Material Efficacy Screening Air Blast Sprayer and Hand

WALNUT
BLIGHT CONTROL
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MATERIAL
EFFICACY
AIR BLAST SPRAYER AND HAND-GUN
SCREENING
TRIAL
Bill Olson, Milt Schroth
1989
ABSTRACT
Champ at 1 2/3 gal./acre and Kocide 101 at 8 lbs./acre were
evaluated for their ability to control walnut blight in 1989.
The materials were applied 5 times during April and May by an
orchard sprayer. Incidence of walnut blight in the untreated
trees was at 38% while both materials reduced the walnut blight
level down to 3 percent. Both materials resulted in some but not
serious phytotoxicity. In a handgun trial Kocide 101 + "xl";
Kocide 101 + "x2"; and yeast treatments provided the same level
of control of walnut blight than did Kocide alone.
OBJECTIVE
A.
Air Blast Sprayer Trial
1.
Evaluate Kocide 101 and Champ Flowable
control in replicated trial.
2.
To determine
the effect of Kocide
for walnut
101 and Champ
blight
Flowable
sprays on the occurrence of Xanthomonas iuqlandis in
walnut buds.
3.
To detect the presence of copper resistant strains of ~
iuqlandis in Kocide- and Champ-treatedwalnut buds.
B.
Small Handgun
Trial
1.
Evaluate Kocide 101, Champ Flowable, "enhanced" Kocide
101 and a biological treatment for walnut blight control
in a replicated trial.
2.
To monitor the presence of Xanthomonas iuqlandis in
untreated dormant vegetative walnut buds, expanding
vegetative bud tissues, and newly-formed vegetative buds.
3.
To determine the effect of fixed copper, enhanced fixed
copper, and biological treatments on th~ occurrence of ~
iuqlandis in walnut buds.
4.
To determine the prevalence of copper resistant strains
of ~ iuqlandis in treated and untreated walnut buds.
5.
To examine
walnut
buds
for the presence
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of dominant
phenotypic groups of microorganisms that may be antagonistic to ~ ;uqlandis.
PROCEDURE
A.
Air Blast Sprayer Trial
Establish a trial in an Ashley walnut orchard replicated 10
times and treated with one of two materials 5 times in April
and May by air blast sprayer. The materials were Champ at 1
2/3 gal/acre or Kocide 101 at 8 lbs./acre. Evaluate treatments for walnut blight incidence and rate trees for phytotoxicity in June 1989. Nut blight evaluation was based on
any blight strike on 50 nuts per replicate located about 6
feet off the ground and 50 nuts per replicate located 15 feet
off the ground.
Leaf phytotoxicity based on 50 leaves per
replicate and categorized as being clean, bronzed or burnt.
Bud evaluation: Ten shoot terminals were pruned on June 5,
1989 from each of five randomly selected trees in each sampling row. One newly-formed vegetative bud was excised from
each shoot in the laboratory. Excised buds from each tree
were combined to yield composite samples of 10 buds for each
sampled tree. The composite samples were then individually
weighed and macerated in 10 ml of sterile phosphate buffer
solution.
Ten-fold serial dilutions of the macerate were
prepared and 0.1 ml aliquots of the 10-2 and 10-3 dilutions
were plated onto Blue Starch medium. The plates were incubated for 4 days at 29 C, after which colonies of ~ juqlandis were counted. Three pathogen colonies from each positive
sample were then transferred to CYE medium containing 20 or
40 ppm copper sulfate, incubated again, and evaluated for
growth.
B.
Small Handgun Trial
Establish a 5 replicate hand-gun trial in an Ashley walnut
orchard tested 4 times with Champ, Kocide, yeast, Kocide +
xl' or Kocide + x2 and evaluate for incidence of walnut
blight on nuts and leaves and phytotoxicity.
Blighted nut
evaluations based on all nuts per replicate with or without
any blight strikes. Leaf blight and leaf phytotoxicity based
on 25 leaves per replicate.
Bud evaluation: Tissue samples were collected for assay on
April 4 (prior to first spray), April 24 (after the first
spray) and May 31 (after the third spray). Dormant vegetative buds were assayed at the first sampli~g date, expanding
vegetative bud tissues on the second date, and newly-formed
vegetative buds on the final sampling date. At each sampling, the terminal 6 inches of 10 randomly selected shoots
were pruned from each replication (limb). Single buds from
each shoot were selected for assay in the laboratory. Control bud samples were processed individually (50 buds per
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sampling date), while buds from treated plots were combined
for each replication (5 composite samples of 10 buds each for
every treatment). Control buds were individually weighed and
macerated in 5 ml phosphate buffer solution. Composite bud
samples from treated plots were weighed and macerated in 10
ml of phosphate buffer.
Ten-fold serial dilutions of the
macerate were made and plated on Blue Starch (BS), Casetone
Yeast Extract (CYE), King's B (KB), and CYE medium amended
with 20 and 40 ppm copper sulfate.
