Abstract
We studied several factors influencing the efficacy of the demethylation inhibitor (DMI) fungicide myclobutanil and the strobilurin fungicide azoxystrobin for control of grape black rot, caused by the pathogen Guignardia bidwellii (anamorph Phyllosticta ampelicida). The distribution of sensitivities to myclobutanil among G. bidwellii isolates from an “organic” vineyard (no previous exposure to synthetic fungicides, n = 50) and from a commercial vineyard with a history of DMI applications (n = 60) was determined in vitro. There was little difference between the two populations, and the range of sensitivities was narrow; for the composite population of 110 isolates, the value of the mean effective dose for 50% inhibition (ED 50 ) was 0.04 mg/liter, and the most- and least-sensitive isolates were separated by a factor of 16. When applied from 2 to 6 days after inoculating grape seedlings with a suspension containing either 2 × 10 4 or 1 × 10 6 conidia per ml, myclobutanil (60 mg/liter) provided complete control of lesion development. When applied beyond 6 days after inoculation but prior to lesion appearance (9 to 11 days after inoculation, depending on temperature), it provided complete control of pycnidium production in those lesions that developed subsequently. In contrast, when applied 2 to 10 days after inoculation with 2 × 10 4 conidia per ml, azoxystrobin (128 mg/liter) provided only 78 to 63% control of lesion formation and erratic control of pycnidium formation, although conidium production was reduced by 85 to 68% across this range of treatments. Relatively little control was provided by azoxystrobin treatments following inoculation with 1 × 10 6 conidia per ml. On leaf disks treated with azoxystrobin at 20 mg/liter prior to inoculation, 8 to 43% of conidia from five G. bidwellii isolates germinated, and 4 to 19% formed appressoria. However, these processes were completely to near-completely inhibited when salicylhydroxamic acid (SHAM), which inhibits an alternative respiration pathway utilized to circumvent the activity of strobilurin fungicides, was added to the inoculum at 100 mg/liter. Thus, alternative respiration apparently allowed the conidia to germinate and form appressoria on azoxystrobin-treated leaves. When grape seedlings were sprayed with commercially formulated azoxystrobin at 200 mg/liter and inoculated the next day with G. bidwellii conidia, little or no disease was evident 4 weeks later. However, G. bidwellii pycnidia formed on up to 50% of the leaves from such plants when they were killed with paraquat 1 to 7 days after inoculation. These results suggest that latent infections became established on azoxystrobin-treated leaves and became active after the plants were killed with paraquat.
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Claims 15
Claim · model-written summary
G. bidwellii populations from organic and commercial vineyards had little difference in myclobutanil sensitivity.
Verbatim
e0“There was little difference between the two populations, and the range of sensitivities was narrow; for the composite population of 110 isolates, the value of the mean effective dose for 50% inhibition (ED 50 ) was 0.04 mg/liter, and the most- and least-sensitive isolates were separated by a factor of 16.”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
The most and least myclobutanil-sensitive pathogen isolates differed by a factor of 16.
Verbatim
e0“the most- and least-sensitive isolates were separated by a factor of 16”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Myclobutanil applied 2–6 days after inoculation completely controlled grape lesion development.
- Taxon
- grapee0
- Treatment
- myclobutanil (60 mg/liter)e0
- Interactor
- conidiae0pathogen
- Outcome
- lesion developmente0
- Direction
- complete controle0
Not reportedComparator
Verbatim
e0“When applied from 2 to 6 days after inoculating grape seedlings with a suspension containing either 2 × 10 4 or 1 × 10 6 conidia per ml, myclobutanil (60 mg/liter) provided complete control of lesion development.”
Claim · model-written summary
Later pre-symptom myclobutanil application completely controlled pycnidium production in subsequent lesions.
- Taxon
- grapet0
- Outcome
- pycnidium productione0
- Direction
- complete controle0
- Qualifier
- beyond 6 days after inoculatione0
Not reportedTreatmentComparator
Verbatim
e0“When applied beyond 6 days after inoculation but prior to lesion appearance (9 to 11 days after inoculation, depending on temperature), it provided complete control of pycnidium production in those lesions that developed subsequently.”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Azoxystrobin controlled grape lesion formation by 78 to 63% after low-dose inoculation.
