Light leaf spot fungicides

[Clive]

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.

Yield difference are purely the season 2014 was good for many in my area, 2015 average and 2016 below average

I'm a year behind in my post about ! Time flys ! It should read 2014,15 and 16 16 this last harvest being 1.6 which given the year I was quite happy with !

Pre zero till and with tighter osr rotation my yields were more like 1.25 most years with 1.5 in a good one

 

[Rob E]

not used an autumn fungicide on OSR for many years

I think its more about distributer cashflow than LLS !

NIAB aren't a distributor?

I think like some have said here, rotation frequency and locality seems to be big factor for getting loss of yield from LLS. Would not dare skip autumn fungicide here, but then rotation is a fair way from 1 in 6! I think where risk is high, the disease is underestimated. But often not obvious if risk is high because we don't know enough about the disease.

 

[Feldspar]

Have been doing some more on this topic this morning. I think it's a very interesting one and I think there is a case to be made that fungicides to control LLS are not worthwhile on the whole.

One interesting thing that does seem to come out of the data is that if you're going to spray for LLS, it's better to do it in the autumn rather than in the spring. This seems to go against NIAB at least who in their 2015/2016 Strategies 4 document seem to suggest that the spring stem extension timing is the conventional one.

This paper is a useful one:
http://onlinelibrary.wiley.com/doi/10.1111/j.1744-7348.1994.tb04130.x/abstract

My thinking is that because we have had a very dry summer and early autumn period, and because we're in East Anglia which is considerably lower risk than the rest of the country, that if anyone is going to not benefit from a fungicide it will be us. One factor against that though is that we did have an OSR next to one field last year which was not ploughed but shallow cultivated.

 

[Feldspar]

Also important to note that many of the trials are done in Scotland with OSR following OSR, or in plots with inoculated debris added to introduce the disease.

Also interesting to see not a huge effect in a lot of these trials on phoma control and subsequent yield effect.

 

[Feldspar]

For balance though, although this is quite old, it is more in my part of the world, and they do find significant yield responses:

https://www.cambridge.org/core/jour...il-seed-rape/68DF185B40CAE9E4AA9815A6D0BBEAB5

Again, autumn application seems to be better than a spring one for LLS control. If I were only applying one fungicide, I think I would put it on in the autumn.

 

[Feldspar]

Doing this a bit more scientifically, if you take the best yield response curve, which is y = -0.57 + 0.32L (where y is the % yield change, and L is the % incidence of plants infected with LLS) to increasing incidence of LLS given here:

http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3059.2000.00475.x/full#b14

Then combine it with the likely change in % disease incidence from an autumn fungicide from the Rothamsted forecasting tool here for Elgar sown early in East Anglia (http://www.rothamsted.ac.uk/light-leaf-spot-forecast/crop-specific-interactive-forecast), which gives roughly an 8% reduction in LLS incidence.

This in turn gives a margin benefit of about £30/ha on a 4 t/ha crop, which is more than the £17/ha that the 0.35 l/ha of Proline will cost. I think on balance we're going to put the Proline on now, and then hope we won't have to do a spring one given the later than normal autumn application date.

 

[Lincsman]

The chance of getting £7 extra/acre by spending money 12 months before you will see the cash is a none starter to me. I want a 300% return on chemical expenditure otherwise it does not get done.

 

[JNG]

Grew a field of 4.25t/ha on extrovert last year with no autumn fungicide, the other field got some proline and yielded 3.75, yield not connected to the spray but did not pay for itself and Im sure of that, was out with Kerb last week at 3 degree soil temps, lots of frosts in Ireland lately, one very full field of skye conventional did get some prossaro (.7L/ha) but the opther 80% (all extrovert) rape got no fungicde nor will it, sprayer now put away for the winter.

 

[Rob E]

Some interesting work there, but very old data. I think if we looked at papers on Septoria or yellow rust from 20-30 years ago, we would apply protectant fungicides very differently there too. A lot seems to have changed with these diseases over last 5-10 years. We need more work doing now!

 

[Brisel]

The chance of getting £7 extra/acre by spending money 12 months before you will see the cash is a none starter to me. I want a 300% return on chemical expenditure otherwise it does not get done.

Do you apply that thinking to septoria control in wheat?

 

[Lincsman]

Do you apply that thinking to septoria control in wheat?

Wheat gets 2 fungicides, first around 1st week in May and the last just at ear emergence (micro toxin prevention), what goes on is decided at the time according to disease pressure.

 

[Brisel]

A very low input programme. Well, if that works for you then fine. Here, there would be half the leaves lost to septoria by the first week in May. I digress - I deleted the photos of my light leaf spot infested osr last April despite Jan + March fungicide.

I appreciate that most of the time you'd be fine but the odd crop failure costs more than a prophylactic 0.35 Proline @ £16/ha + application cost. Insurance is costly.

