URBANA, Ill., USA – Antibiotic resistance in human and animal health is on the forefront of public debate, but it’s a less well-known issue in plant agriculture. However, antibiotics are important tools in fruit production, and their efficacy hinges on avoiding resistance in disease-causing bacteria.
The U.S. does not currently restrict antibiotics use in fruit orchards, but regulatory measures could occur in the future. A new study from the University of Illinois Urbana-Champaign examines how apple growers might respond to a potential ban on antibiotics and how those responses could affect management decisions and profitability.
“The majority of antibiotics in plant agriculture are used on fire blight in pear and apple orchards. Growers face a dilemma, because they must treat their trees to protect them, but they run the risk of overusing the pesticides, so the disease develops resistance,” said lead author Khashi Ghorbani, doctoral candidate in the Department of Agricultural and Consumer Economics, part of the College of Agricultural, Consumer and Environmental Sciences at Illinois.
Fire blight is a devastating bacterial disease that causes flowers, leaves, and fruit to wilt and die, and it can severely damage affected orchards. Treatment options are limited, but spraying blossoms with an antibiotic such as streptomycin can protect against the disease. Controlling for fire blight is a significant expense; for example, growers spent an average of $250 per acre on preventative sprays during a 2017-18 disease outbreak in Washington State, the country’s premier apple producing state.
“The U.S. already has numerous federal and state restrictions on other pesticides and fungicides, so a ban on streptomycin is quite possible,” said co-author Shadi Atallah, associate professor in ACE.
The researchers developed a dynamic model that evaluates growers’ management decisions regarding antibiotic use when there is uncertainty about whether a ban will be enforced.
Their modeling scenario assumed two types of growers, representing opposite ends of a spectrum. The researchers note that these are extreme positions, and most grower strategies would fall somewhere in the middle.
At one end of the spectrum is the “business as usual” grower, who continues to apply antibiotics at the optimal levels based on a long time horizon, without planning for a future ban.
At the other end of the spectrum is the proactive grower, who would adjust their spraying schedule according to the looming ban. They would increase their antibiotic use to ensure maximum efficiency before the product is no longer available.
Ghorbani and Atallah find that the proactive grower is going to benefit from this strategy if the government does enforce the ban. However, if the ban does not happen, the business-as-usual grower will be better off.
“Imagine that 10 years from now you have adjusted your application according to a potential ban, but it does not materialize. You will be in a situation where you still have access to the pesticide, but the efficacy is not there anymore because you have depleted the resource,” Ghorbani said.
They also looked at whether the value of the crop influences the outcome, as antibiotic efficacy can be considered a non-renewable resource that derives its value from the crop it protects, rather than having intrinsic value.
Indeed, they find that growers of lower-value apple varieties such as Fuji and Gala are more vulnerable to regulatory uncertainty and suffer the most damage from it, while those who grow higher-value varieties such as Honeycrisp are less affected.
“We found that the negative impact for proactive growers diminished as the crop value increased. It underscores that crop choices can have a long-term impact on the economics of the farm, and that higher value crops can help mitigate the uncertainty that comes from policy shifts,” Ghorbani said.
The study presents a hypothetical scenario, but it’s not far from reality, Atallah noted.
“As U.S. administrations come and go, regulatory priorities change, and there is considerable uncertainty regarding policies towards herbicides and pesticides,” he said. “Our model is a planning tool that tells you what would happen under different circumstances.”
The study demonstrates to policymakers how uncertainty affects the decisions of farmers and what the economic and ecological consequences might be. The findings can also illustrate how growers of different apple varieties would need to be compensated for production losses considering their management decisions and possible incentives for their actions.
Ghorbani adds that the study also provides a broader perspective.
“Bringing the issue to the surface will hopefully get people to think about how to ensure optimal antibiotic use for plant agriculture, in addition to human medicine or animal agriculture,” he said.
The paper, “Strategic responses to ban enforcement uncertainty: Antibiotic application decisions in plant agriculture,” is published in the European Review of Agricultural Economics [DOI:10.1093/erae/jbaf068].
Research in the College of ACES is made possible in part by Hatch funding from USDA’s National Institute of Food and Agriculture. This study was also supported by USDA-NIFA under grant number 1023572.