The mechanics of bacterial cluster formation on plant leaf ...
Understanding and Managing Pecan Bacterial Leaf...
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Understanding and Managing Pecan Bacterial Leaf Scorch Southeastern Pecan Growers Association Convention Destin, Florida • February 26-27, 2016 Rebecca A. Melanson, Extension Plant Pathologist Central MS Research and Extension Center • Raymond, MS
Transcript of Understanding and Managing Pecan Bacterial Leaf...
Understanding and ManagingPecan Bacterial Leaf Scorch
Southeastern Pecan Growers Association ConventionDestin, Florida • February 26-27, 2016
Rebecca A. Melanson, Extension Plant PathologistCentral MS Research and Extension Center • Raymond, MS
A Bit of History
• Disease first recognized in 1972
• Identified as a bacterial disease and named pecan bacterial leaf scorch (PBLS) in 2000• Xylella fastidiosa subsp.
multiplex (2012)• Lives in the water-conducting
tissues (xylem) of the plantPBLS in ‘Cape Fear’ pecan.
PBLS Symptoms
Late-stage PBLS symptoms. ‘Early’-stage PBLS symptoms.
PBLS Symptoms
PBLS in a mature tree.PBLS in a young grafted tree.
MorelandNavahoNacono*Oconee*Pawnee*RomeSchley
Cultivar Susceptibility
*BartonCaddo
*Cape Fear Candy
Cherokee*CheyenneDesirable
ElliottFarleyForkertJacksonKiowaMahan
Melrose
ShoshoniStuart
*SumnerWoodman
Natives/seedlings
NO RESISTANT CULTIVARS HAVE BEEN IDENTIFIED.
Reference: Sanderlin, 2005, Plant Disease 89:446-449.
*Highly susceptible cultivars.
Time Period
% Leaflet Defoliation
% Reduced Kernel Weight
% Reduced Nut Weight
Year 1 67 19 29Year 2 66 16 32Year 3 41 14 20
Average 58 16.3 27
Age of Trees % Less Diameter % Less Height4 Years Old 43 409 Years Old 52 N/A
Effect of PBLS on Yield and Tree Growth
Yield
Tree Growth
References: Sanderlin and Heyderich-Alger, 2003, Plant Disease 87(3):259-262.; Sanderlin, unpublished
Graft Transmission in Pecan
PBLS in new growth from infected scion.
• Infected scions– 21% transmission rate
• Infected rootstocks– 85% transmission rate
References: Sanderlin and Melanson, 2008, Plant Disease 92:1124-1126.; Sanderlin and Melanson, 2006, HortScience 41(6):1455-1456.
Prepared scions for storage.
Submerged scions in hot water. Grafted to non-infected rootstock.
Identified PBLS-infected limbs.
Hot-water Treatment of Scions
Bundled scions with a weight.
Treatment• 115ºF water for 30 min• Room temperature
water for 1-2 minCompletely submerge!
The link to the publication “Procedure for Hot Water Treatment of Pecan Scion Wood” can be found at the end of this presentation.
Two-Year Totals
# of ScionsTested
% GraftSuccess
# of Treeswith PBLS Symptoms
# of X. fastidiosa-
InfectedTrees
Hot-waterTreated Scions
165 84.8 2 1
Non-treatedScions 105 84.7 18 19
0.7
21.3
0
20
40
60
80
100
Hot-water-treatedscions
Non-treated scions
% G
raft-
trans
miss
ion
of X
. fas
tidio
sa
At a 21% graft-transmission rate, 29 of the 140 hot-water-treated scions
should have been infected. **97% EFFECTIVE**
Hot-water Treatment of Scions
Reference: Sanderlin and Melanson, 2008, Plant Disease 92:1124-1126.
PBLS Spread in a Mature Orchard• Orchard location:
LSU AgCenter Pecan Research-Extension Station, Shreveport, Louisiana
• Planting date: 1986 or 1987
• Composition:– 3 cultivars and non-
grafted trees– 5 rootstocks
Year Number of Diseased Trees/Number of Trees in Orchard (% Infected Trees)
2001 5/410 (1.2%)2002 12/410 (2.9%)2003 17/409 (4.2%)2004 33/390 (8.5%)2005 63/390 (16.2%)2006 91/390 (23.3%)
An increase in the number of PBLS-infected trees was observed in all cultivars and in most non-grafted trees.
However, the greatest increase in the number of infected trees occurred in cultivar Cape Fear, the cultivar in the
orchard with the highest susceptibility.
Insect Transmission in Pecan
Fed captured insects on infected pecan tissue and then caged them onto Cape Fear pecan seedlings.
Collected potential vectors –xylem-feeding insects
(spittlebugs and sharpshooters).
• Percent transmission varied from 2% – 100% depending on the insect species
Insect Transmission in Pecan
Lateral-lined sharpshooter Johnsongrass sharpshooter
Diamond-backed spittlebug Glassy-winged sharpshooter
Pecan spittlebug (adult)
Photos by: S. Gil Photo by: R. Melanson
2 – 11.4%
100% 19.6%
16.7% 4%
Reference: Sanderlin and Melanson, 2010, Plant Disease 94(4):465-470.
