A new study analyzing data on genetically modified Bt corn has found “little impact on nontarget insects and other organisms, especially compared to growing conventional corn,” USDA's Agricultural Research Service said Monday.

“Bt corn represents a highly selective pest control technology with relatively few negative consequences for non-target invertebrates, especially when compared with the use of broad-spectrum insecticides for managing Bt-targeted pests, according to the scientists,” ARS said.

ARS said it was “the largest, highest quality analysis of data ever conducted” on the subject and “largely proved out previous individual studies.” However, “critics have been suggesting” that in addition to controlling pests such as European corn borers and corn rootworms, it also can destroy beneficial insects or other non-targeted organisms.

The study was published Monday in Environmental Evidence

"The effects of Bt maize on the community of non-target invertebrates inhabiting maize fields were small and mostly neutral, especially when compared with the effects of broad-spectrum pyrethroid insecticide treatments," the authors concluded.

The paper’s meta-analysis of other studies “showed Bt corn had no negative effects on most invertebrate groups including ladybeetles, flower bugs, and lacewings. However, populations of Braconidae insects  — parasitoid wasps that prey on corn borers — were reduced with Bt corn."

“One of the issues with assessments of possible nontarget organism damage by Bt corn has been that each study was limited in scope, environment or size,” ARS said. “The paper's three authors have made up for these shortfalls by systematically pulling together data from studies in 12 bibliographic databases, 17 specialized webpages, and the reference sections of 78 review articles that all met the highest standards for research quality.”

All told, the database contains more than 7,200 records from 233 experiments and 120 articles, the authors noted in the study. 

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"We gathered together hundreds of individual studies published between 1997 to 2020 that have looked at whether growing Bt corn changed the environmental abundance of non-target animals such as arthropods, earthworms and nematodes, especially as compared to growing non-genetically modified corn accompanied by the pesticide necessary to control major pests," said ARS entomologist Steve Naranjo, director of the Arid-Lands Agricultural Research Center in Maricopa, Arizona, and one of the authors of the study.

Other authors are with Agroscope, ARS’s Swiss counterpart.

A spokesperson for the Xerces Society, an invertebrate conservation nonprofit organization, did not immediately respond to a request for comment.

The paper also looked at whether the results of existing studies differed depending on authorship.

"It might be a bit surprising but according to the analysis, when any negative effects by Bt corn on nontarget organisms were found in the data, they were attributed more often in studies with private sector support than when no backing by biotech companies was declared," Agroscope’s Michael Meissle said.

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