Sensitivities to DMI fungicides in populations of Podosphaera fusca in south central Spain

• Published in: Pest management science Vol. 66; no. 7; pp. 801 - 808
• Main Authors: López-Ruiz, Francisco J, Pérez-García, Alejandro, Fernández-Ortuño, Dolores, Romero, Diego, García, Emilio, de Vicente, Antonio, Brown, James KM, Torés, Juan A
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.07.2010; Wiley; Wiley Subscription Services, Inc
• Subjects: application rate; azoles; Biological and medical sciences; Control; Crop production; Crops; cross-resistance; cucurbits; Demethylation; Disease control; Drug Resistance, Fungal - drug effects; fenarimol; Flowers & plants; frequency; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; fungicide resistance; Fungicides; Fungicides, Industrial - toxicity; geographical variation; Indexing in process; mechanism of action; Methylation - drug effects; myclobutanil; Pathogens; Pest control; Pesticides; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - microbiology; plant pathogenic fungi; Podosphaera; Podosphaera fusca; Podospora - drug effects; Podospora - metabolism; Podospora - physiology; Powdery mildew; resistance management; Sensitivity; Spain; sterol biosynthesis inhibitors; Sterols; Sterols - metabolism; Studies; Triadimenol; Spain; Southern Europe; Europe; Spain, Andalucia, Almeria; Spain, Murcia; Spain, Extremadura, Badajoz; Ascomycota; Azole; powdery mildew; Plant pathogen; Mycosis; sterol biosynthesis inhibitors; Pesticides; Cucurbitaceae; fungicide resistance; Sterol synthesis inhibitor; Fungicide; Fungi; Infection; cucurbits; azoles; Dicotyledones; Angiospermae; Population; Spermatophyta; Cross resistance; cross-resistance; Pesticide resistance
• ISSN: 1526-498X; 1526-4998; 1526-4998
• DOI: 10.1002/ps.1948

BACKGROUND: Cucurbit powdery mildew elicited by Podosphaera fusca (Fr.) U Braun & N Shishkoff limits crop production in Spain. Disease control is largely dependent on fungicides such as sterol demethylation inhibitors (DMIs). Fungicide resistance is an increasing problem in this pathogen. To overcome such risk, it is necessary to design rational control programmes based upon knowledge of field resistance. The aim of this study was to investigate the state of DMI sensitivity of Spanish P. fusca populations and provide tools for improved disease management.RESULTS: Using a leaf-disc assay, sensitivity to fenarimol, myclobutanil and triadimenol of 50 isolates of P. fusca was analysed to determine discriminatory concentrations between sensitive and resistant isolates. As no clearly different groups of isolates could be identified, discriminatory concentrations were established on the basis of maximum fungicide field application rate, 100 mg L⁻¹ for the three fungicides tested. Subsequently, a survey of DMI resistance was carried out in different provinces located in the south central area of Spain during the cucurbit growing seasons in 2002, 2003 and 2004. Examination of a collection of 250 isolates revealed that 23% were resistant to fenarimol and 7% to triadimenol, the provinces of Almería, Badajoz and Murcia being the locations with the highest frequencies of resistance. By contrast, no resistance to myclobutanil was found.CONCLUSION: Results show that fenarimol and, to a lesser extent, triadimenol have become less efficient for controlling cucurbit powdery mildew in Spain. These are important observations that should lead to reconsideration of the current disease management programmes. Copyright