- Taxon
- grapet0
- Treatment
- azoxystrobin (128 mg/liter)e0
- Outcome
- lesion formatione0
- Direction
- controle0
- Value
- 78 to 63%e0
Not reportedComparator
Verbatim
e0“azoxystrobin (128 mg/liter) provided only 78 to 63% control of lesion formation and erratic control of pycnidium formation, although conidium production was reduced by 85 to 68% across this range of treatments.”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Azoxystrobin had erratic control of pathogen pycnidium formation.
- Taxon
- grapet0
- Treatment
- azoxystrobin (128 mg/liter)e0
- Outcome
- pycnidium formatione0
- Direction
- erratic controle0
Not reportedComparator
Verbatim
e0“azoxystrobin (128 mg/liter) provided only 78 to 63% control of lesion formation and erratic control of pycnidium formation”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Azoxystrobin reduced pathogen conidium production by 85 to 68%.
Not reportedTreatmentComparator
Verbatim
e0“conidium production was reduced by 85 to 68% across this range of treatments”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Azoxystrobin gave little disease control after inoculation at the higher conidial concentration.
- Taxon
- grapet0
- Treatment
- azoxystrobin treatmentse0
- Outcome
- controle0
- Direction
- Relatively littlee0
- Qualifier
- 1 × 10 6 conidia per mle0
Not reportedComparator
Verbatim
e0“Relatively little control was provided by azoxystrobin treatments following inoculation with 1 × 10 6 conidia per ml.”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
On azoxystrobin-treated grape leaf disks, 8 to 43% of pathogen conidia germinated.
- Taxon
- grapet0
- Interactor
- G. bidwellii
Phyllosticta ampelicidae0pathogen - Outcome
- conidia from five G. bidwellii isolates germinatede0
- Value
- 8 to 43%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“On leaf disks treated with azoxystrobin at 20 mg/liter prior to inoculation, 8 to 43% of conidia from five G. bidwellii isolates germinated”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
On azoxystrobin-treated grape leaf disks, 4 to 19% of pathogen conidia formed appressoria.
Verbatim
e0“4 to 19% formed appressoria”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Adding SHAM nearly or completely inhibited pathogen germination and appressorium formation.
- Taxon
- grapet0
- Treatment
- salicylhydroxamic acid (SHAM)e0
- Outcome
- these processese0
- Direction
- completely to near-completely inhibitede0
- Value
- 100 mg/litere0
Not reportedComparator
Verbatim
e0“these processes were completely to near-completely inhibited when salicylhydroxamic acid (SHAM), which inhibits an alternative respiration pathway utilized to circumvent the activity of strobilurin fungicides, was added to the inoculum at 100 mg/liter”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Alternative respiration apparently enabled pathogen conidia to germinate and form appressoria on treated leaves.
Verbatim
e0“alternative respiration apparently allowed the conidia to germinate and form appressoria on azoxystrobin-treated leaves”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Azoxystrobin-sprayed grape seedlings showed little or no disease four weeks after inoculation.
- Taxon
- grapee0
- Treatment
- commercially formulated azoxystrobin at 200 mg/litere0
- Interactor
- G. bidwelliiPhyllosticta ampelicidae0pathogen
- Outcome
- diseasee0
- Direction
- little or noe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When grape seedlings were sprayed with commercially formulated azoxystrobin at 200 mg/liter and inoculated the next day with G. bidwellii conidia, little or no disease was evident 4 weeks later.”
Claim · model-written summary
Pathogen pycnidia formed on up to half of azoxystrobin-treated grape leaves killed after inoculation.
- Taxon
- grapet0
- Interactor
- G. bidwelliiPhyllosticta ampelicidae0pathogen
- Outcome
- G. bidwellii pycnidia formede0
- Value
- up to 50%e0
- Qualifier
- killed with paraquat 1 to 7 days after inoculatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“G. bidwellii pycnidia formed on up to 50% of the leaves from such plants when they were killed with paraquat 1 to 7 days after inoculation.”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
Claim · model-written summary
Latent pathogen infections apparently established on treated grape leaves and activated after paraquat killing.
Verbatim
e0“latent infections became established on azoxystrobin-treated leaves and became active after the plants were killed with paraquat”
t0“Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot”
The same questions in other papers
azoxystrobin · disease · VitisPositive and negative results
8 papers in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
- positive
6 papers more in this group
See all 10 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.