Efficacy of new fungicides on post-harvest bosc pear decay by Alternaria and Cladosporium in northpatagonia, Argentina

LUTZ MARIA CECILIA; SOSA MARIA CRISTINA

Simposio; III International Symposium on Postharvest Pathology; 2015

In recent years, decay by Alternaria spp. and Cladosporium spp. constituted a hazard to Bosc pear fruit during cold storage associated with significant economic losses (about 50%) in the Rio Negro and Neuquén Valleys. Studies with new fungicides that potentially have good activity against these key pathogens of Bosc pears were completed. In 2011, sensitivity to: pyraclostrobin (pyr) + boscalid (bosc) and cyprodinil (cyp) + fludioxonil (flu) in A. alternata and C. herbarum isolates was assayed according to FRAC. Doses tested were 0, 0.1,1, 10 and 100 µg/mL. Both fungicides efficiently controlled in vitro the colony mycelia growth of A. alternata (98% with cyp+flu; ED50 0.0014 µg/mL) and C. herbarum (100% with pyr+bosc, ED50: 0.00049 µg/mL). Furthermore, spore?s germination of both pathogens was significantly reduced. Efficacy of fruit decay control was evaluated. Sets of 10 fruits (times 3) were wounded, treated by immersion with fungicide (1min) and inoculated with mycelia (3x3 mm). After 7 days at 22±2ºC, both fungicides (100 µg/mL) reduced significantly the incidence by C. herbarum (85%) and A. alternata (50%). Post-harvest control assays were done by spraying with pyr+bosc and cyp+flu prepared to 0.6 and 1 gr/L, respectively on fruits in packing line in 2012. Sets of wound artificially inoculated and control fruits were stored 4 months at -1/0°C. Protective effect by fungicides in wounds inoculated with Alternaria and Cladosporium was demonstrated (%IR=98). Natural infection on non-artificially wounded fruit was reduced in 35%. The presence of inoculum in the orchard and the need to diminish rates of infection, directed the evaluation of pre-harvest spray. A set of fruits was wounded at harvest and cold stored for 2 months. Decay incidence was significantly reduced by pyr+bos (into 90%). These results are promising for the control of decay by Alternaria and Cladosporium on Bosc pears in Argentina.