| EFFECT OF FUNGICIDE ON MYCOTOXIN PRODUCTION |
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Mycotoxins are secondary metabolites produced by
some of the FHB pathogens in the UK. It is thought that in some cases the role
of the toxin may be to aid infection of the plant by the pathogen. Mycotoxins
are of concern due to their potentially harmful effect to both humans and animals.
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Mycotoxins produced by FHB pathogens
in the UK include:
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| Fusarium species |
Main mycotoxins produced |
| F. culmorum |
Deoxynivalenol, nivalenol, zearalenone |
| F. graminearum |
Deoxynivalenol, nivalenol, zearalenone |
| F. avenaceum |
Enniatins |
| F. poae |
HT-2 and T-2 toxins, diacetoxyscirpenol, nivalenol |
| M. nivale |
None confirmed |
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The European Commission is currently
evaluating the risk posed by a number of trichothecenes toxins produced by Fusarium
species. These include deoxynivalenol (DON), nivalenol (NIV), T-2 toxin, HT-2
toxin and zearalenone. Maximum limits in foodstuffs will be introduced shortly.
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Currently, there is no one fungicide
on the market capable of giving 100% control of FHB.
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To date the best control achieved
is between 60 and 70%. However to achieve this level of control the fungicide
needs to be applied at the correct time.
- Optimal fungicide timing = five days pre or post inoculum arriving on the ear
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This can be difficult to achieve and as a result fungicides should be used only as part of an integrated
management program.
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As part of a three-year project funded
by the HGCA (Project Report No. 297), several trials have been carried out at
CSL to investigate the effectiveness of fungicides against FHB. Unless otherwise
stated the results presented are from CSL trials.
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The trials were carried out on plots
artificially inoculated with a mixed conidial suspension containing F. culmorum,
F. graminearum, F. avenaceum, F. poae and M. nivale
vars nivale and majus. Plot humidity was maintained at a level
greater than 70% for five days following inoculation.
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Grain was analysed for deoxynivalenol (DON) content using either DON FAST kits
(r-biopharm) or GC/MS. Results from trials carried out between 1999 and 2001
are presented.
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| 1999 |
The effect of a range of fungicides, applied at full rate, on mycotoxin production were investigated.
All fungicides were applied two days post inoculation.
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Fungicides applied were difenoconazole (as �Plover� at 0.3 l/ha), kresoxim-methyl + epoxiconazole
(as �Landmark� at 1 l/ha), metconazole (as �Caramba� at 1.5 l/ha), carbendazim (as �Derosal WDG� at 400 g/ha),
azoxystrobin (as �Amistar� at 1 l/ha), tebuconazole (as �Folicur� at 1 l/ha) and prochloraz (as �Sportak� at 0.9 l/ha).
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- No reduction in DON level was seen following treatment with azoxystrobin or difenoconazole.
- All other fungicide treatments significantly reduced the level of DON. The greatest reductions were seen following
treatment with carbendazim, tebuconazole or metconazole.
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| 2000 |
The effects of fungicide rate and fungicide mixtures on mycotoxin production were investigated.
All fungicides were applied two days post inoculation.
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Fungicides applied were tebuconazole (as �Folicur� at 1 l/ha and 0.5 l/ha), metconazole (as �Caramba� at
1.5 l/ha and 0.75 l/ha), azoxystrobin (as �Amistar� at 1 l/ha and 0.5 l/ha), kresoxim-methyl + epoxiconazole
(as �Landmark� at1 l/ha), epoxiconazole (as �Opus� at 1 l/ha and 0.5 l/ha), tebuconazole + azoxystrobin
(as �Folicur� and �Amistar� both at 0.5 l/ha), metconazole + azoxystrobin (as �Caramba� and �Amistar� at 0.75 l/ha
and 0.5 l/ha respectively), and epoxiconazole + azoxystrobin (as �Opus� and �Amistar� both at 0.5 l/ha).
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| CSL, York |
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- Significant differences in the level of DON were seen between the treatments.
- The level of DON present in the grain was reduced by all treatments with the exception of azoxystrobin
(full and � rate).
- Levels of DON were lower following the application of a full rate straight formulation when compared to the equivalent application at � rate.
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| Morley Research Centre, Wymondham, Norfolk |
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- No fungicide application gave a significant reduction in the level of DON present in the grain.
- Tebuconazole and metconazole were the most effective treatments.
- Treatment with a straight formulation of azoxystrobin (at either full rate or half rate) significantly
increased the level of DON found in grain.
- DON levels were lowered, compared to the straight azoxystrobin application, if azoxystrobin was applied
in mixture with a triazole.
- The application of kresoxim methyl + epoxiconazole did not increase the levels of DON.
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| 2001 |
The effect of fungicide rate and application timing on mycotoxin production was investigated. Fungicides
were applied to plots either 2 days pre -inoculation (S1) or 2 days post inoculation (S2).
Inoculum levels were reduced Levels of inoculum used to artificially infect the plots were reduced compared
to previous years in order to achieve disease levels comparable to a natural infection.
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Fungicides applied were tebuconazole (as 'Folicur' at 0.5 l/ha and 0.25 l/ha), azoxystrobin (as 'Amistar'
at 0.5 l/ha and 0.25 l/ha) and tebuconazole + azoxystrobin (as 'Folicur' and 'Amistar' both at 0.5 l/ha and 0.25 l/ha).
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- Mycotoxin levels on control plots were much lower than in previous years
(2.6 ppm compared to circa 12 ppm).
- All fungicide treatments, with the exception of the pre-inoculation azoxystrobin/tebuconazole (0.25 l/ha) treatment,
significantly reduced the level of mycotoxin compared to the control plots. No other significant differences were
seen.
- In general the higher the fungicide application rate the lower the level of toxin in grain. No difference in
DON levels was seen between the two fungicide application times.
- Reducing the level of inoculum applied to the ear reduced the differences in fungicide efficacy seen in previous
years.
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