Is BYDV linked to herbicide use?

[Dan Powell]

My usual strategy here for autumn cereals is no pre-em apart from glyphosate and then pendimethalin (eg Crystal) + DFF at 1 leaf with some manganese and an insecticide if necessary. No black grass here...

Now here is a theory based on observation.

No BYDV in November sown wheat where ploughed. Also no herbicide used on said crop until spring.

Worse BYDV in one area of barley where double dosed with spray due to tractor PTO stopping and me not knowing exactly where it had happened.

Anecdotal evidence of no BYDV from other no till farms (@SilliamWhale , @Clive) where the strategy was pre-em and shut the gate.

So the question is: do leaf applied herbicides stress the crop and therefore make it more susceptible to disease e.g. BYDV and therefore would I be better off doing a pre-em in future?

 

[Gadget]

Here are some similar thoughts
http://www.bristol.ac.uk/news/2016/april/polarization-greenfly.html
http://www.bristol.ac.uk/news/2016/april/polarization-greenfly.html

 

[damaged]

Not lost a crop to bydv when in organic system. If susceptibility is a issue caused by spraying then your own observations would fit. If protection from bydv is from the bigger picture of rotation , soil biology and fertility (both soil and plant) then moving to pre em only may not necessarily protect.

I noted on a previous thread bydv hit my dd fields and not the ploughed ones adjacent ( all on the conventional block.) however only one seasons observations.

 

[Richard III]

I think @York would tell you that unbalanced nutrition in the plant will allow aphids to breed faster. That could be induced by excess N due to cultivating, or messing the plant up with herbicides IMO. Probably just a part of the reason why there is usually much less BYDV in a No Till field.

Would you expect BYDV in a November sown crop? I would have thought aphid migration would have been pretty well over by the time the crop was up, even last year?

I have got some BYDV showing here now, there are a couple of headlands fairly badly affected and a few patches here and there in some fields, not enough to wish I'd sprayed though. It is only september sown wheat that is affected, however where I sowed on the green in september is completely clear.

 

[Dockers]

Dan Powell, No pre em, !!!!!

Crystal is flufenaset, plus Pendimethalin. plus you added DFF..
That is a pretty hefty pre em in my book !

 

[shakerator]

My usual strategy here for autumn cereals is no pre-em apart from glyphosate and then pendimethalin (eg Crystal) + DFF at 1 leaf with some manganese and an insecticide if necessary. No black grass here...

Now here is a theory based on observation.

No BYDV in November sown wheat where ploughed. Also no herbicide used on said crop until spring.

Worse BYDV in one area of barley where double dosed with spray due to tractor PTO stopping and me not knowing exactly where it had happened.

Anecdotal evidence of no BYDV from other no till farms (@SilliamWhale , @Clive) where the strategy was pre-em and shut the gate.

So the question is: do leaf applied herbicides stress the crop and therefore make it more susceptible to disease e.g. BYDV and therefore would I be better off doing a pre-em in future?

would certainly dewax the plant.

but my main issues are from green bridge.

manure use also seems to attract aphids

 

[Dan Powell]

Dan Powell, No pre em, !!!!!

Crystal is flufenaset, plus Pendimethalin. plus you added DFF..
That is a pretty hefty pre em in my book !

That was applied post-em at 1 leaf.

 

[Dan Powell]

would certainly dewax the plant.

but my main issues are from green bridge.

manure use also seems to attract aphids

Best winter barley had manure, but it was black like compost.

I now apparently have bydv in all my spring barley too. Green bridge is the likely suspect here, and it all had 8t/acre FYM too.

This year is proving to be a disaster...

 

[Simon C]

I have loads of BYDV in unsprayed wheat this year, so unfortunately long term no-till in no defense against aphids or the virus. The only observation I would make is that it always comes from a neighboring bit of permanent grass so whether I have a green bridge actually in the field makes no difference. I have one field of wheat where there is a grass paddock on it's east side, divided by large hedge, but where there is a 30 yard gap in the hegde, you can clearly see that a rare Easterly wind had blown the aphids and virus across the field.

Another strange thing I found out today when doing a few Brix readings. Most of the wheat still has pretty low sugar levels, 5 or 6%, but all the BYDV patches are around 17% which is way higher than you would ever expect to get in very healthy crop. Can understand that at all.

 

[shakerator]

I have loads of BYDV in unsprayed wheat this year, so unfortunately long term no-till in no defense against aphids or the virus. The only observation I would make is that it always comes from a neighboring bit of permanent grass so whether I have a green bridge actually in the field makes no difference. I have one field of wheat where there is a grass paddock on it's east side, divided by large hedge, but where there is a 30 yard gap in the hegde, you can clearly see that a rare Easterly wind had blown the aphids and virus across the field.

Another strange thing I found out today when doing a few Brix readings. Most of the wheat still has pretty low sugar levels, 5 or 6%, but all the BYDV patches are around 17% which is way higher than you would ever expect to get in very healthy crop. Can understand that at all.

Simon
The reason this happens is that sugars get trapped in the leaf at the expense of future growth . Try a snap test on the leaves to prove it...

 

[shakerator]

Best winter barley had manure, but it was black like compost.

I now apparently have bydv in all my spring barley too. Green bridge is the likely suspect here, and it all had 8t/acre FYM too.

This year is proving to be a disaster...

Yep I have it in spring barley and oats

 

[SilliamWhale]

I think I've been lucky that's all though, I do have a bit of burn not much.

I don't think I'd expect no till to encourage or discourage bydv

 

[Dan Powell]

I think I've been lucky that's all though, I do have a bit of burn not much.

I don't think I'd expect no till to encourage or discourage bydv

A lot of historic work done shows that later drilled spring barley is more affected by bydv because aphid activity increases as temperatures improve and less developed plants are more susceptible. The old timers (pre insecticides) would sow spring corn on a frost tilth.

This implies no till more vulnerable in high pressure years as later drilling is the norm?

 

[Doctor who]

Always seen BYDV (in a bad year) associated with higher herbicide loadings in plots.
Aphids work on green spectrum and are attracted to paler greens.
More herbicide, paler green
No til paler green due to reduced N mineralisation