pubs.acs.org/JAFC Published on Web 02/18/2010 © 2010 American Chemical Society J. Agric. Food Chem. 2010, 58, 3661–3666 3661 DOI:10.1021/jf904521f Postinfection Activity, Residue Levels, and Persistence of Azoxystrobin, Fludioxonil, and Pyrimethanil Applied Alone or in Combination with Heat and Imazalil for Green Mold Control on Inoculated Oranges MARIO SCHIRRA,* ,† AMEDEO PALMA, † ANTONIO BARBERIS, † ALBERTO ANGIONI, § VINCENZO LUIGI GARAU, § PAOLO CABRAS, § and SALVATORE D’AQUINO † † Institute of Sciences of Food Production, National Research Council, Traversa La Crucca 3, Regione Baldinca, 07100 Sassari, Italy, and § Department of Toxicology, Food and Environmental Unit, University of Cagliari, via Ospedale 72, 09124 Cagliari, Italy The postinfection activity of azoxystrobin (AZX), fludioxonil (FLU), and pyrimethanil (PYR), applied alone or in combination with imazalil (IMZ), in controlling postharvest green mold in ‘Salustiana’ oranges inoculated with Penicillium digitatum was studied. Fruits were immersed for 30 or 60 s in (i) water or water mixtures at 20 °C containing AZX, FLU, or PYR at 600 mg/L; and (ii) IMZ at 600 mg/L, alone or in combination with AZX, FLU, or PYR at 600 mg/L. Similar treatments were performed at 50 °C using the active ingredients at half rates with respect to the treatments at 20 °C. Fungicide residues in fruits were analyzed following treatments and after 14 days of simulated shelf life at 17 °C. AZX or FLU mixtures at 20 °C for 30-60 s similarly but moderately reduced green mold decay with respect to control fruit; differences due to dip time were not significant. Superior control of decay was achieved by PYR and, especially, IMZ, applied alone or in combination with AZX, FLU, or PYR. The activity of PYR at 20 °C was significantly dependent on treatment time, whereas that of IMZ and combined treatments at 20 °C was not. The effectiveness of FLU or PYR mixtures at 50 °C in controlling decay was similar and superior to that of AZX. The action of single- or double-fungicide application was not dependent on dip time in most samples. IMZ or combined mixtures at 50 °C were consistently more effective with respect to single-fungicide treatments with AZX, FLU, or PYR. The application of heated fungicide mixtures resulted in significantly higher residue accumulation in most fruit samples compared to treatments performed at 20 °C. The degradation rate of fungicides was generally low and dependent on treatment conditions such as time, temperature, and the presence or not of other fungicides. KEYWORDS: Citrus; Penicillium decay; hot water dip; reduced risk fungicides; residues INTRODUCTION Green and blue molds, respectively caused by Penicillium digitatum Sacc. and Pennicillium italicum Wehmer, are major postharvest diseases of citrus fruit worldwide ( 1 ). Postharvest management of these pathogens is mainly based on spore-load reduction through sanitation with chlorine or sodium ortho- phenylphenate (SOPP) and by control of spore germination or fungal growth with thiabendazole (TBZ) or imazalil (IMZ) ( 1 , 2 ). However, the intensive use of SOPP, TBZ, and IMZ, separately or in combination, in citrus packinghouses in various countries favored the development of single-, double-, and triple-resistant isolates of Penicillium spp. and, hence, reduced the effectiveness of these active ingredients ( 3 -5 ). Therefore, alternatives to these fungicides are required where resistant isolates have appeared to reduce the risk of selecting and spreading new resistant popula- tions of the pathogens. In recent years various effective and relatively novel com- pounds have been developed to control a wide range of fungal diseases ( 6 ). Of these, azoxystrobin (AZX), fludioxonil (FLU), and pyrimethanil (PYR) are compounds belonging to different chemical classes and thus have different modes of action against fungal pathogens ( 6 ). These compounds are classified as reduced- risk fungicides by the U.S. Environmental Protection Agency ( 7 ) and have recently been registered there also for postharvest treatment of various horticultural crops, including citrus fruit ( 8 ). Studies have been performed to evaluate the potential of these compounds in controlling postharvest decay of citrus fruit ( 8 -11 ). The comparative efficacies of AZX, FLU, and PYR were also evaluated when applied alone or in combination to lemon fruit that were wound-inoculated with P. digitatum- sensitive or -resistant to IMZ/TBZ ( 8 ). The addition of food preservatives such as sodium bicarbonate ( 12 -15 ) or potassium sorbate ( 16 ) was shown to improve their performance. In addi- tion, the residues and effectiveness of AZX ( 17 ), FLU ( 18 ), and *Corresponding author (e-mail mario.schirra@ispa.cnr.it).