As summer progresses, the aecia (infected needles) will begin to turn brown. The aecial host is the alternate host (look for pycnia and aecia). The aecia (specialized reproductive structures) are cup-shaped and have a conspicuous peridium. On the lower leaf surface, 20-30 cup-shaped aecia of the fungus form on each gall. This fertilization allows for aecia to form and in turn produce aeciospores. Mature lesions will then produce small tubes (aecia). The corresponding stage on the pear trees is known as aecia. The lesions turn orange in color and are now called aecia. Aecia sink in towards the center as they mature. Orange-brown pustules with a pale halo on leaves and stems replaces the aecia. These are actually aecia containing aeciospores for dispersal, making the broom a sign of disease. Aecia may also be referred to as "cluster cups". In midsummer, aecia appear on the epidermis of spruce needles as orange pustules.