Influence of Biocontrol and Integrated Strategies and Treatment Timing on Plum Brown Rot Incidence and Fungicide Residues in Fruits

Brown rot caused by Monilinia spp. is the main disease of stone fruits. Our research aimed to identify an appropriate strategy to control plum brown rot and reduce fungicides residues in fruit through targeted application of the biocontrol agents (BCAs) Papiliotrema terrestris and Bacillus subtilis, alone or in combination with synthetic fungicides. The following treatments were evaluated: Biological (BIO1, BIO2), Integrated (INT1, INT2, INT3), and Combined (COMB), all compared with Chemical strategy. Five key treatments (seven for BIO2) were performed in the crucial phenological stages for the disease cycle: INT1, INT2, and INT3 approaches consisted, from the beginning of the season, of one, two, or three treatments, respectively, alternately with boscalid or cyprodinil followed by applications of BCA until the fruit harvest. After harvest, plums were subjected to an additional treatment with the two BCAs and the fruits were stored at 20 °C for 15 days. The results obtained by applying our BCA PT22AV, revealed, in the field and in postharvest, the highest level of disease protection with management strategies BIO2 (94.8–97.2% in field; 65–84% in postharvest) and INT3 (95.5–97% in field and 63% to 91% in postharvest). The level of fungicide residues in fruit was zero in BIO strategies and lower in INT strategies as compared to chemical strategy.