It’s time to take grassweed biosecurity seriously

Over the past decade, a lot of effort has been made to encourage the adoption of integrated pest management (IPM) on farms. The main drivers of this management approach were the continued evolution of our key pests and diseases, policy push-factors from the EU, withdrawal of key actives from EU markets and a narrowing pipeline of new actives coming on the market.

In the next decade, these factors will only intensify and thus, our understanding and utilisation of IPM principles must step up to the mark. When it comes to weed control on farms, many IPM measures are generally accepted as standard now and in many cases, are just regarded as good farming practice.

Listen to "It's time to take grassweed biosecurity on tillage farms seriously" on Spreaker.

However, the spread of difficult to control grassweeds such brome species, wild oats, canary grass and blackgrass are still increasing. For example, according to Teagasc, there are now over 40 confirmed cases of blackgrass reported on Irish farms. However, it is accepted that the number of unreported cases is likely to be more than this.

Blackgrass has traditionally been seen as a UK problem, where 98% of the sampled population there is now resistant to at least one herbicide group.

However, we now have confirmed cases of the weed in fields in counties Louth, Meath, Wexford, Waterford, Laois, Kildare and Dublin, as well as Cork and Tipperary. It is feared that some of these plants could be resistant strains found in the UK. Therefore, blackgrass is now an Irish problem too.

Last week, I attended a grassweed workshop in Donegal, hosted by Teagasc tillage advisor Martin McCullough. It was broadly agreed by the participants that one aspect of IPM that doesn’t receive enough attention is in the area of biosecurity.

Just like a livestock farmer trying to keep their herd disease free, biosecurity measures need to be put in place to prevent the infection and spread of a biological threat. Tillage farms are no different when it comes to grassweeds and it’s time we, as an industry, took weed biosecurity seriously.

Biosecurity measures can be broken down into three main categories; prevention, control at source and stopping the spread. I spoke with Teagasc crop specialist Shay Phelan and Enable Conservation Tillage project manager Jimmy Staples about these measures at last week’s walk. The full podcasts are available online.

Prevention

Preventing grassweed seeds from entering your farm is the frontline defence for any tillage farmer. Resistant blackgrass seeds are thought to have entered Irish farms via machinery, straw and occasionally seed imported from the UK.

That was certainly the case in 2018, when increased volumes of UK straw was imported into Ireland. Work from the AHDB shows that the amount of weed seed retained at harvest time in straw varies between host crop and grass species. The figure is low for blackgrass in wheat, between 2% and 20%, but rises to 50% in winter barley. Generally, bromes retain more seed, with rye grasses retaining as much as 70%, even in wheat.

However, now that populations are established in Irish fields, seeds are much more likely to spread from farm to farm. This doesn’t just apply to blackgrass seeds.

Research presented at this year’s national tillage conference by Ronan Byrne found that resistant wild oat populations sampled in Wexford tended to be clustered.

This indicated that resistant seeds spread throughout the farming network via machinery, straw, grain and natural migration.

Therefore to combat this, tillage farmers will need to start asking the awkward questions about the origins of their machinery and inputs.

If machinery is sourced from an area of known grassweed infection, then that machine needs to be thoroughly cleaned before delivery. The same may have to apply to contractors’ machinery, if working in a high-risk area.

If you suspect that weed seeds may be present in organic manures which must be spread, aim to apply it on grassland. Grassweeds will generally struggle to compete with established grassland.

Control at source

Never adopt a wait-and-see approach when it comes to grassweeds. A small problem can become a large problem very quickly. Therefore, scouting for weeds regularly is important. However, having the knowledge to properly identify them is key. Growers need to understand the weed’s life cycle and if herbicide-resistant populations are in the area.

Adopt a zero-tolerance policy for problematic weeds in an effort to prevent seed return, which often means taking action when first identified. This won’t necessarily mean chemical control, as options are often limited and sometimes not warranted.

Hand rogueing is very much an option for small populations of grassweeds. Ensure that you pull the entire plant and place it in bag when walking though the field. Mowing, baling and removing the infected area may be an option for severe infestations.

Stop the spread

Once present on your farm, you have a duty to prevent the further spread of grassweed seeds to other fields and farms. Regular and strict machinery hygiene, especially during high-risk periods for seed spread, is crucial.

All machines carry the risk of spreading seeds, not just combines and balers. Weed seeds can gather on axles, mudguards, rims, steps and many more locations. Try to leave field work in known infected areas until last. This will allow you to inspect and clean down your machinery after the job.

While this seems straightforward on paper, it may not always be easy or practical to do in real life. However, machinery contamination is undoubtedly contributing to the spread of grassweed seeds and it likely won’t stop until we take machinery hygiene seriously.

If you’re transporting grain from infected fields, don’t fill the trailers fully, as this may allow grassweeds seeds to blow from the trailer in transit.

Remember that you can be a source of transmission too, so check your boots and clothes for grassweeds seeds after exiting an infected field.