In the springtime, toothpaste-like spores erupt from these galls. Each mass is called a teliohorn. Spores from teliohorns are blown to an alternate host where they cause leaf spot. These spots are small, bright orange-yellow, and surrounded by a red halo. Spores are produced on the underside of each leaf spot in hair-like projections.
Wind carries the disease back to junipers.
Spores produced on a juniper only infect the alternate host, and spores produced on the alternate host only infect a juniper. Although the galls are innocuous to the juniper, repeated infection on the alternate host can cause early defoliation, and smaller fruit. Defoliated trees may suffer winter injury and often fail to grow fruit the following season. Cultural controls include removing juniper galls before they produce spores and separating junipers from potential alternate hosts. A few hundred yards separation is generally sufficient for practical Garden purposes.