Insecticides under review: What does it mean for winter cereals?

A vote is expected to take place on the future of neonicotinoids – the most widely-used insecticide in the world – in the new year.

EU member states have been discussing the future of neonicotinoids at a meeting of the European Commission Standing Committee on Plants, Animals, Food and Feed (SCOPAFF) this week.

The meeting began yesterday (December 12) and will conclude today (December 13). A vote was expected to take place on a ban of the use of these products in greenhouses and on winter cereals. This is now delayed and will take place in the new year.

As no deadline is looming on the vote, it is difficult to say when the plenary vote on the Committee of Agriculture and Rural Development’s (COMAGRI’s) report – ‘Prospects and Challenges for the EU Apiculture Sector’ – will take place.

A ban on the use of three neonicotinoids (clothianidin, imidacloprid and thiamethoxam) on sunflower, oilseed rape and maize crops was implemented by the European Commission in 2013. The reason for the ban on these products was to protect honey bees.

The ban did not include the use of these products in greenhouses or on winter cereals. However, further data was requested on the safety of these products and their use in greenhouses and on winter cereals.

The European Food Safety Authority has been compiling a report on the products.

Impact on the Irish tillage sector

Louise McNamara is an entomologist with Teagasc. She outlined the effect that a ban on neonicotinoids and products like Redigo Deter (an insecticide) would have on the Irish tillage sector; particularly on the cereals sector – which has seen increasing levels of Barley Yellow Dwarf Virus (BYDV) in recent years.

The product that Irish farmers will be most familiar with is Redigo Deter – a seed treatment. This seed treatment protects winter cereals against aphids for six-to-eight weeks after sowing. Aphids spread BYDV.

McNamara stated: “If it does go, it will have a huge impact on winter cereals in Ireland – particularly in coastal areas like Co. Cork.

The advantage of the seed treatment is that you’re not dependent on optimum weather conditions for spraying.

“The seed treatment gives you protection so that you’re not as open to the effects of weather variability on spraying conditions – particularly in areas that are most at risk.

Insecticides
Image source: Shane Casey

“Farmers have some flexibility with the spray. If you don’t get in with a spray in November you can still spray up until February and it can help to reduce the yield loss due to BYDV.”

Trial results

BYDV has shown to be a more serious problem on the coast where temperatures are higher.

The table below shows the level of BYDV infection on a winter barley trial site in Co. Carlow and a site in Co. Cork. There are two treatments displayed – a crop sown with a seed dressing and a crop sown without a seed dressing. The level of infection is much higher in Co. Cork – most likely due to milder weather.

Insecticides
Source: Teagasc

BYDV has become a serious problem on tillage farms in Ireland in the past number of years. Aphids have become resistant to some of the pyrethroid-based products currently used for aphid control.

“We don’t know the level of resistant aphids in a field. Teagasc work by Michael Gaffney and Lael Walsh has shown that resistant aphids are widespread.

“This work has been monitoring aphids in all of the major tillage regions in Ireland and testing these aphids for resistance. We will have that data next year.

We have recorded aphid numbers every two weeks on our sites (Co. Carlow and Co. Cork) and we can test those aphids for resistance levels right throughout the season.

The effects of the virus were notably different depending on area. McNamara stated that stunting was observed in plants in Co. Cork, but not in the trial site in Co. Carlow. Teagasc has tested leaf samples of plants for different strains of BYDV.

It should be noted that a new aphicide came on the market this year – Isoclast from Dow AgroSciences – but its use is not cleared for application to winter cereals at this time of the year.

Research work

There is a large amount of work being undertaken by Teagasc on BYDV at present. However, McNamara was keen to stress that the data available at present is only based on one year of trial work. These experiments will now be repeated and this will give more accurate information.

Also Read: Tillage management: How can you control BYDV and aphids?