Control Plant Diseases
in yard and garden
Mimeo BP 4-1

Raspberry Anthracnose

Anthracnose is the most common and
widespread disease of raspberries, especial-
ly black raspberries. It attacks canes,
leaves and the stems of berry clusters,
stunting or destroying the planting and re-
ducing both fruit yield and quality.

Anthracnose also attacks blackberry,
western dewberry, cloudberry, European
bramble and loganberry.

SYMPTOMS

Anthracnose first appears in the spring
when the young raspberry canes are about 6
inches high. Small, purple, slightly-raised
spots are found scattered over the length of
the canes. These lesions soon enlarge, be-
come sunken in the center and turn gray with
purple borders. They eventually grow to
about 1/8 inch in diameter and run together
to form extensively diseased areas on
mature canes.

Then around mid-July, the leaves,
leaf veins, leaf stems and berry cluster
stems also become infected with small,
yellowish-white spots. Lesions on the stems
of fruit clusters will cause the clusters to
break off while the fruit is still hard and
green. Anthracnose sometimes causes the
brown, dried-up areas on ripe berries.

A severe outbreak of anthracnose will
stunt or destroy new canes. And infected
canes tend to crack during winter, causing
them to dry out and break in the fruiting
season. These canes are also more suscep-
tible to winter injury.

CAUSE

Anthracnose is caused by the fungus
Plectodiscella veneta, which overwinters in
lesions on old fruiting canes. Just as the
raspberry buds start to open in the spring,
the fungus produces spores that are carried
by wind and splashing rain to healthy, young
canes. The lesions that develop on these
"spring" canes then produce summer spores
that, in turn, spread the disease to leaves,
fruit, fruit stems and fruiting canes.

Young, tender canes are highly suscep-
tible to anthracnose infection during wet,
rainy periods. During dry weather, these
canes harden-off and resist the disease.

CONTROL

Unless you take the necessary steps for
controlling anthracnose, your raspberry
patch will be shortlived and unproductive.
Here are the steps of an effective control
program.

1.	Select a planting site that has good
air drainage to promote quick evaporation
of rains and dew on raspberry canes. Moist
conditions favor anthracnose infections.

2.	Plant only disease-free canes when
establishing a new patch, and remove
"handles" or old cane stubs before planting.

3.	Keep weeds cultivated from between
the rows in May and June. They not only
hold moisture but also interfere with proper
spray coverage.

Cooperative Extension Service PURDUE UNIVERSITY Lafayette, Indiana
Department of Botany and Plant Pathology, Life Science Building