Control Plant Disease
For Better Farming And Better Living
Mimeo BP 4-5
March 1956

STRAWBERRY HARVEST ROT

In years when cool wet weather prevails during strawberry pick-
ing time, or when heavy rains occur just before or during harvest,
losses from molds on ripe berries can be serious. Harvest rots of
strawberries are caused by common molds that live in the soil,and
they generally do not cause diseases that affect other parts of the
strawberry plant.

Gray_mold_fruit_rot is the most common and widely distributed
of the strawberry harvest rots. Gray mold rot is caused by the fun-
gus Botrytis sp. and will occur on both green and ripe fruits. It
generally starts on the part of the berry that is in contact with
the soil or on berries that touch other decayed fruits or dead leaves
It is first noticeable as a light brown, rather soft spot. In cool,
moist weather, the rot soon involves the entire fruit, which then
starts to dry out and becomes firm and tough and uniformly black in
coloro At this stage, infected fruits will be covered with a gray
powder or dusty appearing fungus growth — the well-known gray mold.
In some seasons, strawberry blossoms may become blighted by this
disease and petioles and flower stalks may be affected, resulting
in serious injury to the plant.

In cool wet seasons, it is not unusual for gray mold rot to
cause losses of 10 percent or more of the crop.

Leather rot_ may cause serious loss to berries at harvest time
and is readily distinguished from other fruit rots by the bitter
taste of affected berries. Berries in any stage of development,
either ripe or green, may be affected with leather rot. When green
berries are affected, all parts of the fruit become dark brown over
the affected areas. When affected berries are cut in half, the cen-
ter portion of the fruit will be light brown in color, which fades
into natural green or red at the margin of the fruit. Leather rot
is caused by the soilborne fungus Phytophthora cactorum and is usu-ally most troublesome when warm, rainy weather occurs at picking time
Rhizopus_Rot_or_Leak. Production of soft, collapsed, watery berries
is characteristic of the harvest rot referred to as fleakf. This
trouble is caused by the secondary molds, Aspergillus niger and
Rhizopus nigricans, that occur as common air contaminants, enter the
ripe berries through insect wounds, bird injuries or other types of
wounds, and quickly destroy the fruit within a day or two.
PURDUE UNIVERSITY Agricultural Extension Service, Lafayette, Indiana
Department of Botany and Plant Pathology, Life Science Building