Medium
Dilutions
Plated
BS
CYE
KB
CYE + 20 ppm CuS04
CYE + 40 ppm CuS04
The plates were incubated at 29 C for three to four days and
colonies were counted.
Bacterial or yeast colonies on KB and
CYE were also classed and quantified based on morphological
features.
Two or three x. iuqlandis
colonies
from each
positive sample were transferred
from BS to CYE plus copper
sulfate, incubated for 3 days and rated for growth to determine copper resistance.
RESULTS
A.
Air Blast Sprayer Trial
Champ at 1 2/3 gal./acre and Kocide 101 at 8 lbs./acre gave
good control of walnut blight with only slight phytotoxicity
(See Table).
Four of the five composite bud samples from the Kocidetreated block had detectable populations of ~ iuqlandis,
while only two of five samples from the Champ-treated block
tested positively for the pathogen.
None of the ~
iuqlandis isolates grew on CYE amended with 20
or 40 ppm copper sulfate, indicating X. iuqlandis was not
resistant
B.
to copper.
Small Hand-gun
Trial
Kocide + xl; Kocide + x2 and the yeast treatments gave equal
control of walnut blight than did Kocide alone (See Table 1).
Due to the unavailability of Champ at the first spray timing,
it was only applied 3 times and this may ~xplain why it did
not perform quite as well as the other materials.
Bud
evaluation:
See following
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table.
Number of individual control buds and composite (treated) bud
samples with detectable populations of ~ iuqlandis from the
1989 Chico hand-sprayed trial.
Number Of Samples With
.
~
iuqlandis
Sampling Date
Previous Season Buds
Treatment
1.
Control
2.
Kocide 101
Kocide 101 + Xl
Kocide 101 + X2
Yeast
Champ Flowable
3.
4.
5.
6.
New Buds
4 Apr
24 Apr
31 May
2/50*
(1/5)**
0/5***
1/5
0/5
0/5
-
2/50
(2/5)
1/5
1/5
1/5
3/5
16/50
(5/5)
3/5
0/5
1/5
1/5
2/5
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*Number of individual control buds with detectable populations of ~ iuqlandis in a total of 50 buds
**Number of control replications with detectable ~ iuqlandis
populations
***Number of composite bud samples (replications) with detectable ~ iuqlandis populations in total of 5 samples per
treatment
Only three copper resistant (20 ppm) isolates of ~ juqlandis
were detected during this trial. Two isolates were from the
control plots and one from the yeast-treated plots.
No
copper tolerant strains were identified from the coppertreated plots.
No phenotypic group or groups predominated among non-walnut
blight organisms isolated on KB and CYE. The buds appeared
to be colonzied by a diverse group of bacteria and some
yeasts.
CONCLUSION
Champ at the rate used was equal to Kocide 101 in the air blast
spray trial. Different rates would be expected to give different
results. The poorer control with Champ in the hand-gun trial was
because it missed the first application.
The handgun trial is
preliminary, but encouraging data. Of interest is the fact that
the yeast treatment gave equal control of walnut blight as did
the copper treatments. It appeared that Kocide + enhancer and
yeast had fewer infected new buds than did Kocide alone. Work in
this area will continue in 1990.
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Table 1
WALNUT
BLIGHT CONTROL
AIR BLAST SPRAYER TRIAL
-
%
% Blighted % Blighted
Nuts-6
TreatIrentllRate
Ft. Nuts-15
High
Ft. Blighted
High
Nuts
Overall
% Leaf
Phytotoxicity
Clean Bronze
Chanp
5X
Burnt
1-2/3
gallA
2.4 A
3.2 A
2.8 A
77.6
18.6
3.8
8 lbs/A
2.8 A
4.0 A
3.4 A
70.4
24.6
5.0
40.0 B
35.0 B
37.5 B
97.2
00.0
2.8
Kocide
101 - 5X
--
Untreated
1/ Applied 4j2
4/7
4/18
WALNUT
TreatIrent
4/27 and 5/9/89
BLIGHT CONTROL
Rate
..Y
-
HANDGUN
% Leaf Blight
% Blighted Nuts
Charrp - 3X
15.2 mljgal
Kocide - 4X
TRIAL
% Leaf
Phytotoxicity
29.6 AB
29.6 A
20.0 B
9.1 gm/gal
25.6 A
30.4 A
19.0 B
Kocide + Xl-4X
9.1 gm/gal + Xl
22.2 A
31.2 A
20.0 B
Kocide + X2-4X
9.1 gm/gal + X2
17.4 A
28.0 A
23.0 B
Yeast - 4X
1 plate/gal
25.2 A
30.4 A
5.0 A
--
39.6 B
37.6 A
10.0 A
Untreated
!/ Applied
4/4 (except Chanp)~
4/18~ 5/2~ and 5/22/89
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