Scab—Spilocaea and Venturia spp.
Fungal scabs affect many hosts. Spilocaea spp. commonly infect apple, pear, pyracantha, and toyon.
Venturia spp. infect coffeeberry, cotoneaster, cypress, poplar, and willow. Olive green to black,
circular, scabby or velvety spots appear on infected leaves, which may yellow or redden and drop prematurely.
Scabby spots, often more sunken, may appear on fruit, which may crack or shrivel and drop. Shoots may
die back if the disease is severe.
Identification of species | Life
cycle
Solutions
Remove and dispose of fallen leaves in the
fall. Fall foliar fertilizer (urea) applications on deciduous
hosts hasten leaf drop and promote leaf decomposition, reducing
the number of spores in spring. Avoid
overhead sprinkling, which splashes spores onto the plant,
or irrigate early in the day so that foliage dries more
quickly. Sulfur, Bordeaux
mixture, or narrow
range oils applied
about weekly to foliage during wet weather before disease
develops
can prevent the disease, but chemical control is generally
not warranted, and is impractical on large trees, except
where the disease is severe
on apple or pear fruit. Vigorous plants tolerate extensive
leaf scabbing, so provide plants with proper cultural care.
For apple scab, see the Apple
Scab Pest Note. | 
Scab
lesions on toyon leaves
Scabby spots on apples
|
