Formulated Ampelomyces quisqualis CPA-9 applied on zucchini leaves: influence of abiotic factors and powdery mildew mycoparasitization

Abstract

Even though the potential of the fungus Ampelomyces quisqualis against powdery mildew has been largely demonstrated, the efficacy of the commercialised product AQ10 Biofungicide is not consistent. Recently, a solid formulation of A. quisqualis strain CPA-9 that included biodegradable coatings on its composition was developed to overcome the major shortcomings of the biocontrol agents applied under practical conditions. The aims of the present study were to show the compatibility of CPA-9 with different phytosanitary products, and to confirm the potential of this novel formulation in different approaches: (i) under different conditions of temperature (20 and 30 °C) and relative humidity (40, 60 and 85%) on different surfaces (glass and zucchini leaves), (ii) after different rainfall episodes, and (iii) verifying Podosphaera xanthii parasitization by dried conidia of CPA-9. It was demonstrated that CPA-9 was compatible with several phytosanitary products, so it might be included in integrated management programmes. Moreover, the solid formulation showed better resilience than non-formulated conidia, both applied on a glass surface and on zucchini leaves. Adherence of both treatments on zucchini leaves did not show significant differences after simulated rainfall and all tested concentrations of dried conidia were able to produce pycnidia in P. xanthii hyphae. Therefore, the developed fluidised-bed spray-dried formulation of A. quisqualis CPA-9 together with coatings compounds has all the makings of becoming a biocontrol product, although their efficacy under practical conditions should be assessed.