Globe chamomile is considered invasive in the United States in
California and
Arizona. First seen in
Los Angeles and
San Diego in the early 1980s, it heavily infests the counties between those cities. It expanded its range to the
Phoenix area in the first decade of the 2000s and can be found in
Maricopa,
Pinal, and
Pima counties. Rapid spread in Maricopa County occurred due to above-average fall and winter precipitation in 2016, and 2018–2020. Heavy infestations occurred in northern parts of
Phoenix and
Scottsdale as well as to the south along the
I-10 corridor towards
Casa Grande. The first recorded growth in
Tucson was in 2015. The plant can be removed physically or killed with
triclopyr; it is resistant to
glyphosate-based herbicides. The Arizona department of Agriculture considers it a "high priority pest for quarantine, control or mitigation if a significant threat to a crop, commodity, or habitat is known to exist." Other problems are its density which displaces native vegetation, the high flammability of dried-out patches, and the caustic smoke produced when it burns. ==Conservation status==