Bladder galls are commonly observed on the leaves of Fragrant Sumac (Rhus aromatica), including in Colorado. What causes bladder galls on fragrant sumac?These galls are caused by the feeding activity of tiny eriophyid mites, specifically the Poison Ivy Leaf Gall Mite (Aculops rhois). These mites are too small to be seen with the naked eye and require at least 40x magnification to be observed. The mites inject chemicals into the plant tissue while feeding, which stimulates the abnormal growth of plant cells, resulting in the formation of galls. AppearanceBladder galls on Fragrant Sumac appear as irregular, wart-like, light green to reddish-green bumps on the upper surface of the leaflets. In heavy infestations, the leaves may become twisted and deformed. ImpactWhile these galls can be unsightly, they generally do not cause significant long-term harm to the overall health of the Fragrant Sumac plant. Heavy infestations may sometimes cause leaves to turn color and drop a bit early. ManagementIn most cases, control measures for bladder galls on fragrant sumac are not recommended or necessary due to their minimal impact on plant health. If the galls are bothering you aesthetically, you can physically remove them by trimming off the affected leaves, but avoid removing too much of the plant's growth, as the remaining parts still contribute to photosynthesis. Pesticides are generally not available or recommended for managing this specific pest, and their use may not be effective since the mites are protected inside the galls

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On Thu, 7 Aug, 2025 at 12:15 PM, Ask Extension wrote: