College of Agriculture, Food and Rural Enterprise (CAFRE) advisors are confirming that the wet weather during much of March and April has made crop protection challenging.
As a consequence, crops are under pressure, providing ideal conditions for disease to develop.
An associated factor has been the limited opportunities to get spray and fertiliser applied at the right time.
Growers have been strongly advised to keep an eye on crop growth stages with products and plans in place to spray when the time is right to protect yield potential.
Winter barley disease control
Following a T1 spray at early stem extension, barley will be due its T2 fungicide three to four weeks later.
Growers should target crops when the flag leaf and the first few awns have emerged, according to CAFRE.
Best control of the main yield-robbing barley diseases, rhynchosporium, net blotch and ramularia, is achieved with a mix of active ingredients rather than straight products alone.
In the absence of chlorothalonil, ramularia is difficult to manage, particularly in crops under stress.
Teagasc trials on ramularia show both prothioconazole and mefentrifluconazole perform consistently better than other leading actives when applied on a protective basis.
CAFRE – winter wheat disease control
A well timed T2 fungicide gives a bigger yield response in wheat than any other spray timing.
Growers should apply the appropriate spray mix at growth stage (GS) 39 – flag leaf fully emerged – no later than four weeks after the T1 spray.
AHDB fungicide trials show that active ingredients mefentrifluconazole (Revysol) or fenpicoxamid (Inatreq) give best septoria control and may be worth the extra spend at T2, particularly for high yield potential crops under high disease pressure.
Yellow rust has been a common problem on susceptible varieties in recent seasons. AHDB trials show benzovindiflupyr and prothioconazole (Elatus Era) are particularly effective on yellow rust, but all good mixtures perform well.
To maintain longevity and efficacy of cereal fungicides, it is important you use them responsibly as part of fungicide programmes which minimise the risk of resistant septoria strains developing.
According to CAFRE agronomists, this means following label advice on applications per season.
In other words, only use where necessary, keep up dose rates of actives in mixes and always use in combination with a multisite protectant such as Folpet, which protects other active ingredients in the mix.
Spring crops
A dry February across all of Northern Ireland saw some spring barley sown by early March. However, the persistent rain that followed has meant that the majority of crops were sown considerably later.
For early sown cereals that have not received herbicide, growers should apply a mixture of at least two broad-spectrum chemicals, ideally when weeds are at the two- to four-leaf stage.
Tank mixing a low rate fungicide will prevent disease becoming established and protect yield potential.
Nitrogen can be applied as a top dressing, once tramlines are visible at the two- to three-leaf stage (GS 12-13).
Later sown crops will require the same treatments. However, warmer temperatures and longer day length means they will develop quicker than early sowings. So growers should check regularly to avoid missing key timings.
Protein crops should be inspected for grass weeds and volunteers. If necessary, growers should apply a graminicide (grass weed herbicide) once grasses have emerged and before the crop canopy closes over.
A fungicide is recommended for beans at mid-flowering to control chocolate spot and bean rust.
CAFRE advice on potatoes
Plans should be in place for early weed control in potatoes. Where using pre-emergence herbicides, growers should check regularly to ensure they are applied on time to avoid crop damage.
For later plantings, and taking the shorter growing season into consideration, nitrogen applications should be reduced by 1kg/ha/day past the target planting date.
Careful nitrogen management now will encourage earlier natural senescence and improve the probability of a successful burn down prior to harvest.
In recent seasons, blight sampling has shown a prevalence of the A37_2 strain in Northern Ireland.
This strain has reduced sensitivity to fluazinam (Shirlan), meaning this active can no longer be relied upon for blight control.
With new resistant strains emerging in Europe, potato growers are advised to remain vigilant and submit blight samples for genotype testing to either potato inspectors or CAFRE crops advisers.
