Lea Hiltunen

The potential for the biological control of basal rot of Narcissus by Streptomyces sp.

Abstract Glasshouse experiments were conducted over 2 years to study the control of basal rot of Narcissus by a biological product based on a Streptomyces sp. In year 1, 88% of untreated bulbs of the susceptible cv. Golden Harvest were infected and artificial inoculation did not increase disease incidence. The Streptomyces sp. dip (0.1%) did not control the disease. In Year 2, natural infection of Golden Harvest was 15% and artificial inoculation increased infection of untreated bulbs to 53%. The Streptomyces dip (0.01%) supplemented with spray applications controlled basal rot as effectively as thiabendazole hypochlorite. Natural infection of cv. Carlton was 19–20% and artificial inoculation increased the percentages of infected bulbs to 64% (Year 1) and 71 % (Year 2). In Year 1, the Streptomyces dip (0.1 %) reduced disease for cv. Carlton by 24%. In Year 2, all Streptomyces treatments reduced the disease incidence in this cultivar. The combination of 0.01% dip and spray was most effective, reducing infection to 18.7%. Basal rot resulting from natural or artificial infection of the resistant cv. Ice Follies was too low to determine the effectiveness of treatments. The Streptomyces sp. did not control natural infection originating from bulbs. The results suggest that the Streptomyces sp. has potential as a component of an integrated control strategy for basal rot.