Light leaf spot fungicides

Feldspar · Nov 25, 2016

We have got Kerb to put on early next week. Haven't sprayed for phoma because we haven't seen any. It has been suggested to put Proline on at 0.35 l/ha for LLS.

I need to learn more about this application. Is prothio really much better than tebuconazole? What is the yield response from a fungicide at this timing? Does careful field inspection make a big difference, or is it going on before any obvious signs of disease are present?

With OSR prices atm moment I'm not about to start wildly experimenting, and so a decision to go against the norm will need to be well evidenced. Any thoughts (backed up by evidence)?

Gong Farmer · Nov 25, 2016

In the field you are very unlikely to see LLS before the New Year but if you wait till then to treat it will be too late. All fungicides are protectant against this disease so autumn treatment is a must.

If you want to get to stem extension before you have to spray again, then yes, prothio is better than teb.

Feldspar · Nov 25, 2016

Fromebridge said:
In the field you are very unlikely to see LLS before the New Year but if you wait till then to treat it will be too late. All fungicides are protectant against this disease so autumn treatment is a must.

If you want to get to stem extension before you have to spray again, then yes, prothio is better than teb.

Thanks. Have found roughly this advice in the current Strategy 1 document.

I see in the 2016 Variety Interactions Handbook (section 4.8) that some work is being down on low, medium and high input fungicide regimes in OSR for the latest varieties which should be useful in answering this question.

yellow belly · Nov 25, 2016

If a variety has high resistance to lls is there need for an autumn fungicide
Most trials are with older varieties with low resistance
I will treat in the early spring protecting new growth then

Feldspar · Nov 25, 2016

yellow belly said:
If a variety has high resistance to lls is there need for an autumn fungicide
Most trials are with older varieties with low resistance
I will treat in the early spring protecting new growth then

Growing Elgar which has a resistance score of 7.

I seem to remember @Clive and @richard hammond don't normally put a LLS spray on, opting for a single spray at stem extension IIRC.

We put Refinzar on last year for phoma, but then got quite a bit of LLS before the stem extension fungicide. I was laid up in bed for all of that time and so we let it get reasonably bad. Still had the crop yielding up to decent levels where the pigeons didn't get it. Not scientific enough for me though.

Clive · Nov 25, 2016

Feldspar said:
Growing Elgar which has a resistance score of 7.

I seem to remember @Clive and @richard hammond don't normally put a LLS spray on, opting for a single spray at stem extension IIRC.

We put Refinzar on last year for phoma, but then got quite a bit of LLS before the stem extension fungicide. I was laid up in bed for all of that time and so we let it get reasonably bad. Still had the crop yielding up to decent levels where the pigeons didn't get it. Not scientific enough for me though.

not used an autumn fungicide on OSR for many years

I think its more about distributer cashflow than LLS !

Clive · Nov 25, 2016

Feldspar said:
We have got Kerb to put on early next week. Haven't sprayed for phoma because we haven't seen any. It has been suggested to put Proline on at 0.35 l/ha for LLS.

I need to learn more about this application. Is prothio really much better than tebuconazole? What is the yield response from a fungicide at this timing? Does careful field inspection make a big difference, or is it going on before any obvious signs of disease are present?

With OSR prices atm moment I'm not about to start wildly experimenting, and so a decision to go against the norm will need to be well evidenced. Any thoughts (backed up by evidence)?

have you had much frost yet ? still feel its a bit early for kerb here yet

Feldspar · Nov 25, 2016

Clive said:
have you had much frost yet ? still feel its a bit early for kerb here yet

Yes, have had some. Some more severe ones forecast next week.

Feldspar · Nov 25, 2016

Clive said:
not used an autumn fungicide on OSR for many years

I think its more about distributer cashflow than LLS !

Based on your farm observations, or is there any independent trial data to back it up? Your recent OSR yields have been good IIRC so your strategy is hardly disastrous. What about the claim that it's difficult to control once established?

