In this month’s Crop Walk and Talk, Russell Dean, agronomist with Frontier Agriculture, highlights the agronomic issues affecting wheat, barley and oilseed rape crops near Blandford Forum, Dorset. Abby Kellett reports.
Crop growth had accelerated from where it was a few weeks ago, bringing about new threats to crop yield and quality.
Given recent warm weather, wheat at the site had rapidly moved through its growth stages. In the most forward crops, the flag leaf was fully emerged, marking the T2 timing, which Frontier Agriculture’s Russell Dean described as particularly important.
“The flag leaf contributes 50 per cent of the total crop yield, so it is important to keep this leaf clean. If farmers have not yet applied the T2, and where flag leaves are fully emerged, they should be doing so now.”
High septoria pressure has been a recurring theme this season and this was no different in the South West, where conditions have been ideally suited to the disease.
Active septoria was present on the lower leaves of most plants. Given recent rainfall, Mr Dean warned of the potential for further infection where leaves have not been protected.
“There is plenty of septoria on leaf five and it is active. Because we have had a lot of rainfall, my concern is septoria will have splashed up the plant.
“So even though we cannot see septoria on upper leaves, it is really important we use a robust rate of SDHIs, a triazole and possibly some chlorothalonil to protect upper leaves from septoria moving up the plant.”
Although yellow rust and mildew were not abundant at this particular site, infections have been common among susceptible varieties.
“This year, yellow rust has been a big problem further east, but even in the South West, it has been seen a lot in varieties such as Reflection.
“Another disease we have been troubled by is mildew on varieties such as Leeds. Where this is a problem, I would advise adding a mildewcide in with the T2 where it has not already been applied.”
While the opportunity for grass-weed control has passed, Mr Dean suggested making a note of highly infested areas so they can be targeted post-harvest.
“In this field, we have some sterile brome which has encroached in from the headland. It can be helpful to map these areas for future reference and you can use software to do this.”
There is still time to control problematic broad leaf weeds such as cleavers, which can negatively affect yield, according to Mr Dean. He recommended the addition of Fluroxypyr to the T2 tank mix, if these weeds are at high populations.
Milling wheat growers should be focusing their attention on achieving protein specifications, a factor which can be largely influenced in coming weeks.
He said: “In terms of nutrition, all nitrogen should now be applied to feed wheats. However, for milling wheats, which represent about one-third of the wheat area in the UK, farmers should be focused on achieving the 13 per cent protein.
“This can be achieved using foliar nitrogen products from the end of flowering to the milky ripe stage.”
As with wheat crops, the T2, which consisted of an SDHI and a triazole, had already been applied at this site. Barley crops will require no further input, according to Mr Dean.
The crop appeared clean, however barley yellow dwarf virus (BYDV) was prevalent in some locations, he said.
“One of the big problems in the South this year has been BYDV, caused by the mild winter when aphids continued to spread into the crop.
“Even crops which were treated with an insecticide on the seed and had a follow-up insecticide in autumn have been affected and are suffering from stunted growth and yellow tips.”
Where farmers were unable to get onto crops in autumn to apply an insecticide, BYDV damage is likely to be even greater, said Mr Dean, who believes growers can expect a noticeable impact on crop yield and quality where BYDV is present.
“We have not had BYDV damage like this for many years. Unfortunately, it will damage yield as well as grain size and weight. It has also been a problem in wheat and oats.”
On assessment, spring barley crops had grown rapidly, having just reached stem extension. This is despite reports of poor rooting of some spring crops. However, it was suspected this problem would likely be limited to heavy soil types.
OSR was identified as being at the late flowering stage and pods were starting to set on the main stem.
While pollen beetle is now considered a beneficiary in terms of crop pollination, seed weevil posed a new pest threat.
Mr Dean said: “Seed weevil can be damaging to the OSR crop, as they burrow holes into pods then the pod midge can lay its eggs into the holes the seed weevil makes.
“If you find more than one per plant, you should consider controlling them with an insecticide such as a pyrethroid.”
As temperatures have warmed, the risk of sclerotinia has also increased. At the site, the combination of falling flower petals along with wet leaves provided a perfect environment for sclerotinia infection, according to Mr Dean.
“Sclerotinia affects OSR as flower petals fall onto wet leaves. This is where the infection will enter the plant.
“If crops have not already received a flowering fungicide, it should be applied soon. If it has received a flowering fungicide more than three weeks ago, it will need a follow up.”
See also: Sclerotinia risk hots up
He acknowledged the extent of light leaf spot damage which has been reported this season. While the disease is normally associated with northern regions, this year it has been seen throughout crops in the South West.
Mr Dean recommended using a fungicide aimed at controlling light leaf spot within the tank mix if the disease is still present on upper leaves.
“If your crop is still suffering from light leaf spot, it may be advantageous to include a product such as prothioconazole in with your flowering spray.”
Recently, there has been an upturn in OSR values, rising some £30/tonne from this time last year, according to Mr Dean, who suggested late foliar nitrogen would be beneficial in helping maximise crop yields.
“Many farmers may have been tempted to reduce nitrogen applications, perhaps because the crop’s green area indexes were high earlier in the campaign.
“It is now too late to apply solid nitrogen to OSR. However, foliar nitrogen products, such as Oilseed Extra, can be applied at the end of petal fall.
“We have seen foliar applications increase yields by about half-a-tonne/hectare, even where normal nitrogen programmes had already been applied.”