Agrovista agronomist Craig Green will be using a new fungicide in his potato blight programmes this season
Blight spray programmes and T3 focus
Agrovista agronomist Craig Green will be using a new fungicide in his potato blight programmes this season and plans for wheat T3s and OSR desiccation are also taking shape.
Given the recent warm weather, moisture and the presence of blight on some seed stocks, good fungicide programmes will be important from the rosette stage onwards in potato crops, says Craig.
He’ll kick off the blight programme with Ranman Top (cyazofamid) at 0.5-litres/ha to keep out foliar blight and control early zoospore activity in the soil.
A varied sequence of products will follow during rapid canopy management to reduce selection for resistance. He’ll include a new arrival for this season from Syngenta, Carial Flex (cymoxanil + mandipropamid).
“It is a really excellent product for foliar blight,” says Craig. “It topped the Euroblight rating table for 2015 with a score of 4.4, and tackles the newer, more aggressive strains of blight that can occur earlier in the season at cooler temperatures.”
Carial Flex contains mandipropamid, a strong protectant, and cymoxanil, which provides good kickback. The water dispersible granule formulation rapidly dissolves in the spray tank, he adds.
“It’s the first time we’ve seen these two actives as a co-formulation. The product will build flexibility into the blight programme and I’ll alternate it with other translaminar/systemic products to provide the best protection during rapid canopy growth.”
Carial Flex should be applied at 0.6kg/ha in 200-600 litres/ha of water depending on haulm density, and can be used up to six times per crop between 1 May-31 August, says Craig.
He’ll add foliar nitrogen to blight sprays as Krypton N at 1-5-litres/ha depending on haulm size. “It promotes healthy leaf growth and helps repair leaf damage, providing a pep up when growth is at its most rapid, increasing the plant’s own defence against blight.”
Wheat ear sprays
As T2 sprays draw to a close, attention will be turning to T3 ear sprays, applied during flowering to control fusarium/michrodochuim ear blight and suppress any surviving septoria on the flag leaf.
The main target at T3 is ear blight, so sprays need to be applied as soon as the ear is fully emerged but before flowering, when the threat diminishes, says Agrovista agronomist Craig Green.
“Most growers will have used strobilurins and SDHIs in the mix at T1 and T2, so they won’t be able to use them again. Septoria continues to lurk, especially but not only in crops that missed a T0.
“We’ve had enough rain to keep it moving up the plant, so we’ll need a good protectant. But the main target is ear blight, so we need to be applying a spray as soon as the ear is fully emerged but before flowering, when the threat diminishes.”
Craig favours prochloraz + tebuconazole (as in Monkey), though prothioconazole is a good alternative. “Both are protectants so need to be applied before any infection occurs.”
Wheat prices may be low but he urges growers to treat crops if a wet spell during flowering is forecast. “It only takes one rainfall event during flowering to greatly increase the risk of infection. Just one rejected lorry-load will far outweigh the cost of a T3, whether feed wheat or milling.”
Most oilseed rape crops are even this season and will suit desiccation with glyphosate. Lodged crops hinder chemical translocation so should be sprayed with diquat + pod sealant instead, says Craig.
“Glyphosate does a more thorough job and the desiccated crop tends to be less brittle – seed weevil/pod midge has been a problem in some fields so pods might be more fragile than usual.
“The cost of glyphosate has fallen recently so it’s worth buying ahead before new stocks hit the market.
“I’ll use Companion Gold at 1-litre/ha with glyphosate – it is more cost effective than proprietary pod sealants, helps reduce drift and helps spread the droplets across and into the crop, resulting in a more even kill.”
Watch out for midge
A few days prior to T3, at mid ear emergence (GS53-59), growers should monitor crops of susceptible wheat varieties for orange wheat blossom midge.
“Heed the thresholds and only spray if these are exceeded – over one midge per three ears in feed wheat and over one in six for milling and seed crops,” Craig advises.
“The best time to check is mid-evening when temperatures are above 150C. Agrovista advises lambda-cyhalothrin (eg Hallmark Zeon) or thiacloprid (eg Biscaya), to minimise the effect on non-target organisms. Once the crops starts to flower, the danger period is past.”
Further details can be found at http://www.hgca.com/media/183701/g45-orange-wheat-blossom-midge-guidelines-for-assessment-and-control.pdf
*Craig Green is an agronomist with Agrovista, based at Great Ellingham, Norfolk ([email protected]).