Ž . International Journal of Food Microbiology 70 2001 53–61 www.elsevier.comrlocaterijfoodmicro Biological control of postharvest pear diseases using a bacterium, Pantoea agglomerans CPA-2 C. Nunes ) , J. Usall, N. Teixido, I. Vinas ´ ˜ PostharÕest Unit, Centre UdL-IRTA, 177 RoÕira Roure AÕenue, 25198 Lleida, Catalonia, Spain Received 10 June 2000; received in revised form 12 February 2001; accepted 5 April 2001 Abstract Epiphytic microorganisms isolated from the fruits and leaf surfaces of apples and pears were screened for antagonistic activity against Penicillium expansum on pears. From 247 microorganisms tested for antagonistic properties against P. Ž . expansum, a bacterium strain identified as Pantoea agglomerans CPA-2 was selected. This bacterium was very effective Ž 7 against Botrytis cinerea, P. expansum and Rhizopus stolonifer. Complete control at the three tested concentrations 2 =10 , 7 8 y1 . 3 4 5 y1 8 =10 and 1 =10 CFU ml was obtained on wounded pears inoculated with 10 , 10 and 10 conidia ml of P. expansum and R. stolonifer. At 8 =10 7 CFU ml y1 , Pan. agglomerans reduced B. cinerea decay by more than 80% at the three concentrations of the pathogen. In over 3 years of experiments in semicommercial trials, Pan. agglomerans provided excellent control against B. cinerea and P. expansum under cold storage, either in air or in low oxygen atmospheres. Equal control was obtained with Pan. agglomerans at 8 =10 7 CFU ml y1 , as with the fungicide imazalil at commercial doses, against both pathogens. Pan. agglomerans grew well inside wounds on pears at both room and cold temperatures and under modified atmospheres. In contrast, it grew poorly on the surface of intact fruit. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Biocontrol; Pantoea agglomerans; Antagonists; Penicillium expansum; Botrytis cinerea; Rhizopus stolonifer ; Pome fruits 1. Introduction Postharvest fungal decay of pear and apple fruits Ž causes substantial economic losses in Spain Palazon ´ . et al., 1984 . Blue mould caused by Penicillium expansum is the most important postharvest disease Ž . of pome fruits worldwide Pierson et al., 1971 , followed in Spain by Botrytis cinerea and Rhizopus Ž . stolonifer Palazon et al., 1984 . ´ ) Corresponding author. Tel.: q 34-973-702-660; fax: q 34-973- 238-301. Ž . E-mail address: nunes.carla@mail.telepac.pt C. Nunes . Postharvest fungicide treatments are the main means of controlling these losses. The development of resistant strains of the pathogens to many fungi- Ž cides Spotts and Cervantes, 1986; Vinas et al., ˜ . 1991, 1993 and the growing concern for human Ž safety and protection of the environment Norman, . 1988; Wisniewski and Wilson, 1992 have resulted in the need to develop other methods to control postharvest decay. Biological control of storage decay using a micro- bial antagonist has been considered a desirable alter- native to synthetic fungicides. Postharvest biocontrol is especially feasible because harvested fruits are readily accessible to treatment with antagonists and 0168-1605r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0168-1605 01 00523-2