Pre- and post-infection activity of new fungicides against Botrytis cinérea and other fungi causing decay of table grapes

Cien. Inv. Agr. 34(3): 215-224. 2007 www.rcia.puc.cl ARTICULO DE INVESTIGACION Pre- and post-infection activity of new fungicides against Botrytis cinerea and other fungi causing decay of table grapes Ricardo A. Serey, René Torres, and Bernardo A. Latorre1 Facultad de Agronomía e Ingeniería Forestal, Pontificia Universidad Católica de Chile Casilla 306-22, Santiago, Chile Abstract R.A. Serey, R. Torres, and B.A. Latorre. 2007. Pre- and post-infection activity of new fungicides against Botrytis cinerea and other fungi causing decay of table grapes. Cien. Inv. Agr. 34(3):215-224. Pre- and post-harvest diseases restrict table grape production and exports (Vitis vinifera L.) in Chile, with the most important disease being grey mold (Botrytis cinerea). In addition, rot due to Aspergillus niger, Cladosporium herbarum, Penicillium expansum, and Rhizopus stoloniferr frequently occurs. The pre- and post-infection activity of fungicides against these pathogens was studied on Thompson Seedless table grapes. Detached, mature, berries were used, and inoculations were performed with 20 μL of a 106 spores·mL-1 suspension placed on three punctures aseptically made at the calyx end of each berry. Fungicides used (per liter) were boscalid (600 mg), boscalid (200 mg) + pyraclostrobin (100 mg), boscalid (200 mg) + kresoxim methyl (100 mg), cyprodinil (60 mg) + fludioxonil (40 mg), BAS 600 KBF (100 mg) + metrafenone (150 mg), BAS 600 KBF (200 mg) + boscalid (300 mg), BAS 600 KBF (100 mg) + pyraclostrobin (100 mg), and captan (400 mg). Each fungicide was applied either by drop (12 μL·berry-1) placed on three punctures made with a sterile hypodermic needle or by 60 s immersion. Berries were then incubated in humid chambers at 20ºC. The pre-infection (protection) activity of the fungicides varied considerably among the pathogens tested and was found to be significant (p < 0.001) and, with one exception (A. niger), it was significantly (p < 0.002) affected by the application method. The interaction between fungicide and application method was only significant (p < 0.001) for R. stolonifer at 48 h post treatment. In general, pre-infection activity gave 0 to 4 days protection after drop applications and 0 to 21 days after immersion treatments. The post-infection (curative) activity varied among pathogens and fungicide treatments. However, it was always below 24 h. Key words: Blue mold, curative activity, gray mold, protection activity, sour rot, Vitis vinifera. Introduction Decays are one of the main factors restricting the production and commercialization of table grapes (Vitis vinifera L.) in Chile and other countries (Franck et al., 2005; Lydakis and Aked; 2003; Lichter et al., 2002). Important economic losses usually occur during harvest, cold storage, and transportation of Chilean table grapes to markets in North America, Europe and Asia (Franck et al., 2005; Donoso and Latorre, 2006). Received 07 April 2007. Accepted 11 August 2007. 1 Corresponding author: Botrytis cinerea Pers. is the most important pathogen affecting table grape production in Chile. Infections start from the inoculum present in the vineyard which can develop into latent infections with disease appearing later in packed table grapes during storage and transportation. Additionally, pre and post harvest decay caused by Aspergillus niger Tiegh, Cladosporium herbarum (Pers.) Link, Penicillium expansum Link and Rhizopus stoloniferr (Ehrenb.) Vuill, has been reported in Chile and elsewhere (Hewitt, 1988; Zahavi et al., 2000; Latorre et al., 2002b). 216 CIENCIA E INVESTIGACION AGRARIA Fungicide treatments applied in the vineyard are important to prevent decay development at harvest or during post-harvest (Latorre et al., 2001; Franck et al., 2005). However, registration restrictions, tolerances established by import countries, and the development of resistant strains limit their use in table grapes and other fruit crops (Latorre et al., 1994; Latorre et al., 2002a; Errampalli and Crnko, 2004; Sallato and Latorre, 2006). Therefore, new, effective fungicide treatments with the lowest possible toxicological risk are required, as has been proposed elsewhere (Adaskaveg et al., 2005; Förster et al., 2007; McGrath, 2004). Fungicides can provide disease control through both pre- and post-infection activity. Pre-infection activity is commonly known as protectant (preventive) activity and postinfection activity comprises a curative action that can involve both pre- and post-symptom expression activities. The modes of actions of the fungicides used in this study are varied. Anilinopyrimidines inhibit methionine biosynthesis and secretion of hydrolytic enzymes. Carboximides inhibit succinate dehydrogenase in the cell respiration process. Phenylpyrrol inhibits histidine quinase. Phthalimides are multisite inhibitors. Strobilurines (Qo inhibitor fungicides, QoI) act at the quinone binding site of the cytochrome bc1 complex in the mitochondrial cell membrane. Triazolopyrimidins have an unknown mode of action (McGrath, 2004; FRAC, 2007). Understanding a fungicide’s mode of action and also whether it has activity both pre- and post-infection contributes considerably to improved control efficiency through optimizing application timing based on the host-pathogeninteractions in table grapes and other hosts (Szkolnik, 1978; Jones and Latorre, 1985; Wong and Wilcox, 2001; Rebollar-Alviter et al., 2007). Therefore, the objectives of this study were to evaluate, under laboratory conditions, the preinfection and post-infection activity of boscalid, captan, cyprodinil, and the new fungicide BAS600 against B. cinerea, P. expansum, R. stolonifer, r A. nigerr and C. herbarum, which are the main filamentous fungi associated with pre- and post-harvest decay of table grapes in Chile. Materials and methods Table grapes All the experiments were conducted on healthy and mature ‘Thompson Seedless’ table grapes (total soluble solids >16%). Berries with their pedicel intact and without fungicide treatments were obtained from a commercial farm. Prior to every experiment, the berries were superficially disinfected with 0.025% sodium hypochlorite for 3 min. They were washed in tap water and were aseptically distributed on grids in polyethylene chambers (34 x 25 x 13 cm) at 20ºC and 93-96% relative humidity (RH). The RH was obtained by moistening a double paper layer placed at the bottom of each chamber. Relative humidity was verified with a HOBO sensor (Bourne, Massachussets, USA), located inside the chamber. Isolation and inoculation Isolates of B. cinerea, P. expansum, and A. niger were obtained from ‘Thompson Seedless’ table grapes. Cladosporium herbarum was obtained from ‘Red Globe’ berries, and R. stolonifer from strawberries. Pure cultures were obtained by sub-cultivating hyphal tips in potato dextrose agar acidified with 0.5 mL·L-1 of 90% lactic acid (APDA) at 20ºC. All isolates were pathogenic to table grapes. The inoculum was prepared with spores obt (...truncated)