Identification, Pathogenicity and Comparative Virulence of Fusarium spp. Associated with Diseased Euphorbia spp. in Europe

Abstract

Abstract:Fusarium spp. isolated from diseased Euphorbia spp. in Europe were assessed for pathogenicity to North American leafy spurge (Euphorbia esula/virgata. Of the nine strains of Fusarium spp. isolated either from diseased E. stepposa or E. virgata in the Caucasus region of Russia and E. esula/virgata in southern France, respectively, all were pathogenic to leafy spurge. There were significant differences in virulence among strains. Four strains, including the two most virulent, were identified as F. oxysporum. Four of the five other strains were identified as F. solani and one was identified as F. proliferatum. Three of the four most virulent strains to leafy were isolated from E. stepposa. The most virulent strain was associated with root damage caused by insect biological control agents, similar to a previous study on domestic strains of Fusarium spp. pathogenic to leafy spurge. Two strains identified as F. solani were vegetatively compatible. It was concluded that further screening of a larger set of strains of foreign Fusarium spp. under quarantine conditions stateside or in limited overseas facilities is justified and promising.

Effects of European and U.S. Strains of Fusarium spp. Pathogenic to Leafy Spurge on North American Grasses and Cultivated Species

“…Neither of the two most virulent European strains, 94f-5 and 94f-37, both previously identified as F. oxysporum (Caesar et al, 1998), caused apparent disease or reduced dry weight of any of 12 cultivated species on which they were tested (Table 3). No European strain caused disease within 3 weeks after inoculation by root-dip.…”

“…The strains assessed in the present study have been described previously (Caesar, 1996;Caesar et al, 1998). The host ranges of the strains were assessed on 12 North American grass species listed in Table 1.…”

“…are also found frequently in Europe (Caesar et al, 1998), where the plant is widespread in small stands and is typically infested with one or more insects, including root-attacking species. Often the most virulent pathogen strains are associated with diseased roots fed upon by insects (Caesar, 1996;Caesar et al, 1998). Strains of three Fusarium species, F. oxysporum Sclechtend.…”

“…Strains of three Fusarium species, F. oxysporum Sclechtend. : Fr., F. solani (Mart) Sacc., and F. proliferatum (T. Matsushima) Nirenberg were highly virulent to leafy spurge in greenhouse tests (Caesar, 1996;Caesar et al, 1998). Field applications of a formulated strain of F. oxysporum have reduced stand density by as much as 30% over a single season (Caesar, unpublished).…”

Influence of plant phenostage and ploidy level on oviposition and feeding of two specialist herbivores of spotted knapweed, Centaurea stoebe

“…Various measures have been implemented in North America to control the spread of C. stoebe, including the use of herbicides Jacobs et al, 2000), the alteration of nutrient availability (Herron et al, 2001) and the use of biological control agents (Müller-Schärer and Schroeder, 1993;Story and Piper, 2001;Caesar et al, 2002;Wooley et al, 2011). Insect biological control agents have received particular attention with 13 species released since 1970 (Story and Piper, 2001;Knochel and Seastedt, 2010).…”