Comparative performance of sanitizers in managing plant-to-plant transfer and postharvest infection of Calonectria pseudonaviculata and Pseudonectria foliicola on Boxwood

Authors: BIKA, RAVI - Tennessee State University; Copes, Warren; BAYSAL-GUREL, FULYA - Tennessee State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2021
Publication Date: 4/27/2021
Citation: Bika, R., Copes, W.E., Baysal-Gurel, F. 2021. Comparative performance of sanitizers in managing plant-to-plant transfer and postharvest infection of Calonectria pseudonaviculata and Pseudonectria foliicola on Boxwood. Plant Disease. https://doi.org/10.1094/PDIS-03-21-0481-RE.
DOI: https://doi.org/10.1094/PDIS-03-21-0481-RE

Interpretive Summary: oxwood blight and Volutella blight are serious threats to boxwood production and the cut boxwood greenery market. Both pathogens often cause significant economic loss to all parties (growers to retailers) in the horticultural marketing chain. The objective of this study was to evaluate efficacy of commercially available disinfecting and cleaning products for preventing plant-to-plant transfer of the two pathogens on the cutting blades of pruners and maintaining quality of shipped boxwood greenery. Three commercial disinfectants containing quaternary ammonium compounds (QAC) were the most effective in reducing plant to plant transfer of boxwood blight and Volutella blight pathogens on pruner blades. The same three products, as well as 2.5% acetic acid (Vinegar), 10% bleach, and 2% potassium peroxymonosulfate + NaCl, maintained postharvest shelf life of cut boxwood greeneries exposed to the boxwood blight pathogen. The same three products, as well as a common commercial cleaner with a QAC , maintained postharvest shelf life of cut boxwood greeneries exposed to the Volutella blight pathogen. This information provides information that will benefit extension personnel, crop advisers, and growers of ornamental crops.

Technical Abstract: Calonectria pseudonaviculata and Pseudonectria foliicola causing infamous ‘boxwood blight’ and ‘Volutella blight’, respectively, are constantly threatening the boxwood production and cut boxwood greenery market. Both pathogens often cause significant economic loss to all parties (growers-retailer) in the horticultural chain. The objective of this current study was to evaluate efficacy of disinfecting chemicals [quaternary ammonium compound (QAC), peroxy, acid, alcohol, chlorine, cleaner] in preventing plant-to-plant transfer of C. pseudonaviculata and P. foliicola from cutting tools, as well as reducing postharvest boxwood blight and Volutella blight disease severity in harvested boxwood greenery. First, an in-vitro study was conducted to select products and doses that completely or near-completely inhibited conidial germination of C. pseudonaviculata and P. foliicola. The selected treatments were further studied in reducing the plant-to-plant transfer of C. pseudonaviculata and P. foliicola and managing postharvest boxwood blight and Volutella blight in boxwood rooted cuttings. For the plant-to-plant transfer study, Felco 19 shear was used as a tool for mechanical transfer of fungal conidia. The blade of Felco 19 shear was exposed to conidial suspension of C. pseudonaviculata or P. foliicola by cutting a 1 cm diameter cotton roll that was initially dipped into fungal suspension. The test boxwood rooted cuttings (10 cm height) were pruned with the shear. Felco 19 shears were equipped with a mounted miniature sprayer connected to pressurized reservoir of treatment solution that automatically sprayed the blade and plant surface while cutting. The influence of accumulated sap on the shear blade was studied through 1 and 10 cuts on test plants while screening efficacy of treatments. Then, the boxwood rooted cuttings were transplanted and incubated in room conditions (21 °C, 60% RH) with 12 h of fluorescent light; data evaluation on disease severity was done weekly for a month. Disease progress [area under disease progress curve (AUDPC)] was calculated. In another study, postharvest dip application of treatments was used for the management of postharvest boxwood blight or Volutella blight on cut boxwood greeneries. The harvested boxwood cuttings were dipped into treatment solution 3 days after inoculation using conidial suspension of C. pseudonaviculata or P. foliicola. Then, the boxwood cuttings were kept in room conditions; boxwood blight or Volutella blight disease severity as well as marketability (postharvest shelf life) of boxwood cuttings were assessed for a week every 2 days. A significant difference between the treatments were observed in reducing boxwood blight or Volutella blight disease severity and AUDPC. The treatments (ODD + DoD + DdD + DB)AC [Simple green d pro 5], 2 propanol + DDAC (0.12%) [KleenGrow], and DBAC + DEAC [GreenShield] were the most effective in reducing the plant to plant transfer of boxwood blight and Volutella blight when pruned with contaminated Felco 19 shear as cutting tool. In addition to above three effective treatments, acetic acid (2.5%) [Vinegar], 2-propanol + DDAC (0.06%), sodium hypochlorite (Clorox) and potassium peroxymonosulfate + NaCl (2%) [Virkon] were effective in reducing postharvest boxwood blight whereas DBAC + DBAC [Lysol all-purpose cleaner] and DDAC +DBAC [Simple green d pro 3 plus] were effective in reducing Volutella blight disease severity and AUDPC as well as maintained the better quality and longer postharvest shelf life of cut boxwood greeneries when applied as dip treatment. The longer postharvest shelf life of cut boxwood greeneries may be attributed to reduced disease severity and AUDPC resulting healthy physiological functioning boxwood cuttings.