Enhancing the adhesion of Epicoccum nigrum conidia to peach surfaces and its relationship to the biocontrol of brown rot caused by Monilinia laxa

Abstract

To find a formulation of Epicoccum nigrum conidia that enhances its adhesion to peach surfaces and improves its biocontrol efficacy against brown rot caused by Monilinia laxa. The stickers, glycerol, sodium alginate and methylcellulose; the desiccants, silica powder and talc; and a commercial adhesive (NU FILM 17) were added at two different points during the production of an E. nigrum conidial formulation to improve conidial adhesion to peach surfaces. Conidial adhesion levels were determined from the number of E. nigrum conidia that adhered to glass slides or peach surfaces and conidial viability of adherent E. nigrum conidia was determined from the number of colony-forming units of glass or peach-adherent E. nigrum that grew on Petri dishes that contained potato dextrose agar. Compared to dried E. nigrum conidia without additives, the adhesion and viability of adherent E. nigrum conidia to peach surfaces were enhanced when either 1.25% sodium alginate or 2.5% methylcellulose was added to the conidial mass after fluid-bed drying, and when 2.5% methylcellulose was added to the conidial mass after its production and before fluid-bed drying. Epicoccum nigrum conidial formulations with 2.5% methylcellulose were more effective than dried E. nigrum conidia without additives in reducing the incidence of brown rot in peaches caused by M. laxa. When 2.5% methylcellulose is incorporated into an E. nigrum conidial formulation, the adhesion of E. nigrum conidia to peach surfaces improves and results in efficacious biocontrol of brown rot. A new improved formulation of a biocontrol agent has been developed to improve the control of M. laxa on peaches.