Black spot of roses, caused by the fungus Marssonina rosae (teleomorph = Diplocarpon rosae ), is the most important and damaging disease of roses in landscapes worldwide. The pathogen causes round to irregular coal black spots with fringed
To determine the efficacy of cyproconazole for control of black spot [Marssonina rosae (Lib.) Lind] when applied as a drench, treatments of 0, 32.5, 65, 97.5 and 130 g a.i./ha were initiated 9 May 1994 on individual Rosa `Peace' plants in a randomized complete-block design. Treatments were applied once per month until 18 Oct. 1994. Data were taken in July, Sept., and Nov. 1994 when separate disease and defoliation ratings were assigned. By July, the controls were heavily infected; the higher treatment rates resulted in significant control. By September, the disease and defoliation ratings exhibited a linear response with cyproconazole rate, with the highest treatment rate giving the best control. The relationship between disease and defoliation ratings and treatment rate remained the same in November, although there was increased disease incidence overall. No phytotoxicity was observed. These results indicate that soil applied treatments of cyproconazole can control black spot effectively on roses.
Forty-five rose genotypes including modem cultivars and rose species were evaluated in a field trial for resistance to black spot caused by Marssonina rosae. The trial was designed as a randomized block with four replications at two sites. The plots were planted at College Station (East Central Texas) and Overton (Northeast Texas). Ratings were done for the percentage of leatlets with black spot lesions and for leaf defoliation. These ratings were taken four times during the growing season from May to October 1993. Preliminary results indicate a high degree of resistance in the ten species studied, Modem cultivars were equally divided into moderate resistance, low resistance, and susceptible with only four showing high resistance. Disease pressure was higher and occurred earlier in the season at the Overton site. Disease pressure was highest at both sites in late spring and again in fall. Pressure was lowest in August after a prolonged period without rain. Introduction during the growing season of a previously unseen race of the pathogen was observed by the performance of the cultivar Sunbright.
The fungus Diplocarpon rosae (anamorph = Marssonina rosae Lind.) is the causal organism of rose black spot, which is the most damaging disease of rose worldwide ( Dobbs, 1984 ). Symptoms include lesions on leaves and stems as well as frequent
pathogen Marssonina rosae estimated by RAPD Intl. J. Hort. Sci. 12 63 67 Whitaker, V.M. Bradeen, J.M. Debener, T. Biber, A. Hokanson, S.C. 2010a Rdr3 , a novel locus conferring black spot disease resistance in tetraploid rose: Genetic analysis, LRR
cultivars resistant to the common rose diseases ( Byrne, 2015 ; Debener and Byrne, 2014 ). Black spot, the most important disease affecting garden roses globally, is caused by the fungus D. rosae Wolf ( Marssonina rosae anamorph) ( Nauta and Spooner
Carlson-Nilsson, B.U. Davidson, C.G. 2006 Variation in resistance to Marssonina rosae (Lib.) Died. among different Rosa L. cultivars and species including three dogrose species ( Rosa sect. Caninae ) Sci. Hort. 109 353 360
). Once established, black spot can be difficult to manage ( Gachomo et al. 2009 ). Black spot disease of rose is caused by the hemibiotrophic fungal pathogen Diplocarpon rosae , the teleomorph stage, and Marssonina rosae , the anamorph stage ( Bowen
. < http://www.home-run-rose.com/ > Wenefrida, I. Spencer, J.A. 1993 Marssonina rosae variants in Mississippi and their virulence on selected rose cultivars Plant Dis. 77 246 248 10.1094/PD-77-0246 Whitaker, V.M. Hokanson, S.C. Bradeen, J. 2007
sulfur-containing compound derived from garlic Appl. Environ. Microbiol. 62 4238 4242 10.1128/aem.62.11.4238-4242.1996 Quarnstrom, K. 1992 Treatment of blackspot ( Marssonina rosae ) on outdoor roses Vaxtskyddsnotiser 56 21 25 Raghavaiah, G. Jayaramaiah