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| Summaries
and recommendations for 2001 |
The FRAC-SBI (formerly DMI) working
group was set up in 1982. The group meets annually to review monitoring
data and to agree recommendations for the use of SBI fungicides.
The 2000 meeting reviewed the most recent monitoring work undertaken
directly by Agrochemical Companies or sponsored by them with academic
institutions. Based on a review of these data, statements have been
prepared which summarise the most up-to-date knowledge available
regarding resistance to SBI fungicides.
Dr Bruns, Dr Hall, Mr evans, Mr Gaujard and Mr Filippini were welcomed
to the group.
The 2000 meeting of the FRAC-SBI Working group took place at 19th
October at the Sheraton Frankfurt Conference Centre.
Working Group members present at the 2000 meeting
| Dr. K.H.
Kuck (Chairman) |
Bayer AG Crop Protection Business
Group, Monheim, Germany |
| Dr. C. Longhurst (Secretary) |
DowAgroSciences, European Research and Development,
Letcombe, UK |
| Mr. P. Evans |
Aventis CropScience, Lyon, France |
| Dr. R. Birchmore |
Aventis CropScience, Lyon, France |
| Dr J Speakman |
BASF, Crop Protection Division, Limburgerhof,
Germany |
| Mr C Gaujard |
Aventis CropScience, Lyon, France |
| Dr R Siebert |
Bayer AG, Crop Protection Business Group, Monheim,
Germany |
| Dr J Bruns |
DuPont de Nemours (France) SA, Centre Europeen
de R&D |
| Mr. L. Filippini |
Isagro Ricerca, Milan, Italy |
| Dr O Puppin |
Isagro Ricerca, Milan, Italy |
| Dr KM Chin |
Novartis Crop Protection, AG, Witterswil, Switzerland |
| Dr A Hall |
Zeneca Agrochemicals, UK |
The meeting reviewed the most recent monitoring
work undertaken directly by Agrochemical Companies or sponsored by
them with external institutions. Based on a review of these data,
statements have been prepared which summarise the most up-to-date
knowledge available regarding resistance to SBI fungicides.
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| Key
Points from meeting |
Generally in 2000 a stable
situation was found with DMI’s and morpholines.
Wheat
 Powdery
mildew: stable situation (DMI and morpholines)
Septoria
tritici: stable situation (DMI)
Yellow
and brown rust: field performance of DMI’s
remains good.
Eyespot:
Generally stable, increasing sensitivity in France
to prochloraz.
Barley
Rhynchosporium:
stable situation DMI sensitivity unchanged.
Net
blotch: Performance unchanged.
Powdery
mildew: SBI performance and sensitivity.
Vines
Powdery
mildew: stable situation.
Apples
Scab:
DMI performance unchanged.
Powdery
mildew: DMI performance unchanged.
Bananas
Black
sigatoka: 1999 SBI sensitivity stable. Performance
unchanged.
Quinoxyfen
(non-SBI powdery mildewicide)
Wheat
and Grape powdery mildew : stable situation
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| DEFINITIONS |
| SBI-Fungicides
There are two major classes of fungicides that comprise
the Sterol Biosynthesis Inhibitor's (abbreviated SBI's):
the DMI-fungicides and the so-called "Morpholine"-fungicides.
Both classes inhibit targets within fungal sterol biosynthesis
but differ in regard to the precise target sites they
inhibit.
The SBI based fungicides represent an important class
of agricultural fungicides. They make a major contribution
to world agricultural production via their broad spectrum
of disease control and excellent field performance.
DMI-Fungicides
SBI-fungicides that inhibit the C14 demethylation
step within fungal sterol biosynthesis are now commonly
characterised as DeMethylation-Inhibitors (Abbreviation:
DMI’s).
Chemically, DMI’s belong to different classes.
Beside triazoles, numerous imidazoles, pyridines and
pyrimidine all have been shown to act as demethylation
inhibitors.
Typically, DMI's have a broad spectrum of activity
against a range of economically important pathogens
on arable crops, top fruit, vines, plantation crops,
etc.
"Morpholine"-Fungicides
Like the DMI’s the "Morpholine"-fungicides
also belong to different chemical classes. The first
representatives of this group were chemically morpholines.
Although representatives of two other chemical groups
(piperidines and spiroketalamines) have entered the
market, the group designation "Morpholines" is
now commonly used for all three chemical classes.
"Morpholines" inhibit (to a variable degree)
two target sites within the sterol biosynthetic pathway,
the D
8 ® D 7
isomerase and the D 14 reductase.