 

[Feldspar]

A very low input programme. Well, if that works for you then fine. Here, there would be half the leaves lost to septoria by the first week in May. I digress - I deleted the photos of my light leaf spot infested osr last April despite Jan + March fungicide.

I appreciate that most of the time you'd be fine but the odd crop failure costs more than a prophylactic 0.35 Proline @ £16/ha + application cost. Insurance is costly.

Application cost is zero when going in with propyzamide anyway.

 

[Lincsman]

A very low input programme. Well, if that works for you then fine. Here, there would be half the leaves lost to septoria by the first week in May. I digress - I deleted the photos of my light leaf spot infested osr last April despite Jan + March fungicide.

I appreciate that most of the time you'd be fine but the odd crop failure costs more than a prophylactic 0.35 Proline @ £16/ha + application cost. Insurance is costly.

As I contract for other Farmers i get to compare what works, or rather pays to do or not do, farming is easy if you just spray everything, skill comes in knowing where to cut costs

I have harvested a OSR crop that I sprayed 8 times, the yield wasnt really different to mine, I think i made most out of that crop!.

 

[Feldspar]

Our OSR had Refinzar at the end of October last year. Come the beginning of March it looked like this:

This either shows that the fungicide didn't do much, or that we would have been in an even situation if we hadn't put one on.

 

[Rob E]

Or disease came in after fungicide ran out of steam?... We don't expect more than a few weeks MAX protection from cereal fungicides, why should we expect 4 months protection in OSR, especially with the way LLS disease develops in the cold?
Looks serious though!
Be nice to have a multisite that existed in OSR like folpet/CTL

 

[Feldspar]

Or disease came in after fungicide ran out of steam?... We don't expect more than a few weeks MAX protection from cereal fungicides, why should we expect 4 months protection in OSR, especially with the way LLS disease develops in the cold?
Looks serious though!
Be nice to have a multisite that existed in OSR like folpet/CTL

The data does suggest though a long-lasting effect from one autumn fungicide - i.e. you can see the difference 4 months on. It might just be that the October fungicide was too early to pick up the initial infection.

 

[franklin]

0.75 teb, or a splash of plover. Price of OSR for next year means its not going to break the bank, while at the same time not giving all the surplus to the chem companies. Mind not made up about the need for autumn PGR, but the cost of the above is very small. Personally would prefer to use a generic so have mixed 0.8lt of a 250g teb in with trace elements etc. Walked crop. No disease. Bit leafy. High LLS resistance. Will save the money for spring. You can easily get carried away with the "worth a pile / insurance" talk, especially if you havent actually sold any forward! Try to line your own pockets before Syngentas.

Be nice to have a multisite that existed in OSR like folpet/CTL

Be nice if we could use Cycocel for PGR. Be nice if we could use Aviator rather than Skyway.

Not sure what % of leaf area in mid November adds to crop yield come harvest. I was of the impression that German crops could be pretty much defoliated over winter and still perform well. In that case, do we just need to keep the rosette / buds / heart of the plant clean from infection? I understand that milder winters here mean any nasties on scensced leaves could infect the main plant. Lets hope the start of some good frosts help.

 

[Feldspar]

0.75 teb, or a splash of plover. Price of OSR for next year means its not going to break the bank, while at the same time not giving all the surplus to the chem companies. Mind not made up about the need for autumn PGR, but the cost of the above is very small. Personally would prefer to use a generic so have mixed 0.8lt of a 250g teb in with trace elements etc. Walked crop. No disease. Bit leafy. High LLS resistance. Will save the money for spring. You can easily get carried away with the "worth a pile / insurance" talk, especially if you havent actually sold any forward! Try to line your own pockets before Syngentas.



Be nice if we could use Cycocel for PGR. Be nice if we could use Aviator rather than Skyway.

Not sure what % of leaf area in mid November adds to crop yield come harvest. I was of the impression that German crops could be pretty much defoliated over winter and still perform well. In that case, do we just need to keep the rosette / buds / heart of the plant clean from infection? I understand that milder winters here mean any nasties on scensced leaves could infect the main plant. Lets hope the start of some good frosts help.

Not convinced about this defoliation theory. NIAB did some simulated pigeon grazing trials by mowing the crop at different heights (to miss growing point or not). The less mowing the better was the result IIRC.

 

[franklin]

Wasnt saying to go chop them off. Just wondering what these old leaves actually bring to the crop yield come spring? I have a real bee in my bonnet about spraying boron onto leaves that have essentially done their job and are now dying naturally. The old Morley trials on plants with fairly bobbins LLS scores showed very poor response from autumn fungicides.

Could be that I am just a sceptic, and that when I see my agronomist running around my farm flapping his arms like an angered chicken screeching "rainsplash event" my brain interprets that as some kind of modified mating call - ie he is in love with my chequebook yet it is me who is going to get the bumming.

Your pic above though would get me reaching for the chem. Could find nothing in the crops here this year.