In stark contrast to spring 2014 growers across thecountry are reporting crops to be generally clean of disease. This willundoubtedly come as welcome news, but as increasing temperatures raise the riskof disease, what are the implications for fungicide strategies?
It has so far been a kind season; crops are cleanand in good shape, but the evidence of our trials suggest it still pays to getyour protection in first, says KWS product development manager John Miles.
The lower pressure start to spring coupled withlower commodity prices has prompted some growers to consider cutting back onfungicide use in a bid to reduce costs. While perhaps an understandablereaction Mr Miles warns that disease is no respecter of the commercialpressures facing growers.
We all realise pressure will soon begin tointensify. There is a desire to save on inputs, but if growers plan to changetheir strategy on the back of current conditions they need to be aware of theimplications should the situation deteriorate.
The results of long-term trials demonstrate that evenin low pressure years, there is a clear payback to be had from following acomprehensive fungicide programme.
Mr Miles was speaking at a recent agronomy briefingheld in conjunction with BASF and Prime Agriculture to consider how learningsin plant disease resistance could be used to inform fungicide programmes.Although not a replacement for fungicide applications, he said resistanceratings could be used to determine the order in which crops were to be treated,but with the caveat that this is highly dependent on drilling date and diseasepressure.
2014 presented ideal conditions to investigate thecontribution disease scores make to combatting Septoria tritici. In atypical year, measuring the differences between a variety with a Septoria scoreof 4 and one with 6 is quite difficult and often masked by other diseases suchas rusts. Less than four or more than 6 is, in contrast, quite easy, but mostvarieties fall in to the first category so it is important to know how thesewill react to pressure, he said.
Perhaps not surprisingly the crops receiving morerobust programmes performed better, but the difference in programmes was stark.
Visually, there was little difference betweencrops, but those that received a second SDHI and a higher rate ofchlorothalonil were able to better utilise the applied nitrogen. As a result weobserved an average yield increase of more than 0.75t/ha for a regime applying280kg N/ha.
His observations were supported by BASF regionalsales manager Steve Dennis who explained that the yield differential betweentreated and untreated crops in trials was greater than the long-term average.
There is always a strong response to fungicides, butthe margin narrows as you move to those with better disease ratings. Forexample, Gallant, with a Septoria rating of 4, showed a 5.0t/ha response tofungicides in our trials while Cougar, with a rating of 7, gave a response of3.3t/ha.
The average response across 30 varieties in 2014was 4.39t/ha. At a wheat price of 110/t that is an extra 483/ha in output. Ata fungicide cost of 114/ha that is a MOIC of 369/ha, equivalent to 4:1return. Across 200ha that is an extra 73,860 so there is a compelling argumentfor not skimping on control.
If viewed in isolation however, response tofungicides as a single measure could be considered misleading. It isimportant to look at output. Varieties with lower resistance ratings tend toshow the greatest response, but not all yield to the same level.
This is partly explained by linkage drag saidKWSs John Miles. No one truly understands how Septoria resistance worksthough we are learning all the time, but we have observed lower yields inplants demonstrating higher levels of resistance. Overcoming this linkagedrag is the subject of research at the highest level, he said.
According to Steve Dennis, the analysis does notprovide a basis for dropping those varieties with relatively poor scores, butrather supports the case for managing them accordingly to meet potential.
On average margin increases by 22% so there is abenefit from choosing a cleaner variety, but varieties with recognised highyield potential will always respond. Horatio and KWS Kielder, for example haveSeptoria ratings of 4 and 5 respectively, but yielded close to Revelation andSkyfall, both of which have a score of 6, said Steve Dennis.
For Prime Agriculture agronomist Philip Simons,disease ratings are coming to be seen as an increasingly useful management toolamong his clients.
There is certainly a desire among growers to adoptvarieties with better resistance. About a quarter of the Prime portfolio isdown to varieties with a rating of 4.
It fits with wider economic and environmentalpressures. There is a desire to make the most of the plants natural resistanceto disease, buy some time when conditions make application difficult andprolong the life of the plant protection products we have, he said.
But equally there was recognition that rates neededto be maintained and the best products used. You cant afford to skimp onprogrammes. Responses will follow, but rate, interval and product choice areimportant to maximising that response, he added.
BASF 2014Fungicide programme
T0: Opus Team 0.5l/ha
T1: Tracker+Bravo 1.5+1l/ha
T2: Adexar+Bravo 1.5+1l/ha
T3: Proline 0.54l/ha
Cost: About 114/ha