COMMENTS on disease
is caused by the fungusDisculadestructiva. Dogwood anthracnose is most
severe only in areas of the state that are higher than 2000 feet. A few cases
have been reported at lower elevations where dogwoods are grown in very cool,
moist, shady locations. It is a serious disease capable of killing large
numbers of trees and most Cornus species can become infected.
first symptoms that appear in the spring are spots on the leaves and flower
bracts. Leaf symptoms develop first in the lower canopy and progress up the
tree. Infected leaves have tan spots with purple edges, dry brown margins or
large blotches on them. Blighted gray or drooping leaves hang on the twigs and
are often the first symptoms noticed during cool, wet weather.
spreads into the shoots, main branches, and trunk causing brown sunken areas
(cankers) to occur. Cankers can girdle and kill individual branches or twigs.
Multiple cankers can girdle the main trunk and eventually kill the tree.
Diseased trees produce numerous epicormic shoots or "water sprouts"
on the lower trunk and lower limbs, which soon become infecte.
resistant species and cultivars is an excellent option for managing this
disease in the landscape. Kousa dogwood (Cornuskousa) is generally
resistant to dogwood anthracnose and is a better choice for replanting in sites
where dogwoods have died from this disease. Crosses between Cornuskousaand Cornusflorida (Rutger`s
Hybrids) have greater disease resistance to dogwood anthracnose and include: `Aurora`,
`Celestial`, `Galaxy`, `Ruth Ellen`, `Star Dust`, `Stellar Pink` and `Constellation`. Cornusflorida `Appalachian
Spring` has a high level of resistance to anthracnose.
combination of cultural and chemical measures is necessary to control this
disease. Effective control may be possible if the disease is detected before
branch dieback begins.
hot, dry summer weather, prune and dispose of all dead or cankered twigs and
limbs. Remove all "water sprouts." Rake and remove fallen leaves. Do
not leave dead leaves attached to the tree. Improve air circulation and light
penetration by removing understory plants and crowding vegetation.
high applications of nitrogen fertilizer, since this can promote very succulent
(susceptible) new shoots. Maintain healthy dogwoods by following recommended
transplanting dogwood seedlings from the woods as these plants may harbor the
fungus. Fungicide sprays to protect the new
leaves and shoots need to begin at bud break in early spring. Fungicides for
spot anthracnose will also help to control dogwood anthracnose. These include:
chlorothalonil, mancozeb, propiconazole, thiophanate-methyl or copper