"Morpholines" have a narrower spectrum of
activity than the DMI’s. They can be used alone
but are often used in mixtures with DMI's to control
cereal powdery mildews and rusts.
Resistance to fungicides
Resistance to fungicides is a normal phenomenon embodied
in the natural process of the evolution of biological
systems. By close co-operation within the agrochemical
industry and collaboration with researchers, advisors
and with growers we can ensure that the SBI fungicides
are used optimally and continue to offer the benefits
they currently confer.
Cross Resistance among SBI-fungicides
Whilst there is positive cross-resistance amongst
the DMI's and amongst the "morpholines",
there is no cross-resistance between the DMI's and
the "morpholines".
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| 1.
CEREAL DISEASES |
1.1 BARLEY DISEASES |
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1.1.1 |
Barley powdery mildew (Erysiphe graminis f.sp.
hordei / Blumeria graminis f.sp. hordei)
In 2000 disease pressure was generally low to
moderate.
DMI’s
DMI’s performed as expected.
"Morpholines"
Morpholine products performed well when applied
according to label recommendations and performance
was excellent in all regions, Sensitivity was
stable. |
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1.1.2 |
Net Blotch (Pyrenophora teres/Drechslera teres)
Disease incidence was moderate in 2000..
Field disease control was generally good with
no problems reported. |
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1.1.3 |
Scald (Rhynchosporium secalis)
Disease pressure was very high in 2000, especially
in the UK and France. The performance of DMI’s
was acceptable, when used according to manufacturers’ recommendations.
Sensitivity was stable
It is recommended that mixtures with effective
non-DMI fungicides be used for disease control
and that curative treatments should be avoided. |
1.2 WHEAT DISEASES |
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1.2.1 |
Wheat powdery mildew (Erysiphe graminis f.sp.
tritici / Blumeria graminis f.sp. tritici)
Disease pressure was low for most of the season,
dry conditions reduced disease pressure in many
parts of Europe after initial outbreaks.
"Morpholines"
The sensitivity situation has remained stable
in all monitored countries over several years.
Field performance of morpholine based products
was good when applications followed manufacturers’ recommendations.
DMI's
Sensitivity data was presented for tebuconazole.
The situation was generally stable.
Performance of DMI based products was as expected.
Quinoxyfen
Methods for establishing sensitivity have being
established for the phenoxyquinoline, quinoxyfen.
There have been no shifts to less sensitive strains
in 1997 - 2000 over the baseline established in
1996.
Performance was as expectd.
This compound is not an SBI but is being reviewed
under the SBI-FRAC umbrella for convenience. |
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1.2.2 |
Wheat Brown Rust (Puccinia recondita)
As in previous years, DMI fungicides continued
to provide excellent disease control. |
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1.2.3 |
Wheat Yellow Rust (Puccinia striiformis)
As in previous years, DMI fungicides continued
to provide good disease control
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1.2.4 |
Wheat Leaf Spot (Mycosphaerella graminicola / Septoria
tritici)
Disease pressure was medium in the U.K. , Germany
and France in 2000.
Sensitivity was stable in 2000.
Effective DMI’s continued to provide good
disease control. |
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1.2.5 |
Wheat Glume Blotch (Stagonospora nodorum = Septoria
nodorum)
Good control with DMI's was obtained.
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1.2.6 |
Wheat Eyespot (Pseudocercosporella herpotrichoides)
Disease pressure was medium (U.K., Germany) to
high (France). Efficacy levels of Prochloraz maintained.
There were no reports of unacceptable performance.
The frequency of isolates more sensitive to prochloraz
continues to increase. |
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| RECOMMENDATIONS
FOR CEREALS |
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The recommendations for the use of DMI and "morpholine" fungicides
in mixture or alternation programmes with different
mode of action fungicides remain unchanged. |
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Repeated application of DMI or "morpholine" fungicides
alone should not be used on the same crop in one
season against a high risk pathogen (e.g. cereal
powdery mildews, barley net blotch or barley scald)
in areas of high disease pressure for that particular
pathogen. |
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Split / reduced rate programmes using repeated
applications which provide continuous selection pressure
should be avoided. |
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To ensure good performance in situations of high
disease pressure it is of importance to adhere to
dosages and spray timings as recommended on the label. |
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The "morpholine" fungicides
are effective cross-resistant partner fungicides
for DMI’s on cereals for the control of powdery
mildew. |
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Effective fungicides from non-DMI classes should
be used as partner fungicides for DMI's on cereals
for the control of barley leaf spot diseases. |
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| 2.
