Good Practices for Insect and Disease Control
Good Air/Water Drainage
Good air drainage and
circulation within the strawberry planting speeds the drying off of plants and
reduces the potential for infection. Botrytis (gray mold) requires wet foliage
or fruit for infection to take place. Similarly, it is important that the soil
dries out quickly after rain. Waterlogged soil increases the likelihood of
disease infection in the root system. Red stele and verticillium are two soil
fungi that can infect strawberry root systems more easily in wet soil.
No Shade
Plants need full
sunlight to grow and produce fruit, but sunlight also helps the foliage and
fruit to dry off quickly after a rain or heavy dew. Rapid drying will reduce
fruit and leaf diseases.
No Infested Runoff
Disease organisms (e.g., red stele,
verticillium, black root rot) can be carried in runoff water from a diseased
planting to a healthy planting. Do not plant new fruit plantings below older,
diseased plantings.
Rotation
Some crops can build disease organisms in the
soil, which can devastate the next crop if it is susceptible to the disease.
Strawberries should not follow tomatoes, potatoes, eggplant, peppers,
strawberries, raspberries or stone fruits for 5 years since these crops might
harbor the Verticillium fungus. Avoid an area with a history of
verticillium or red stele problems.
Resistant Varieties
Some plants are not
susceptible to certain diseases or are less susceptible than other varieties.
Resistance or tolerance to diseases will eliminate or greatly reduce the need
for disease control. Refer to Table 8.1 for
specific examples.
Disease-Free Planting Stock
Plant only disease-free
planting material. Since viruses cannot be seen at the time of planting, the
grower must rely on good propagation and cultural practice methods used by the
nursery in producing the plants. Virus-infected plants are infected for life,
and plants infected with soil-inhabiting fungi can contaminate the site for many
years. Buy only healthy plants from reputable nurseries.
Adequate Plant and Row Spacing
Most disease organisms
that cause foliage or fruit diseases require wet surface areas for infection to
take place. By speeding the drying time after rain or heavy dew, the grower can
greatly reduce the potential for disease development. Two important methods for
accomplishing this in a strawberry planting are to maintain narrow rows and a
low plant density within each row.
No Cultivation from Infested Soil
Cultivating in a
diseased planting and then moving that equipment to a healthy planting without
washing the soil from the equipment can transport disease organisms between
plantings.
Mulch to Prevent Winter Injury
Mulch will protect a
strawberry plant from winter injury. In some cases, strawberry plants may be
injured but not killed by cold temperatures. Those plants are often susceptible
to black root rot.
Avoid Frosted Blossoms
Strawberry flowers that have been
injured by frost are more susceptible to botrytis (gray mold). Avoid frost
injury to blossoms to reduce gray mold incidence in a planting.
Fungicide Sprays
Fungicide applications should be used
only if other control strategies are not adequate to control the disease.
Fungicide sprays will help in the control of powdery mildew and fruit rots.
Harvest before Overripe
The fruit rots will
spread more quickly on overripe fruit. Overripe fruit also will allow a disease
to build up in the planting, therefore making control more difficult.
Fruit Storage Conditions
Fruit rots will develop
more slowly or not at all if the fruit is cooled rapidly (to 40°F) after
picking.
Weed Control
Weeds can be a big problem in strawberry
beds. Hand weeding and using a generous layer of straw mulch are the best
options for control.
