Field bindweed, Convolvulus arvensis L. (Convolvulaceae) is one of the most aggressive, perennial weeds of grain producing areas of North America. To control this weed, the leaf galling mite, Aceria malherbae Nuzzaci (Acari: Eriophyidae) has been utilized. The phenology and spatial distribution of the mite were followed for several years (2000 - 2004) in central Montana. Stems emerged late in May and continued to emerge until mid-July. Thereafter, numbers generally declined due to senescence caused by dry conditions. In contrast, the number and percent of infested stems increased during the summer. Approximately 20 to 27% of stems were infested in early spring. By late August between 39 and 62% of the remaining stems were infested. No significant declines in stem densities were observed; although densities varied within the season, as well as among years, depending upon moisture. Greater numbers of galls were observed in the upper stem crown. Mite populations increased during the season, peaked in July and then decreased though the remaining growing season. Both bindweed stems and infested stems were weakly spatially aggregated within plots and weak associations between stem densities and the presence of infested stems were also noted. These associations did not necessarily reflect the intensity of the mite infestation.