NON-CEREAL DISEASES |
2.1
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Grape Powdery Mildew (Uncinula necator)
Disease pressure was moderate across Europe. No
complaints were received and overall performance
of DMIs was generally good when products were used
according to the manufacturer's recommendations
for rate and timing.
Spiroxamine was presented for the first time:
There has been no change in sensitivity from the
baseline over three years.
Quinoxyfen : The baseline data was presented.
Recommendations :
DMIs should only be used as preventative and not
in a curative manner.
The existing strategy for effective disease control
and resisitance management comtinues to be succesful
and the use recommendation is a maximum
of 4 application
per season, before symptoms occur. Possible strategies
include the use of mixtures or alternation with
non-cross resistant fungicides.
To ensure the DMIs can remain as the effective
basis for Uncinula control in vines, the use of
the full recommended rate (either alone or in mixture),
recommended timing, application volume and accurate
treatment of each row should be adhered to. |
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2.2
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Apple Scab (Venturia inaequalis)
No complaints were received on the performance
of DMI’s on this disease in 2000 when compounds
were used according to the manufacturers’ recommendation
and FRAC recommendations.
Recommendations
DMI fungicides, which are labelled for scab control,
are not recommended for season long use and a maximum
of 4 DMI sprays either alone or in mixture is recommended.
Where repeated fungicide applications are required,
DMI's should be used in mixtures or (block) alternations
with a non-cross resistant fungicide.
(Block) alternations should be limited to a total
of 4 sprays/season.
Preventative applications should always be the
first choice with DMI’s. Curative applications
are only recommended when accurate disease warning
systems are available. Application of recommended
label rates. |
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2.3
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Apple Powdery Mildew (Podosphaera leucotricha)
No complaints were received on the performance
of DMI’s when compounds were used acording
to manufacturers' recommendation and FRAC recemmendations.
For recommendations see General Recommendations. |
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2.4 |
Banana Sigatoka (Mycosphaerella fijiensis)
No shifts in sensitivity were seen in data presented
at the Banana-FRAC meeting in February 2000. No
problems were encountered with controlling disease
with DMIs in practice.
The recommendations as outlined in the summaries
of the Banana FRAC-SBI Working Group meeting of
February 2000, remain generally unchanged regarding
DMI’s and "morpholines". The use
of these FRAC guidelines should be encouraged in
all bana growing areas.
All fungicides belonging to the DMI’s have
to be considered as one product group amongst which
general cross-resistance exists. Accordingly, alternation
or mixtures of DMI’s are of no value for
resistance management and must not be recommended
for the purpose of resistance management. |
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2.5
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Sugar Beet Leaf Spot (Cercospora beticola)
Disease control in 2000 remained good; the general
recommendations for resistance management of SBI’s
should be followed. |
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| GENERAL
RECOMMENDATIONS FOR THE USE OF SBI FUNGICIDES |
The SBI fungicides represent one of
the most potent classes of fungicides available to
the grower for the control of many economically important
pathogens. It is in the best interest of all those
involved in recommending and using these fungicides
that they are utilised in such a way that their effectiveness
is maintained.
The summaries and recommendations included in this
report are based upon data generated by members of
the FRAC-SBI Working Group and upon the work of non-industry
collaborators. The working group concentrates its resources
on the major crop/pathogen targets from the point of
view of resistance risk. Inevitably many, still important,
pathogens are omitted. To help in making recommendations
for crops and pathogens not directly covered above,
the following general recommendations can be made:
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Repeated application of SBI fungicides alone
should not be used on the same crop in one season
against a high risk pathogen in areas of high disease
pressure for that particular pathogen. |
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For crop/pathogen situations where repeated spray
applications (e.g. orchard crops/powdery mildew)
are made during the season, alternation (block
sprays or in sequence) or mixtures with an effective
non cross-resistant fungicide are recommended. |
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Where alternation or the use of mixtures is not
feasible because of lack of effective or compatible
non cross-resistant partner fungicides, then input
of SBI's should be reserved for critical parts
of the season or crop growth stage. |
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Where DMI's or "morpholine" performance
is declining generally and sensitivity testing
has confirmed the presence of less sensitive forms,
SBI's should only be used in mixture or alternation
with effective non cross-resistant partner fungicides. |
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The introduction of the new classes
of chemistry offers new opportunities for more
effective resistance management. |
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Users must adhere to the manufacturers’ recommendations.
In many cases, reports of "resistance" have,
on investigation, been attributed to cutting recommended
rates of use, or to poor or miss-timed application. |
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Fungicide input is only one aspect of crop management.
Fungicide use does not replace the need for resistant
crop varieties, good agronomic practice, plant
hygiene/sanitation, etc. |
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