Trepidation remains in the tillage sector over how to manage with less pesticides

The Farm to Fork strategy also requires a 50% reduction in the use of more hazardous pesticides (chemicals that are candidates for substitution).

“Ireland has its own unique climate, with its own distinct pest challenges. What could happen in countries within similar climatic zones wouldn’t necessarily mimic what we would experience here,” said Meghan England.

Ms England is a postdoctoral researcher working in this area with Teagasc. Meghan conducted an extensive review of scientific papers on pesticide reduction.

Her colleague, Robert McDougall, undertook a survey to estimate the impact in Ireland of achieving the EU pesticide reduction targets while employing current typical crop management techniques. They revealed their findings in a recent Tillage Edge Podcast.

According to Robert, the good news is that Ireland has more or less already achieved the EU’s Farm to Fork strategy target to reduce total pesticide use by 50% by 2030.

Nevertheless, there seems to be considerable trepidation in Irish tillage farming on how to manage with access to much less pesticides in the findings of Robert’s survey

Rather than undertake empirical field research, which would take years, Robert tapped into Ireland’s practical expert knowledge, talking to 17 experts representing a broad sweep of the Irish tillage sector. Responses were anonymous.

“The median predictions we got back from the panel are that, on winter wheat, the reduced use of the hazardous insecticides would reduce yields by around 10%. For fungicides, it was 15%. For herbicides over a 10-year period, it was predicted that the impact would be up to 30%,” Robert said.

"Similar results were obtained for barley, but the impact was less in oats. “Oats are a lot more competitive with weeds,” Robert said.

“Spring crops fared better because they’re not in as much direct competition as winter crops.

“Our damp cool conditions are great for producing high cereal yields, but they’re also great for producing things like fungus.”

Meghan and colleagues reviewed 52 published scientific research papers which addressed the impact of reduced pesticide use on crop income, crop yield, and environmental or social impact.

Large knowledge gap

None of those papers were from Ireland, highlighting the large knowledge gap on the topic in this country. 

“Ireland has its own unique climate, with its own distinct pest challenges. What could happen in countries within similar climatic zones wouldn’t necessarily mimic what we would experience here," Meghan said.

"While there is evidence of yield decline trends with reduced pesticide use, case-by-case investigation is required because of great variability in the research data.

At the 100% pesticide reduction mark, there were individual cases that showed no yield loss and others all the way up to total yield loss

"This means that while we can determine an average figure from this data, such as an average yield loss of 15% when pesticides are reduced by 50%, what this average figure is masking is all that variation that can occur in different scenarios.

"It would totally underestimate the loss for some situations and overestimate it in others," Meghan said.

“The main conclusion from this work is the large knowledge gap in this area, not just for Ireland but other EU member states are in a similar situation.

“From the data that we did get, the findings were — starting with yield — that the majority of results found yield to decrease with pesticide reduction. 85%, in fact, found this.

"The income-related results were more evenly split, with 56% finding income to decrease with pesticide reduction, while 42% actually found it to increase. This can be due to reduced costs by using less pesticides and fluctuating commodity prices.

“For environmental and social outcomes, the majority of results were as we’d expect: They were 73% positive, meaning that they showed there was less environmental harm — such as less toxicity to the environment, less risk to human health, when less pesticides were used."

Greenhouse gas emissions

But negative social and environmental outcomes were estimated in some cases, due to increased use of fuel, because of increased mechanical weeding and cultivation, causing greater greenhouse gas emissions.

“Ultimately, while the data shows us that we can expect to see yield losses as pesticide use reduces, this needs to be investigated on a case-by-case basis at region and crop specific level for policymakers to be able to make the best-informed decisions," Meghan said.

Robert's expert panel was asked what integrated pest management strategies would best mitigate the reduced use of pesticides, in the Irish context. 

“For both managing the impact of reduced fungicide and pesticide use, the most important measure was judged to be the use of resistant varieties of crops — basically a cultivar that can hold off either the fungal pathogens or Barley Yellow Dwarf Virus in the case of insecticides.

For herbicides, the most important technique was considered to be optimised crop rotations. That was also considered very important for managing fungal pathogens

"Two other techniques that showed up in the top three for the three groups of chemicals were changes in sowing date and use of decision support (to help farmers decide where and when to spray, and potentially allow them to spray less pesticide but still get the benefits of controlling the key pests).

“The take home message is that, even with these integrated pest management techniques across the range of crops and seasons and chemical groups that we looked at, the impacts were basically all in the range of five to 20% yield loss for each category," Robert said.