June 23 (UPI) -- Though antibiotics have been used for decades to combat bacterial diseases among various crop varieties, including apples and pears, the practice isn't closely monitored.
New research -- published Tuesday in the journal CABI Agriculture and Bioscience -- suggests the use of antibiotics on crops is more widespread than previously suspected.
For the study, scientists surveyed how antibiotic usage is tracked in 158 countries. Though more than a quarter of the surveyed countries have developed antibiotic monitoring programs for human use and animal health, just 3 percent currently track antibiotic use on crops.
To get a better sense of how frequently antibiotics are deployed against crop pathogens, researchers analyzed 36,000 records collected at Plantwise plant clinics in 32 countries between 2012 and 2018.
Plantwise is a global program created by CABI, the Center for Agriculture and Bioscience International, to help small-scale and family farmers sustainably combat crop pests and diseases.
The analysis revealed antibiotic applications are recommended for more than 100 crops, sometimes in large amounts and for non-bacterial pathogens. The data showed that in Southeast Asia, an average of 63 tons of streptomycin and 7 tons of tetracycline are sprayed on rice crops each year.
Most application recommendations call for the use of antibiotics against bacteria pathogens. In some places, however, antibiotics are being prescribed for other kinds of crop diseases, for which the treatment will have no effect.
"There is a considerable proportion of crop advisors recommending antibiotics against insect pests -- either the advisors are unaware that they will have no impact on insect pests, or they are recommending antibiotics as a preventative measure against bacterial diseases," Philip Taylor, lead study author and CABI researcher, said in a news release.
Records showed 11 antibiotics -- frequently, blended together -- are commonly applied to crops on farms throughout the Americas, Eastern Mediterranean, Southeast Asia and the Pacific Rim nations. The ratios in antibiotic mixtures and the recommended amounts varied from country to country, region to region. Researchers found little evidence of antibiotic use on crops in Africa.
"It is very interesting that there are no records from Africa," Taylor said. "You may suspect that this was due to price, yet that does not appear to be the reason."
Though the amounts of antibiotics deployed on crops pales in comparison to the amounts used for human and animal health, research suggests bacteria strains developed antibiotic resistance up to 100,000 times faster when exposed to antibiotics in combination with other agricultural chemicals.
Authors of the latest report suggest antibiotic use on crops warrants further study, as it could provide a new avenue for bacteria strains to develop antibiotic resistance in humans.
"Some evidence suggests that crops are a potential vehicle for resistant bacteria to enter the human gut, and is an area where further research is needed," Taylor said. "It is hoped that the data presented in this paper will increase the debate regarding the use of antibiotics against crop pathogens and that crop production will be included under the one health umbrella."