategy to the chemicals. However, the potential threat of these cover crops acting as a secondary host of these devastating soilborne pathogens has not been described. We studied the response of the major cover crops being used by woody ornamental growers in the Southeastern United States to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani in greenhouse conditions to identify the effective cover crops that can be used in a nursery field production system. Data related to post-emergence damping-off and plant growth parameters (plant height increase and fresh weight) were recorded. Similarly, cover crop roots were assessed for root rot disease severity using a scale of 0–100% roots affected. Among the tested cover crops, the grass cover crops triticale (×Triticosecale Wittm. ex A. Camus.), annual ryegrass (Lolium multiflorum L.), Japanese millet (Echinochloa esculenta (A. Braun) H. Scholz), and the legumes Austrian winter pea (Pisum sativum var. arvense (L.) Poir) and cowpea ‘Iron and Clay’ (Vigna unguiculata (L.) Walp.), showed lower root rot disease severity and post-emergence damping-off in the soil inoculated with P. nicotianae, R. solani, or P. vexans compared to the other crops. Since these cover crops can act as non-host crops and benefit the main crop in one way or another, they can be used in the production system. Further research is recommended to evaluate their performance in a natural field setting.

The cut flower business has been growing rapidly worldwide, with a positive and significant impact on the economies of many countries. Maintaining quality and extending the vase life of cut flowers are crucial aspects of the floral industry. Synthetic preservatives (silver nitrate, silver thiosulfate, nano-silver, hydroxy quinoline, thiabendazole, and aluminum compounds) have been commercially used in the vase to maintain the quality and longevity of cut flowers for a long time. However, these preservatives may persist in the environment, causing severe health hazards and environmental pollution, and are also expensive. Therefore, cut flower industries seek low-cost, eco-friendly, and safer alternatives. In this context, natural preservatives (NPs), including plant extracts (PEs) and essential oils (EOs), offer a promising and sustainable alternative to synthetic preservatives in the vase. This review highlights the potential NPs and their role in enhancing the quality and vase life of cut flowers. We discussed how these preservatives exert their beneficial effects, such as inhibiting microbial growth, reducing ethylene production, and enhancing water uptake, and also explored the potential issues associated with them. We conducted a structured literature review and summarized the most commonly used EOs and PEs, their optimal dosages, efficacy, and combinations, and concluded with future directions to enhance the vase life of cut flowers sustainably.