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Weed control in winter barley and assessing aphid populations to control BYDV

Planting so far this year is slower than many would like as the weather has not been as kind as last year. Michael Hennessy, Head of Teagasc Crops Knowledge Transfer, writes about weed control in winter barley and assessing aphid populations to control BYDV.

The progress so far has been reasonably good towards the Northeast however less progress has been made in the south and southeast of the country. Plough based systems are probably most optimal for planting at the moment as most people are ploughing directly in front of a one past system. Non plough based systems tend to like drier conditions where soils are relatively dry on top but also dry down though the profile.  

As we are now entering the second half of October and growers should revaluate their seeding rate as soil conditions continue to deteriorate. Planting crop into a colder and/or wetter seedbed will inevitably lead to a lower establishment rate therefore more seed is needed to achieve the same plant stand.   

Keep an eye on the seed size of the crop you are planting as many varieties have bigger seed this year than other years. Many varieties can often have a thousand grain weight of over 55 grams. For crops sown this week an establishment rate of 80% should be expected.  At the moment, in reasonable conditions, planting Graham (TGW 60g) to achieve a plant count of 270 plants per meter squared, would require a seeding rate of 203 kgs per hectare (or 12.9 st/ac)

This broken weather forces growers to keep the planting within the available weather windows which leaves little time for other jobs. In last weeks Teagasc daily tillage article we spoke quite a bit about the importance of applying a pre-emergence herbicide to control problematic weeds especially grass weeds in winter barley. Where this pre-emergence herbicide is missed it is more difficult to control grass weeds such as annual meadow grass and more specifically brome especially in Winter barley.   

The ideal timing is to apply a pre-emergence herbicide to winter barley up to 48 Hours post sowing. If you were delayed in applying a pre-emergence herbicides to winter barley then some caution is needed as to the exact growth stage of the barley at the time of application. Avoid applying herbicides to Winter barley when the crops is at the peri-emerge stage (when the barley is about to push through the surface of the soil) as barley is quite soft and vulnerable at this growth stage.  Products containing prosulfrocarb can be particularly damaging if applied at this stage. 

Consult your Teagasc advisor or agronomist for the best herbicide options if you find yourself in the situation.

The earliest planted crops are now at the one to two leaf stage and are getting close to the ideal stage to apply an insecticide to control aphids which transmits BYDV. The first thing to do is to check is to see if aphids are present in the crop.  Early sown crops i.e. September sown generally require one application with a follow up in November. For crops sown in October only one application should be needed and for crops emerging in November no insecticide should be needed however with all of these recommendations a grower must not only inspect the crop before the insecticide is applied but also a follow-up inspection four to five days later to see how well the insecticide has worked.

Dr Louise McNamara, an entomologist from Oak Park, joins Michael Hennessy on this week’s Tillage Edge podcast to discuss and advise on the threat posed by aphids this year.

Find out more information and advice from the Teagasc Crops team here. Find your local Teagasc office here