The objective of this research was to confirm the identity of the mites associated with the disease known as redberry, and to determine population fluctuations of these species in all phenological stages of three commercial varieties of Rubus spp. The study was conducted in three blackberry plots of the varieties SP-Erandy, X001 (name modified by confidentiality reasons) and Tupy, in the Municipality of Los Reyes de Salgado, Michoacán, Mexico, all subjected to forced production. Monthly samples of all the plant parts present at the successive phenological stages were carried out, starting at the last stage of the polydrupe harvest, which was followed by pruning at grown level, and continuing to the new polydrupe harvest. Plant parts were carefully dissected to recover the eriophyoid mites, mostly inside vegetative and reproductive buds, internodes and fruits. Representative specimens of what seemed morphospecies were mounted in slides or on metal stubs for observation with phase contrast or scanning electron microscope, respectively. Adult females present in each morphological structure, for each variety and sampling date, were counted and their populations were compared among varieties using ANOVA and multiple comparison test of means (Tukey, P=0.05). Eriophyoid mites present in open surfaces (vagrants) were identified but excluded from the population analses Acalitus essigi andA. orthomerus were found in nine morphological structures of the plants, showing preferences for vegetative buds, reproductive buds, and polydrupes, where both species were frequently found in coexistence. Redberry occurred in the late stages of polydrupe harvest in Tupy and X001 varieties, while the SP-Erandy variety did not show symptoms of this disease. The coexistence ofA. essigi andA. orthomerus as mites associated with red berry disease suggests a complex relationship in their contribution to this disease, and that they could be a single species, with dimorphism characteristic of deuterogyny.Acalitus essigi has its lowest population during the formation of flower buds, then presents two population peaks during the stimulation stage, and recolonizes at the final stage of harvest. In contrast, A. orthomerus persists in vegetative buds throughout all phenological stages. The varieties studied show different susceptibility to red berries, while Tupy and X001 showed symptoms of the disease, SP-Erandy did not show any damage. Two vagrant species were identified as Diptacus rubuscolum and Aculus schlechtendali.