Low host-plant nitrogen contributes to poor performance of heather beetle, an introduced weed biocontrol agent in New Zealand

Low nitrogen levels in heather plants likely explain the poor performance of the introduced heather beetle, an intended biocontrol agent for non-native heather in Tongariro National Park (TNP), New Zealand. The study found that heather in TNP has significantly lower nitrogen content (1.14% dry weight) compared to European samples (1.48%), a difference attributed to New Zealand's low air pollution and infertile soils. Fertilizing heather in controlled experiments increased its nitrogen levels, which in turn boosted beetle oviposition by 35% and adult body mass by 28%. Field trials from 2001 to 2015 further confirmed improved beetle performance on fertilized plots. These findings suggest that host-plant quality, specifically nitrogen content, may be a critical but understudied factor in the success of weed biocontrol agents.

Peterson, P., Fowler, S. V., & Barrett, D. P. (2024). Low host-plant nitrogen contributes to poor performance of heather beetle, an introduced weed biocontrol agent in New Zealand. Biological Control, 197, 105589. https://doi.org/10.1016/j.biocontrol.2024.105589