Efficacy of some strobilurins in controlling citrus fruit decay [clementines; mandarins]

English. The efficacy of three strobilurins, azoxystrobin (AZO), kresoxim-methyl (KRE) and trifloxystrobin (TRI), in comparison with imazalil (IMZ), was evaluated. A first trial, using Nules clementines, was carried out in order to verify the effectiveness of strobilurins at different concentrations. In a second one with Malvasio mandarins stored at 20 deg C for 6 weeks, the three strobilurins and IMZ were used in combination with an antitranspirant (Fitotherm). Finally, a third experiment was set up in order to verify the different response of the three strobilurins and IMZ on fruit previously infected with 10E4 spores of P. italicum or P. digitatum. In the first trial, no beneficial effect of increasing concentrations of the active ingredients was found; KRE was the only one effective at some extent against Phytophthora. In the second trial, all the fungicides gave positive results in reducing decay, with KRE and AZO being the most effective, with an average percentage of rotten fruit of 4%, against 6% of IMZ, 8% of TRI and 17 % of control. Fitotherm decreased the incidence of decay in untreated fruits and showed a significant interaction with the single fungicides, increasing significantly their efficacy. The results of the third experiment confirmed the efficacy of IMZ (2% of decay), AZO and KRE (4% of decay), while the response of TRI, with 7 % of decay against 1 % of control, was disappointing. Fruits inoculated with P. italicum did not show more decay than control, whilst the ones infected with P. digitatum from the second week of storage on exhibited a higher decay

Italian. E´ stata valutata l´efficacia di azoxysytobin, kresoxim-methyl e trifloxystrobin per il controllo dei marciumi degli agrumi, in confronto con imazalil. Una prima prova ha confermato la capacità delle strobilurine di agire a dosi molto basse contrastando efficacemente lo sviluppo dei penicilli; kresoxim-methyl si è dimostrato l´unico principio attivo efficace nei confronti di Phytophthora. In un secondo esperimento su mandarino Malvasio conservato a 20 gradi C per sei settimane, i tre fungicidi, utilizzati in combinazione con un antitraspirante (Fitotherm), hanno ridotto i marciumi rispetto al controllo, con risultati simili a quelli ottenuti con imazalil. Fitotherm ha determinato una diminuzione dell´incidenza dei marciumi nei frutti non trattati e ha evidenziato un´interazione significativa con i singoli fungicidi, aumentandone l´efficacia. In un successivo esperimento, condotto su frutti infettati con una sospensione conidica di Penicillium digitatum o di Penicillium italicum, imazalil, azoxystrobin e kresoxim-methyl hanno confermato la loro efficacia, mentre deludente è stata la risposta di trifloxystrobin. I frutti inoculati con P. italicum non sono risultati soggetti a marciumi in misura maggiore rispetto al controllo, mentre quelli infettati con P. digitatum dalla seconda settimana di conservazione in poi hanno presentato maggiori marciumi