In Nepal, the gall-inducing eupatorium gall fly (Procecidochares utilis) is deployed as a biological control agent against the invasive weed Ageratina adenophora. A new study by researchers at Tribhuvan University and the Feed the Future Innovation Lab for Integrated Pest Management shows size and abundance of galls induced by the fly are influenced by elevation, knowledge that can help in fine-tuning P. utilis-based biocontrol efforts.