Management Using Xanthomonas arboricola pv juglandis Dormant Bud Population Sampling Richard P Buchner UC Farm Advisor Tehama County William H Olson UC Farm Advisor Emeritus Butte County ID: 459908
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Walnut Blight Management Using Xanthomonas arboricola pv juglandis Dormant Bud Population Sampling
Richard P. Buchner – UC Farm Advisor, Tehama CountyWilliam H. Olson – UC Farm Advisor Emeritus Butte County Dr. Steven E. Lindow – Plant Pathology UC Berkeley Dr. James E. Adaskaveg – Plant Pathology UC Riverside Cyndi K. Gilles – Research Assistant Tehama CountyRenee Koutsoukis – Research Assistant UC BerkeleySlide2
Walnut Blight infestation in Northern California Xanthomonas arboricola pv juglandisSlide3Slide4
Blight History – Vina VarietyTehama County, California
Location
2011 % pathogen
2011 % Blight
2012 % pathogen
2012 Spray Schedule
2012 %
Blight
South
16
1.49304/16 & 5/23.50Middle231.23104/16 & 5/26.49North62.00164/16 & 5/22.42
2011 Spray Schedule:
6.74 Kg/Ha Kocide
2000 +
2.7 Kg/Ha Pro-Stick
4/12, 4/26 and 5/5
2012 Spray Schedule:
4.49 Kg/Ha Badge
+
2.7 Kg/Ha Manzate
4/16 and 5/2Slide5
Tree #
Rating
Tree #
Rating
69
L
34
M
68
M
33L67L32L66L31M65M
30
M64L29L63H28L62H27L61H26L60H25Replant59H24L58H23M57H22L56H21L55M20054M19L53L18L52L17L51M16Replant50015049M14048L13047M12L46M11045M10L44L9043M8042H7041Replant6040L5L3904L38M3Replant37L2036L1035L
(no nut drop)
(0 to 30 nuts)
(30 to 100 nuts)
(over 100 nuts)
Xaj Histogram for Medium Blight Rating
0.0
1.0
2.0
3.0
4.0
5.0
6.0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Bud #
Log (Cfu/bud)
2012
Vina Walnut in Tehama County, California
(30 to 100 nuts)
10% infested buds
40% infested buds
67% infested buds
5
0% infested budsSlide6
(G) or (A) indicates ground or air applications. (H) indicates half sprays every other row alternating. B=Badge at 4.49 Kg/Ha, M=Manzate at 2.7 Kg/Ha, S=Freeway at 292.30 ml/Ha and Z=Zinc Sulfate 36% at 1.12 Kg/Ha.
2011 % Path-ogen
2011% Blight
2012 % Path-ogen
Vina 2012 Spray Schedule
Butte County, California
2012 % Blight
60
2.60
43
4/2 (A) B,M,S,Z4/9 (GH) B,M,S,Z4/16 (A) B,M,S4/24 (GH) B,M,S,Z5/25 (GH) B,M16.173.5234/2(A) B,M,S4/9 (GH) B,M,S,Z4/16(A) B,M,S4/24(GH) B,M,S,Z
5/25
(GH) B,M.87Slide7
Walnut Blight damage for 14 walnut orchards in Tehama County from 2010 to 2013. Blight damage is increasing in one orchard with a history of high initial inoculum.Slide8
Walnut Blight damage for 15 walnut orchards from 2011 to 2013. Improved spray programs plus a low disease pressure year resulted in much better disease control in 2013.Slide9
Relationship of % buds with pathogen and the associated bud population. Very strong correlation of incidence of bud infestation with average population size of pathogen – disease prediction can be made based on more easily measured incidence of infestation rather than average population size. The lines drawn represent the linear regressions Y=0.0308X + 0.055 (R2=0.967) (2012); and Y=0.0398x + 0.067 (R2=0.626) (2013).Slide10
Relationship between the % buds infested with pathogen and the % walnut blight damage for 30 orchards in Butte and Tehama counties for 2012. The lines drawn represent the linear regression Y=0.218x – 0.28 (R2=0.56); and Y=0.001x + 0.14 (R2=0.001) for orchards in Butte and Tehama counties, respectively.Slide11
Relationship between the % buds infested with pathogen and the % walnut blight damage for 30 orchards in Butte and Tehama counties for 2013. The lines drawn represent the linear regressions Y=0.039x + 0.067 (R2=0.626); and Y=0.032x – 0.096 (R2=0.58) for orchards in Butte and Tehama counties, respectively.Slide12
Walnut Bud Sampling MethodologySample buds in December, January, February, March or early April for late leafing varieties. Buds can be sampled to the time they start to open. Early samples will allow more time to design disease control strategies.Slide13
Select 100 dormant walnut spurs with nice fat terminal buds. Cut off about a 3 inch length. Spurs reachable from the ground are easy to collect and represent a good sample location because bacteria sprinkle down through the tree canopy.Slide14
Walk the entire area collecting a random sample. One or two buds per tree should spread the sample adequately. Deciding how many samples to collect will depend upon experience on an orchard by orchard basis. One sample could easily represent 50 acres if experience suggests reasonable uniformity.Slide15
Save spurs in a paper bag and store in a cool dry place. The paper bag will allow samples to breathe and eliminate condensation. Mail or transport buds to a lab. The lab will select a 30 terminal bud subsample to plate on agar and save the remaining buds as a backup sample.Slide16
Walnut orchards can be highly variable. Try to achieve as representative sample as possible.Slide17
In California, samples can be analyzed at the California Seed and Plant Lab. www.calspl.com 916-655-1581Slide18
Incidence of populations of X. juglandis on walnut buds sampled following harvest on 12/1/10. This is a histogram typical for a low population sample. Notice that over 25 buds had zero pathogen.Slide19
Incidence of populations of X. juglandis on walnut buds sampled following harvest on 12/1/10. This is a histogram for a high population sample. Notice that only 8 buds had no detectable pathogen and most of the buds were in the ten to the fourth (10,000 colony forming units) or more range. This would be an example of a high risk orchard.Slide20
Additional Informationcetehama@ucanr.edu (Buchner website)walnutresearch.ucanr.edu (California Walnut Research Reports)www.calspl.com
(California Seed and Plant Lab)Thank you