Plant Pathology (1997) 46, 680-693

M.L. Sutherland and C.M. Brasier (1997)
A comparison of thirteen d-factors as potential biological control agents of Ophiostoma novo-ulmi
Plant Pathology 46 (5), 680-693
Abstract: Thirteen d-factors varied in their ability to reduce the conidial viability of healthy EAN or NAN race isolates of the Dutch elm disease fungus Ophiostoma novo-ulmi in vitro, causing mild (c. 7-30%), moderate (c. 60-75%) or severe (c. 80-90%) reductions. The influence of the same d-factors on the persistence of O. novo-ulmi isolates in the natural infection court, and on xylem infection of the susceptible Ulmus procera, was investigated under field conditions in artificial feeding grooves. Both persistence and xylem infection levels were consistently reduced. The effects again varied considerably with different d-factors, which could be ranked within a continuum, ranging from a minimal effect exerted by d¹ and a mild effect by d⁴; to those with a moderate effect, d⁵, d⁶, d⁷, d⁸, d¹⁰, d¹¹, d¹² and d¹³; and those with a severe effect, d², d³ and d⁹. On the moderately resistant U. x hollandica cv. 'Commelin', the severe d-factors d² and d⁹ again markedly reduced persistence of O. novo-ulmi in the feeding groove and increased the spore threshold for xylem infection from c. 5000 with a healthy isolate to c. 50 000-500 000 spores. When healthy EAN isolate P114 was infected with a range of different d-factors, xylem infection frequency following inoculation of U. procera with 10 000 spores was positively correlated with both the level of conidial viability and germ tube vigour in vitro, and hence was negatively correlated with the severity of the d-factors involved. The potential of d-factors for the biological control of Dutch elm disease is discussed.
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Database assignments for author(s): Clive M. Brasier

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ophiostoma novo-ulmi	Elm (Ulmus)	United Kingdom