Effect of Timing of Application of the Biological Control Agent Microsphaeropsis ochracea on the Production and Ejection Pattern of Ascospores by Venturia inaequalis

Abstract

Field and in vitro trials were conducted to establish the influence of the biological control agent Microsphaeropsis ochracea on the ejection pattern of ascospores by Venturia inaequalis and on apple scab development, and to establish the best timing of application. The ejection pattern of ascospores was similar on leaves sprayed with M. ochracea and on untreated leaves. Fall application of M. ochracea combined with a delayed-fungicide program was evaluated in orchards with intermediate and high scab risk. For both orchards, it was possible to delay the first three and two infection periods in 1998 and 1999, respectively, without causing significant increase or unacceptable leaf and fruit scab incidence. To evaluate the best timing of application, sterile leaf disks were inoculated with V. inaequalis and then with M. ochracea 0, 2, 4, 6, 8, 10, 12, 14, and 16 weeks later. After incubation under optimal conditions for pseudothecia development, the number of ascospores was counted. Similarly, M. ochracea was sprayed on scabbed leaves on seven occasions from August to November 1999 and 2000. Leaves were overwintered on the orchard floor and ascospore production was evaluated the following spring. Ascospore production was reduced by 97 to 100% on leaf disks inoculated with M. ochracea less than 6 weeks after inoculation with V. inaequalis, but ascospore production increased with increasing period of time when M. ochracea was applied 8 to 16 weeks after the inoculation with V. inaequalis. In the orchard, the greatest reduction in production of ascospores (94 to 96% in 2000 and 99% in 2001) occurred on leaves sprayed with M. ochracea in August. The production of ascospores was reduced by 61 to 84% in 2000 and 93% in 2001 on leaves sprayed with M. ochracea in September, reduced by 64 to 86% in 2000 and 74 to 89% in 2001 on leaves sprayed in October, and reduced by 54 and 67% in 2000 and 2001, respectively, on leaves sprayed in November. It was concluded that M. ochracea should be applied in August or September and that ascospore maturation models and delayed-fungicide program could be used in orchards treated with this biological control agent.

Latent postharvest pathogens of pome fruit and their management: from single measures to a systems intervention approach

“…However, further research is still needed to understand: (i) the relationships between the accumulation of pathogen inoculum on the various substrates over time, (ii) the relative importance of different substrates as inoculum sources for fruit infections, and (iii) infection periods on developing fruits in the orchard. Eventually, this knowledge can be used for the development of sanitation measures (Holb 2006;Llorente et al 2010), or measures to stimulate beneficial microbiome inhabitants on those substrates that can antagonize pathogen colonization, survival and sporulation (Carisse and Rolland 2004;Llorente et al 2006Llorente et al , 2010Rossi and Pattori 2009).…”

Biocontrol of Stemphylium vesicarium and Pleospora allii on Pear by Bacillus subtilis and Trichoderma spp.: Preventative and Curative Effects on Inoculum Production

“…BCAs should be evaluated for their effect on inoculum production (conidia, pseudothecia, ascospores), and the strategy for their application in relation to the growth of S. vesicarium and colonization of leaf debris, should be defined before being included in an integrated disease management program. Timing of application may be critical for biological fungicides [17]. For these reasons, the efficacy of BCAs based on B. subtilis and Trichoderma spp.…”

Dynamics of post‐harvest pathogens Neofabraea spp. and Cadophora spp. in plant residues in Dutch apple and pear orchards

“…Further, this knowledge could be used for the development of focused sanitation measures (Holb, ; Gomez et al ., ; Llorente et al ., ). Understanding the role of microbial colonizers in competitive substrate colonization (Köhl et al ., ) will allow the development of measures to stimulate beneficial components of microbiomes or to apply beneficial antagonistic strains to the relevant plant residues, with the aim of suppressing pathogen colonization, survival and sporulation (Carisse & Rolland, ; Llorente et al ., ; Rossi & Pattori, ).…”