Incidence of Fusarium Spp. in Asparagus in Northern Germany: Species Diversity, Virulence and the Relation of Fungus Spread and Asparagus Fly (Platyparea poeciloptera)

摘要

The occurrence of Fusarium crown and root rot was evaluated on 8 selected asparagus fields in Lower Saxony, Germany, during the harvest periods May and June and in autumn 2008 and 2009. The incidence of infection by Fusarium spp. depended on location and season. The peak of Fusarium infection arose during the harvest in June with an average of 64 and 44% of plants infected, in September the infection increased to 100%. The dominant species were F. oxysporum followed by F. proliferatum at an average incidence of 61 and 5%, respectively, during the harvest. In autumn, F. proliferatum was recovered more frequently (71%). On the same fields occurrence of Platyparea poeciloptera was high in both years, but flight intensity was highly variable between fields. An assumed synergistic effect of P. poeciloptera wounding of spears during egg deposition and Fusarium spp. infection and spread was proven under greenhouse conditions. The inoculation was performed on either roots or spears or both roots and spears of six-weeks-old asparagus plants. Plant parts were regularly checked for F. proliferatum infection. No infection with F. proliferatum was detected after inoculation of unwounded spears. Inoculation of wounded spears however resulted in a systemic infection, spreading to the non-inoculated roots. The disease incidence was not significantly different from infections of the roots resulting from root-inoculation only.