Effects of fungicides on in vitro spore germination and mycelial growth of the phytopathogens Leptosphaeria maculans and L. biglobosa (phoma stem canker of oilseed rape)

• Published in: Pest management science 2010-04, Vol.66 (4), p.396-405
• Main Authors: Eckert, Maria R, Rossall, Stephen, Selley, Andrew, Fitt, Bruce DL
• Format: Article
• Language: English
• Subjects: application rate; Ascomycota - drug effects; Ascomycota - growth & development; Ascomycota - physiology; Ascospores; Benomyl; Benzimidazole; Biological and medical sciences; Brassica napus; Brassica rapa - microbiology; Carbendazim; Chemistry, Pharmaceutical; Conidia; Control; crop disease control; Crops; Dose-Response Relationship, Drug; effective dose 50; flusilazole; Foliar applications; food security; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; fungal spores; Fungi; fungicide efficacy; Fungicides; Fungicides, Industrial - pharmacology; Germ tubes; Germination; Germination - drug effects; in vitro studies; Indexing in process; Leptosphaeria; Leptosphaeria biglobosa; Leptosphaeria maculans; microbial growth; Mycelia; mycelium; Mycelium - drug effects; Mycelium - growth & development; Pathogens; Pest control; Pesticides; Phoma; Phoma lingam; Phytopathology. Animal pests. Plant and forest protection; Plant diseases; Plant Diseases - microbiology; plant pathogenic fungi; Rape plants; species differences; Spore germination; Spores, Fungal - drug effects; Spores, Fungal - physiology; Stem canker; Tebuconazole; triazole fungicides
• ISSN: 1526-498X; 1526-4998; 1526-4998
• DOI: 10.1002/ps.1890

BACKGROUND: Phoma stem canker, caused by the coexisting related fungal pathogens Leptosphaeria maculans (Des.) Ces. & de Not and L. biglobosa Shoemaker & H Brun, is a major disease of winter oilseed rape in the UK. Annually, over 90% of UK crops receive at least one foliar application of fungicide, but little is known about the sensitivity of the more damaging L. maculans and the less damaging L. biglobosa to these fungicides. The effects of flusilazole, tebuconazole and Methyl Benzimidazole Carbamate (MBC) fungicides (benomyl and carbendazim) on the germination of ascospores, conidia and germ tube growth of both species were examined. Isolates collected from different oilseed rape crops in England and Wales were assessed for their mycelial growth on fungicide-amended medium, and ED₅₀ values were calculated.RESULTS: Leptosphaeria maculans and L. biglobosa differed in their sensitivity to fungicides. Conidial germination of L. maculans was more sensitive to these fungicides than that of L. biglobosa. Isolates of L. maculans had smaller ED₅₀ values for mycelial growth for all fungicides tested than isolates of L. biglobosa.CONCLUSION: These results suggest that fungicide applications might affect the structure of L. maculans/L. biglobosa populations in UK winter oilseed rape crops.