Gall size index (gall diameter length) of the first-generation of Procecidochares utilis on Ageratina adenophora double-galled treatment stems infected and uninfected
with the fungal pathogen Passalora ageratinae. The number of first-generation P. utilis adults (represented by the number of emergence holes) emerging from galls on doublegalled
stems infected and uninfected with the pathogen; from the first release of P. utilis in June 2007. Means followed by the same letter are not significantly different, at
P < 0.05 (t-test). (Mean; box: mean ± SE; Whisker: mean ± 1.96 SE).