Shot hole disease (Coryneum blight)—Wilsonomyces
carpophilus
Shot hole, or Coryneum blight, is a serious disease of almonds, apricots, nectarines, peaches, and other Prunus species in
California. Reddish or purplish
brown spots about 0.10 inch in diameter occur on new leaves and shoots. The spots expand and their centers
turn brown. Tiny, dark specks sometimes form in the center of lesions, especially on leaves. Spots on
young leaves have a narrow, light green or yellow margin and their centers often fall out as leaves expand,
leaving "shot holes." Buds of peach, nectarine, and sometimes apricot are killed in the winter.
Fruit may become rough and corky. Spotting occurs on the upper surface. Concentric lesions may develop
on branches.
Life cycle
Solutions
Prune and dispose of infected tissue as soon as it appears. After leaf drop, inspect plants carefully and prune infected buds and twigs with lesions. Diligent sanitation and water
management can provide adequate control where the incidence
of shot hole is low. Avoid overhead sprinklers or use a
low angle to avoid wetting foliage. Also, some varieties
may be less susceptible. Where disease incidence is high,
fungicides such as Bordeaux
mixtures or fixed
coppers may be applied. On peaches and nectarines, a dormant
spray of copper in late fall will work well. On almonds,
spray fungicides at petal fall in the spring. |
Shot
hole on young apricots |
Shot
hole damage from left to right on peach, almond, apricot,
and cherry |
Infected
twig |
Shot
holes |
|
