250 DeStefano et al.: Effect of Growth Regulator Paclobutrazol ments are needed to evaluate the effect of higher rates of PBZ on mature trees as well as their ability to control X. fastidiosa. Repeated treatments as well as methods and timing of deliv- ery should also be investigated. Acknowledgments. We thank the University of Maryland, Depart- ment of Plant Science and Landscape Architecture for partial sup- port of this project through a Research Assistantship to the senior author. This work was completed in partial fulfillment of a Master of Science degree. LITERATURE CITED Burden, R.S., G.A. Carter, T. Clark, D.T. Cooke, S.J. Croker, A.H.B. Deas, P. Hedden, C.S. James, and J.R. Lenton. 1987. Comparative activity of the enantiomers of tri- adimenol and paclobutrazol as inhibitors of fungal growth and plant sterol and gibberellin biosynthesis. Pesticide Science 21:253–267. Davis, M.J., W.J. French, and N.W. Schaad. 1981. Axenic culture of the bacteria associated with phony disease of peach and plum leaf scald. Current Microbiology 6:309–314. Davis, M.J., A.H. Purcell, and S.V. Thomson. 1978. Pierce’s disease of grapevines. Isolation of causal bacterium. For- est Science 199:75–77. Feeley, J.C., R.J. Gibson, G.W. Gorman, N.C. Landford, J.K. Rasheed, D.C. Mackel, and W.B. Baine. 1979. Charcoal- yeast extract agar: Primary isolation medium for Le- gionella pneumophila. Journal of Clinical Microbiology 10:437–441. Figure 3. Growth curve of Xylella fastidiosa isolate elm (left) and grape (right) in periwinkle wilt (PW) broth supplemented with chemical treatments of oxytetracy- cline (antibiotic) and paclobutrazol (PBZ) measured over 5 days. Colony-forming units (CFUs) were determined by dilution plating. Means and associated standard errors are plotted. hosts, it may not be desirable to separate the enantiomers of the diastereomer for treatment of X. fastidiosa. It is possible that a concentration of the racemic mixture could be devised that restricts bacterial growth as well as provide beneficial physiological changes to the tree. This would prove to be the ideal circumstance for use of the chemical. However, devis- ing the most effective ratio and concentration of enantiomers could be complicated by a possible species-specific treatment response to PBZ and efficacy of the treatment may be de- pendent on the distribution, titer, and strain of X. fastidiosa being treated. This study suggests that PBZ has a direct effect on growth of X. fastidiosa and that treatments with high levels of PBZ could provide a potential treatment. However, field experi- ©2007 International Society of Arboriculture Fletcher, R.A., and G. Hofstra. 1986. Comparative fungitoxic and plant growth regulating properties of triazole deriva- tives. Plant & Cell Physiology 27:367–371. Frakulli, F., and D.G. Voyiatzis. 1999. The growth retardants paclobutrazol and triapenthenol affect water relations and increase drought resistance in olive. Acta Horticulturae 474:427–430. Hearon, S.S., J.L. Sherald, and S.J. Kostka. 1980. Association of xylem-limited bacteria with elm, sycamore, and oak leaf scorch. Canadian Journal of Botany 58:1986–1993. Hopkins, D.L., and W.C. Alderz. 1988. Natural hosts of Xy- lella fastidiosa in Florida. Plant Disease 72:429–431. Hopkins, D.L., H.H. Mollenhauer, and W.J. French. 1973. Occurrence of a rickettsialike bacterium in the xylem of peach with phony disease. Phytopathology 63:1422– 1423. Jacobs, K.A., and L.C. Berg. 2000. Inhibition of fungal pathogens of woody plants by the plant growth regulator paclobutrazol. Pest Management Science 56:407–412. Kostka, S.J., T.A. Tattar, and J.L. Sherald. 1985. Suppression of bacterial leaf scorch in American elm through oxytet- racycline microinjection. Journal of Arboriculture 11: 54–58.
July 2007
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
