Public expectations around herbicide use are likely to become more difficult to manage, Mark Congreve, a consultant with the Independent Consultants Australia Network (ICAN), told delegates at the 2019 Australian Summer Grains Conference.
Speaking about the future of chemical use in Australia, Mr Congreve said legal and political decisions, not scientific ones, could start to influence their use.
For example, regulatory agencies around the world continue to find the use of glyphosate to be acceptable, when used in accordance with the product label.
However, a 2015 decision by the International Agency for Research on Cancer to list glyphosate as a probable carcinogen - at group 2A level - has triggered a number of lawsuits in the United States, with the first test case in Australia also recently starting in Victoria.
While Mr Congreve said that this group 2A classification also included activities such as red meat consumption and shift work as similar possible carcinogens, it still had connotations for the consumer.
In the same vein, some consumers might decide they do not want any trace of pesticides in their food.
This could be regardless of what regulators assess as being safe for consumption, he said, mentioning the rise in DIY kits available online that test for residues.
Exporters, too, may require different maximum residue limits (MRLs) depending on the levels set by importing countries.
"Labelled pesticide use patterns may contain trace levels of pesticides in produce that do not exceed the Australian MRL, but may exceed other countries' import tolerances (where these are lower than the Australian MRL)," Mr Congreve said.
"We will need to be more aware of this. The European Union, for example, has withdrawn many pesticides over recent years and may require no detectable residues of these pesticides in any imported produce."
Mr Congreve also spoke about how increased automation may be used in combating individual weeds and the challenge that climate change will have on herbicide chemistry.
"Climate change will impact on chemical use," he said.
"There will be a change in where we grow summer crops, faster insect cycles and less spraying opportunities - because there will be less optimal hours to put out pesticide sprays."
Mr Congreve also said the impact on hydrophilic (water loving) herbicides could see the need to apply higher application rates under hotter application conditions. With glyphosate, for example, less herbicide can penetrate the leaf as temperatures increase.
On a positive note, however, he said the agricultural industry had some great stories to tell, which could help with public perceptions of farming.
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