Authors
R. B.
Nesbitt
,
Nesbitt and Associates Horticulture Consultants, 1019 E. Walnut Ave., Orange, CA 92667
;
T. E.
Tidwell
,
California Department of Food and Agriculture Plant Pest Diagnostics Center, 3294 Meadowview Rd., Sacramento 95832
; and
R. J.
Stipes
and
G. J.
Griffin
,
Virginia Polytechnic Institute and State University, 410 Price Hall, Blacksburg 24061-0331
A Fusarium sp. was isolated from a 12-year-old Silk Tree (Albizia julibrissin) in a residential area of Redlands, CA. The scaffold branches and trunk exhibited gummosis, the sap oozing from fissures or intact bark. Internally the wood exhibited brown to black broad streaks of discoloration from the scaffold branches down into lateral roots below the root crown, similar to symptoms observed in Virginia (2). Wilted and dried foliage remained on the scaffold branches. Two-week-old cultures of the isolate grown on Komada (1) and acidified potato dextrose agar media developed short conidiophores, macroconidia, and colony morphology typical of Fusarium oxysporum. To complete Koch's postulates, 1-month-old seedlings were root-dip inoculated with a water suspension of macro- and microconidia (106 per ml). Two weeks after inoculation, typical Fusarium wilt symptoms developed in all inoculated seedlings. The fungus was reisolated from symptomatic seedlings. This is the first report of mimosa wilt disease in California. The disease has the potential to adversely impact California's nursery and landscape industry.
References: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (2) R. J. Stipes and P. M. Phipps. Phytopathology 65:188, 1975.