Dr. R. S. Sanderlin at the LSU AgCenterPecan Research-Extension Station in
Shreveport, LA, has monitored five pecan orchards in Louisiana for the presence of
known and potential vectors of Xylella fastidiosa using yellow sticky traps.
Data indicated that the greatest number of known and potential vectors were present in
orchards from May through August.
Monitoring Pecan Orchards for Vectors*
Orchard locations:
*Known and potential vectors
Subspecies of Xylella fastidiosa• Subspecies fastidiosa (2004)
– Almond, grapevine• Subspecies multiplex (2004)
– Almond, peach, oak, pecan• Subspecies pauca* (2004)
– Citrus, coffee• Subspecies sandyi (2005)
– Oleander• Subspecies tashke (2009)
– Chitalpa
Pierce’s diseaseA. H. Purcell, Univ. CA - Berkeley, Bugwood.org
Citrus variegated chlorosis*A. H. Purcell, Univ. CA, Bugwood.org
Bacterial leaf scorch in pin oakJ. Hartman, Univ. KY, Bugwood.org
Bacterial leaf scorch in sycamoreT. D. Leininger, USDA Forest Service, Bugwood.org*Not currently present in the U.S.
• FOCUSED ON PREVENTION!• Plant non-infected trees• Use non-infected rootstock• Collect scion wood from non-infected trees• Hot-water treatment of scions
• Monitor vectors in orchards and apply insecticides during peak trapping periods or at first appearance (?)
• Avoid planting/remove plants near orchards that attract vectors OR manage vectors on those plants (?)
• Branch or tree removal (?)
Management of PBLS
Thank you for your attention!
• Rebecca A. MelansonExtension Plant Pathologist Central Mississippi Research and Extension CenterMississippi State UniversityPhone: (601) 857-2284Email: [email protected]
• R. S. SanderlinResearch/Extension Plant PathologistLSU AgCenter Pecan Research-Extension StationLouisiana State UniversityEmail: [email protected]
Photo by MSU Extension
The research discussed in this presentation was conducted by R. A. Melanson and R. S. Sanderlin at the LSU AgCenterPecan Research-Extension Station or at Louisiana State
University. Unless otherwise specified, photographs were taken by R. A. Melanson or R. S. Sanderlin.
• Articles:– Pecan Bacterial Leaf Scorch Cultivar Susceptibility and Pathogen Transmission– Pecan Bacterial Leaf Scorch: A New Look at an Old Problem– Procedure for Hot Water Treatment of Pecan Scion Wood
• Additional photos of PBLS (search ‘Xylella fastidiosa and pecan’)– www.ipmimages.org/
Additional Resources
• Melanson, R. A. and Sanderlin, R.S. 2015. Hot-water treatment of pecan scions as a means of phytosanitation to reduce the potential introduction of Xylella fastidiosa, the causal agent of pecan bacterial leaf scorch, into orchards and new geographic regions. Acta Horticulturae 1070:201-209.
• Melanson, R. A., Sanderlin, R. S., McTaggart, A. R. and Ham, J. H. 2012. A systematic study reveals that Xylella fastidiosa strains from pecan are part of X. fastidiosa subsp. multiplex. Plant Disease 96:1123-1134.
• Li, B., Sanderlin, R. S., Melanson, R. A., and Yu, Q. 2011. Spatial analysis of a plant disease in a non-uniform crop: a Monte Carlo approach. Journal of Applied Statistics 38(1):175-182.
• Sanderlin, R. S. and Melanson, R. A. 2010. Insect transmission of Xylella fastidiosa to pecan. Plant Disease 94(4):465-470.• Sanderlin, R. S., Li, B., Melanson, R. A., and Gil, S. 2009. Spread of Xylella fastidiosa in a pecan orchard and presence of potential vectors in
orchards. Phytopathology 99:S114. (abstract)• Sanderlin, R. S. and Melanson, R. A. 2008. Reduction of Xylella fastidiosa transmission through pecan scion wood by hot-water treatment. Plant
Disease 92:1124-1126.• Sanderlin, R. S. and Melanson, R. A. 2006. Transmission of Xylella fastidiosa through pecan rootstock. HortScience 41(6):1455-1456.• Sanderlin, R. S. 2005. Cultivar and seedling susceptibility to pecan bacterial leaf scorch caused by Xylella fastidiosa and graft transmission of the
pathogen. Plant Disease 89:446-449.• Sanderlin, R. S. and Heyderich-Alger, K. I. 2003. Effects of pecan bacterial leaf scorch on growth and yield components of cultivar Cape Fear. Plant
Disease 87(3):259-262.• Sanderlin, R. S. and Heyderich-Alger, K. I. 2000. Evidence that Xylella fastidiosa can cause leaf scorch disease of pecan. Plant Disease 84 (12):
1282-1286.• Sanderlin, R. S. 1998. Evidence that Xylella fastidiosa is associated with pecan fungal leaf scorch. Plant Disease 82:264.
PBLS Research Publications