Clive · Nov 25, 2016

Feldspar said:
Based on your farm observations, or is there any independent trial data to back it up? Your recent OSR yields have been good IIRC so your strategy is hardly disastrous. What about the claim that it's difficult to control once established?

based on not doing it for the last 10 years or so and still getting decent yields comparable with what I'm told others are getting

No control so not at all justifiable or provable just like my much reduced insecticide use, just what appears to work for us and produce decent crops at an affordable price that leaves a margin

Clive · Nov 25, 2016

Feldspar said:
Yes, have had some. Some more severe ones forecast next week.

just looking at the forecast - might do ours end of next week if those frosts come

Feldspar · Nov 25, 2016

Just looking around for some relevant research, I came across this (from page 153 onwards):

http://www.sipr.ac.uk/CPNB/Index_and_Proceedings_2014.pdf#page=162

They had no significant yield responses from prothioconazole applications. There often seems to be an explanation when no significant yield responses occur which always belies the impression that the underlying hope was that a significant response was going to occur. In a way, I'd rather there was no benefit from putting fungicides on, because they I wouldn't have to worry about them.

Looking through the data in that link there are two things to note. Firstly, the fungicide didn't do a very good job of controlling the LLS, and, secondly, even when some varieties had significantly higher levels of LLS in the spring in the untreated plots, they didn't have a significantly different yields, which suggests the plants will tolerate some LLS without their yield being significantly affected.

Feldspar · Nov 25, 2016

Clive said:
based on not doing it for the last 10 years or so and still getting decent yields comparable with what I'm told others are getting

No control so not at all justifiable or provable just like my much reduced insecticide use, just what appears to work for us and produce decent crops at an affordable price that leaves a margin

IIRC you do one tebuconazole in OSR normally. Is that for LLS or from sclerotinia?

Lincsman · Nov 25, 2016

Never put a fungicide on OSR yet... at any time, ..or a desiccant.. . most of the seed is off the heap..still get 1.5t/ac ..... I make a fortune out of it!

Rob Holmes · Nov 25, 2016

Planning to go with Refinzar + Trace elements +Kerb next week

Feldspar · Nov 25, 2016

Lincsman said:
Never put a fungicide on OSR yet... at any time, ..or a desiccant.. . most of the seed is off the heap..still get 1.5t/ac ..... I make a fortune out of it!

How often do you grow it in your rotation?

Brisel · Nov 25, 2016

Prothio or Refinzar for LLS. The penthiopyrad in Refinzar is supposed to be good for rooting but I think it's too late in the year for much extra growth above or below ground.

0.35 Proline going on next week with the Solitaire or Astrokerb as appropriate.

Clive · Nov 25, 2016

Feldspar said:
IIRC you do one tebuconazole in OSR normally. Is that for LLS or from sclerotinia?

No fixed plan, go on the season but etc but a single cheap spring teb has been what we have done the last 3 years

Yields have been good - certainly as much as I would realistically expect on our soils from memory ave t/ac (over planted acres) 1.98t 2013 1.85 2014 and 1,6 2015

Lincsman · Nov 25, 2016

Feldspar said:
How often do you grow it in your rotation?

Every 6 years, OSR, w/w w/w vining peas, w/w w/w

Ugo79 · Nov 25, 2016

Clive said:
No fixed plan, go on the season but etc but a single cheap spring teb has been what we have done the last 3 years

Yields have been good - certainly as much as I would realistically expect on our soils from memory ave t/ac (over planted acres) 1.98t 2013 1.85 2014 and 1,6 2015

Your yields appear to be on the slide... 1.35 2016?

Playing devils advocate...Perhaps your approach to light leaf spot control is allowing a gradual build up of inoculum on the farm which is leading to a gradual yield decline with each passing crop as they experience higher levels of Light leaf spot infection.

Your spring dose of Teb used to 'hold' off the low levels of disease experienced 5 years ago but with the annual increase in autumn infection this approach is no longer working.

....However I appreciate the decline might not be solely related to disease.

Light leaf spot fungicides

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