Biology and control of black rot of cranberry caused by Ceuthospora lunata shear in Wisconsin.
Schwarz, Michael Richard.
Thesis of Ph.D., The University of Wisconsin - Madison, 1981, 211 pages
1981
บทคัดย่อ
Periodic isolations from plants parts showed that Ceuthospora lunata Shear, casual agent of black rot of cranberry (Vaccinium macrocarpon Ait.), was present throughout the growing season on cranberry and other Ericaceous plants. C. lunata pycnidia were observed sporulating on necrotic cranberry leaves collected in early May through October, and the fungus overwintered as pycnidia in leaf debris.
Cool temperatures (12 - 16 C) and high humidity favored pycnidium production and sporulation in vitro and on necrotic leaves and green fruit. Sporulation was limited on ripe fruit.
Laboratory, growth chamber and field studies indicated that C. lunata was primarily a wound-invading organism. Germination of C. lunata spores on fruit was stimulated in the vicinity of wounds made by puncturing the epidermis. Spores or hyphae could remain viable on the fruit cuticle for six weeks or more and germinate and grow into inner tissues when wounds were made at the site. Black rot developed in wounded fruit at all temperatures (4 - 28 C) and in all varieties tested. In the field, more black rot developed in wounded fruit than in nonwounded controls. Artificially introduced inoculum had no additional impact on the incidence of black rot in these field trials.
Harvest- and rain-water were important media for dissemination of C. lunata spores. Concentrations of up to 206 viable spores/ml were counted in trapped rain water and up to 119 spores/ml were found in flood waters used for wetraking. Black rot developed in wounded berries immersed in harvest water samples but none developed in controls.
Fungicides were effective in inhibiting radial growth and spore germination of C. lunata in vitro, but no significant differences in black rot incidence was detected between treated and nontreated plots in the field. Inoculated cranberries dipped in postharvest fungicides or exposed to acetaldehyde vapor had a significant reduction of black rot.
Two distinct strains of C. lunata differed in pycnidium size, spore size and shape, and colony morphology. Pathogenic differences were not clear-cut. New species designations were not attempted because the type specimens could not be located.
A substantial portion of black rot from New Jersey was caused by Strasseria oxycocci Shear.