Helping the immune system of Knock Out roses

13 years ago

Title: Effect of acibenzolar-S-methyl on bacterial leaf spot of shrub roses caused by a Xanthomonas sp.

Author: Vallad, GE

Published in: Phytopathology [Phytopathology]. Vol. 100, no. 6, suppl. 1, p. S177. Jun 2010.

Abstract: "A bacterial leaf spot was recently identified on shrub rose varieties 'Knockout' and 'Double Knockout' caused by a Xanthomonas sp. and can be problematic during vegetative propagation and nursery production. Acibenzolar-S-methyl, the active ingredient of Actigard (Syngenta, Greensboro, NC), is an elicitor of plant defenses that has demonstrated efficacy in the control of several bacterial diseases of vegetable crops. Greenhouse and nursery trials were established to test the effect of Actigard on the severity of bacterial leaf spot on 'Knockout' and 'Double knockout' roses. While lower rates of 0.25 to 0.5 oz of Actigard per 100 gallons were effective at reducing disease severity on potted roses and liners, higher rates of 0.75 to 1.0 oz gave the best results. Multiple applications of Actigard (1.0 oz/100 gal) prior to disease development improved bacterial leaf spot control over single applications. Results demonstrate the potential to use Actigard for disease management on ornamental and nursery species."

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Title: Initial characterization of a Xanthomonas sp. causing bacterial spot of shrub rose (Rosa spp.)

Authors: Vallad, G : Summers, C : Adkison, H : Margenthaler, E

Published in: Phytopathology [Phytopathology]. Vol. 100, no. 6, suppl. 1, p. S129. Jun 2010.

Abstract: A severe bacterial spot of shrub rose (Rosa spp.) caused by a xanthomonad was observed during summer production in Florida. Foliar symptoms consisted of small black lesions with defined margins that were fairly vein delimited and often located along leaf margins. Based on fatty acid composition and 16S rRNA sequence, the strain was most closely related to several pathovars of Xanthomonas axonopodis. The 16S-23S rRNA intergenic spacer (ITS) and flanking portions of the 16S and 23S rRNA genes were sequenced and compared among three rose strains and those of several characterized strains of X. citrumelo, X. euvesicatoria, X. dieffenbachiae, X. manihotis, and X. perforans. Sequence identity within the nearly 2 kb region was greater than 98.3% among all strains with 100% identity among the rose strains. The rose strains exhibited 99.9% identity with X. perforans. Phylogenetic analyses of the ITS region consistently grouped rose strains closest to X. perforans. Rose strains caused few symptoms when infiltrated at 10 super(6) cfu/ml into leaves of citrus, tomato, pepper, or several members of the Euphorbiaceae or Araceae. However, strains were clearly pathogenic on rose and another Rosaceae, Indian Hawthorne (Rhaphiolepis indica). Results suggest that the rose strains may represent a new species or subspecies of Xanthomonas. Further characterization of rose strains through multi-locus sequence typing and host testing is in progress. This is the first pathogenic Xanthomonas sp. associated with rose."

I will not post the second link as long links cause formating problems. Use Google Scholar to find the link.

Here is a link that might be useful: link for first article above, use Google Scholar to find the second

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Comments (2)

Tom
13 years ago
last modified: 9 years ago
Okay, Henry, you will need to do a little translating. Is Actigard on the market? There is a new strain of bacteria on these roses?
henry_kuska
Original Author
13 years ago
last modified: 9 years ago
I recommend asking your local nursery if it can be ordered. Unfortunately, often agricultural items are often sold in large lots only. If this is the case here, you may be able to get other Florida rose growers to split a shipment with you (rose clubs sometimes do this).

In the past one could often get a small amount free as a test sample, either from the manufacture or a local university. However, it is my impression that government restrictions have pretty well eliminated such practices.

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From a quick scan of Google articles, it sounds like xanthomonas perforans is common among tomatoes in Florida.

Here is a link that might be useful: Florida link
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Helping the immune system of Knock Out roses

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Tom

henry_kuska
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Helping the immune system of Knock Out roses

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Tom

henry_kuskaOriginal Author

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henry_kuska
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