Serviceberry, Shadbush or Saskatoon Berry - a member of Rose family

Damage looks like rust and poor water management

Four years ago we planted four serviceberry plants in hopes that they would serve as a barrier between two sections of the garden. We have not seen any significant growth nor have we gotten any berries.  This year their leaves are turning yellow long before fall.  They are also getting rust. 

Poor water management, poor drainage

Inappropriate watering commonly damages landscape plants. Inadequate water causes foliage to wilt, discolor, and drop. Prolonged moisture and poor drainage results in smaller leaves, dieback or limb drop, and susceptibility to root rots, mineral deficiencies or toxicities, wood-boring insects and other pests that eventually can kill plants. Excessive moisture smothers and kills roots. As roots die, discolored and dying foliage appears in the above ground portion of the plant.

Maintain adequate but not excessive water in the soil to ensure plant survival and good growth. Examine plants regularly for symptoms of water stress. Monitor soil moisture around the plant's root zone and adjust irrigation according to seasonal need. Soil around young plants during hot weather may need to be monitored daily; every few weeks may be adequate when monitoring around mature trees during more favorable weather.

Do not water established trees and shrubs near the trunk; this promotes root and crown disease. Water plants when needed around the drip line and beyond. Adjust sprinklers or install deflectors to prevent wetting of trunks. Move drip emitters away from the base of the trunk after plants are established. Read more at the UC Davis website here.

Serviceberry plant

Rusts

Rusts are fungal diseases that infect many hosts, including birch, cottonwood, cypress, false cypress, fuchsia, hawthorn, juniper, pine, poplar, rhododendron, rose, and spruce. Dry reddish, yellowish, or orange spore masses or pustules form on infected tissue, especially on the lower surface of leaves. The upper surface of heavily infested leaves turns yellow or brown and infected leaves may drop prematurely. Orange, gelatinous masses appear on some infected evergreen hosts. Some species cause tissue swellings or galls, colorful spots on plants, or cankers on bark. These can cause branch dieback and occasionally kill the entire plant. Some rusts may cause leaves and shoots to become distorted, dwarfed, and discolored, forming "witches' brooms."

Avoid overhead watering, which favors spore germination. Rake infected leaves or needles and clip and dispose of infected shoots and branches as soon as they appear. Fungicides applied in the spring can reduce some rust diseases, but the frequent applications required to provide good control are generally not warranted in landscapes. Read more from UC Davis website.

Leaf spot may also be present 
Entomosporium leaf spot is a fungal disease that spots the leaves of plants in the Pomoideae group of the rose family, including apple, flowering crab apple, evergreen pear, hawthorn, pear, photinia, pyracantha, quince, Rhaphiolepis, and toyon. And in this case serviceberries. Tiny reddish spots, sometimes surrounded by a yellow halo, appear on the leaves of infected plants, usually on older growth. These spots darken and enlarge as the leaves mature. Spore-forming bodies eventually appear in the center of the spots; these dark fruiting bodies may appear to be covered with a glossy membrane, beneath which white masses of spores may be visible. Infected plants may prematurely drop many leaves.

Remove and dispose of spotted leaves that are on plants or have fallen. Do not water overhead as this spreads the fungus spores and favors infection. Reduce humidity around plants by providing adequate space between them and by pruning lower branches. Consider removing groundcovers beneath shrubs and mulching or maintaining bare soil instead. In very severe or special cases, copper compounds or chlorothalonil may be used as a preventative treatment. Read more here.

About serviceberries

Serviceberries are deciduous shrubs or small trees.  New leaves in spring are purplish and turn dark green in the summer.  Leaves become yellow, orange, or red in the fall.  Clusters of white or pink flowers bloom in spring followed by production of small berries that attract birds.  Berries are often used in pies and jams. 

Serviceberries do best in areas with full sun or partial shade.  Plant in a site where fruit drop won’t be a problem.  Provide moderate to regular amounts of water.  Prune after bloom to remove old, damaged, or crossing branches. Read more here.