Biocontrol Science and Technology (2002) 12, 547±553 Improving Biocontrol Activity of Pichia guillermondii Against Post-harvest Decay of Oranges in Commercial Packing-houses by Reduced Concentrations of Fungicides GIOVANNI ARRAS, 1 BARBARA SCHERM 2 and QUIRICO MIGHELI 2 1 CNRÐIstituto di Scienze delle Produzioni Alimentari, Via dei Mille 48, I- 07100 Sassari, Italy; 2 Dipartimento di Protezione delle Piante, UniversitaÁ di Sassari, Via E. De Nicola 9, I-07100 Sassari, Italy (Received 14 February 2002; returned 11 March 2002; accepted 10 April 2002) Three commercial tests were conducted in 2000±2001 in two commercial packing-houses (Muravera and Villacidro) located in Sardinia, Italy, to evaluate the eYcacy of biological, chemical and integrated treatments against Penicillium digitatum and P. italicum on naturally inoculated orange fruit. Damage caused by the packing-hous e processing line was also assessed. Treating orange fruits with the yeast Pichia guilliermondi i (strain 5A) in the processing line generally led to a signiWcant reduction of post-harvest decay compared to the processed control, while the commercial product Aspire Ò , based on Candida oleophila, was ineVective in inhibiting the pathogen when applied alone. The integrated application of thiabendazole or imazalil with the biocontrol agents signiWcantly improved the control of fruit decay. Using thiabendazole at concentrations of 0.1 and 1.2 g L 2 1 , led to similar inhibition of fruit decay in two trials. Both yeasts were equally able to colonize the fruit actively during storage. Passing fruits through the packing line caused a signiWcant increase in fruit decay. Keywords: orange, post-harvest decay, Penicillium spp., antagonistic yeast, fungicides INTRODUCTION Penicillium digitatum Sacc. (green mould) and P . italicum Wehmer (blue mould) decays can cause heavy post-harvest losses in citrus fruits. These pathogens mainly infect fruit through epicarpic wounds caused during harvesting and handling in the packing-hous e processing lines, and are usually controlled by chemicals such as thiabendazole, imazalil or sodium orto-phenylate (Eckert & Ogawa, 1985). However, the development of fungicide resistance by post-harvest citrus pathogens (Vloutoglou et al., 1993; Eckert et al., 1994; Holmes & Eckert, 1995, 1999) and an increasing environmental concern over pesticide residues in food, has prompted an urgent need for alternative control measures. Under such circumstances, Correspondence to: Q. Migheli. Tel: + 39 079 229295; Fax: + 39 079 229316; E-mail: migheli@uniss.it ISSN 0958-3157 (print)/ISSN 1360-047 8 (online)/02/050547-07 © 2002 Taylor & Francis Ltd DOI: 10.1080/095831502100001621 6