Compatibility interactions between the biocontrol agent Penicillium frequentans Pf909 and other existing strategies to brown rot control

[Background] To improve efficacies achieved through biocontrol agent application, there has been increasing interest in studying the efficacy of biocontrol agent with other existing technologies like chemicals or different biocontrol agent combinations. The compatibility of Penicillium frequentans (Pf909) with modern inputs in plant protection like fungicides (chemicals and biologicals) and insecticides is a pre-requisite for developing integrated brown rot management strategies. [Results] The combination of P. frequentans and Bacillus amyloliquefaciens, each with different mechanisms of action, competition and antibiosis, respectively, did not improve the biocontrol of brown rot when each treatment was applied individually. P. frequentans and B. amyloliquefaciens could not be combined together in the same tank, because bacteria inhibited the germination and growth of P. frequentans tubes in suspension. Furthermore, B. amyloliquefaciens also competes with P. frequentans once applied on fruit surfaces. Additionally, bacteria reduced the growth of P. frequentans CFUs on media, at different 25 °C and 30 °C throughout the incubation periods. However, 76% of fungicides and 90% of insecticides commonly used against stone fruit pests are compatible with P. frequentans. [Conclusions] Results indicated that the most commercial chemical pesticides could be simultaneously applied with Pf909 in integrated pest control, but not B. amyloliquefaciens.