Sensitivity of Monilinia fructicola from Spanish peach orchards to thiophanate-methyl, iprodione, and cyproconazole: fitness analysis and competitiveness

Abstract

Benzimidazoles, dicarboximides and demethylation inhibitors are the main group of fungicides used to control brown rot in Spain. The causal agents of brown rot in peach (Prunus persica (L.) Batsch) orchards in Spain are Monilinia laxa M. fructigena, and M. fructicola. The dynamics of fungicide sensitivity and fitness of M. fructicola population, the most recent species causing brown rot in the Ebro Valley (Lleida, Spain), were characterized by determining their resistance, fitness, and in vitro competitiveness to thiophanate-methyl (TM), iprodione (I), and cyproconazole (CPZ) in field isolates recovered over the 2006-2010 period. We found that: (a) more than 95 % of the M. fructicola isolates are high TM-resistant, (b) more than 50 % of the M. fructicola isolates are Iresistant and these frequencies of occurrence did not change during our 5-year survey, and (c) a few CPZresistant isolates have been also detected in population since 2008. We identified five different fungicideresistant (R) and/or fungicide-sensitive (S) phenotypes and found that our study population contains multiple fungicide-resistant isolates. Moreover, these fungicideresistant isolates display high parasitic fitness on fruit and flowers and high competitiveness. These findings suggest that the TM, I, and CPZ resistance of M. fructicola isolates could be contributing as another factor on changing the frequency of occurrence of the three Monilinia species in the Ebro Valley.

Peach Brown Rot: Still in Search of an Ideal Management Option

“…Egüen et al [18] suggested that fungicide resistance of the M. fructicola population is co-acting with other factors such as an adaptation in the pathogen, changing the frequency of occurrence of the three Monilinia species in Spain. The displacement of M. laxa by M. fructicola in Spain has also been attributed to its conjugational potency related to sexual exchange and ability to produce ascopores from pseudosclerotial mummified fruits and their gradual process of a sexual propagation [56].…”

“…Synthetic fungicides such as cyproconazole, iprodione, and thiophanate-methyl [18], have been used to control Monilinia in the orchards in conventional and integrated pest management programs depending of the country. As an example in the European Union, the main conventional products, allowed in Spain including application doses and maximum residue limit (MRL) for European countries is shown in Table 4.…”

“…In some cases, the disease has been associated with up to 80% of the incidence of fruit loss after harvest [18,19], mostly under favorable environmental conditions for the commencement and growth of the diseases in the orchard.…”

Epidemiología y control de la podredumbre parda del melocotón en postcosecha

“…However, fungicide-based methods are not sustainable in the long term because of the emergence and subsequent spread of M. fructicola and M. laxa strains with reduced sensitivity to fungicides (Egüen et al, 2015;Ma et al, 2005;Malandrakis et al, 2013;Thomidis et al, 2009;Weger et al, 2011;. Recent studies in the Ebro Valley have detected a M. fructicola population with isolates that were single resistant, double resistant, or even triple resistant to tiophanate-methyl, iprodione and tebuconazole (Egüen et al, 2015).…”

“…Recent studies in the Ebro Valley have detected a M. fructicola population with isolates that were single resistant, double resistant, or even triple resistant to tiophanate-methyl, iprodione and tebuconazole (Egüen et al, 2015). And M. laxa populations single, or double resistant to tiophanate-methyl, and iprodione (Egüen et al, 2016).…”