yields of quality strawberries require vigorous growth and healthy
plants. Growth can be affected by many different factors such as
soil fertility, lack of moisture, weeds, insects, and
can control all of these factors, while certain factors, such as
weather conditions, cannot be controlled. Growers can also control
plant growth characteristics, productivities, and blossom
hardiness by selecting different varieties.
sound strawberry production program should include the control of
all pests and the use of good cultural practices. A total program
replaces most of the “luck factor” and results in excellent
crop production yearly.
strawberries when the berry is fully ripe. The first harvest can occur
approximately 30 days after first bloom. Check the planting every other
day for ripe fruit. White areas on the berry indicate immaturity. Allowing
the berry to reach full color on the plant increases the sugar content and
the size of the berry. Pick the berries with the stem and cap attached to
allow the fruit to keep for a longer period. Berries that have their caps
removed or are injured become inedible, and also lose their vitamin C
content within 48 to 72 hours.
pick without bruising, slip your index and second fingers behind a berry
with its stem between your fingers, twist the stem a bit and pull with a
sharp jerk. The stem will snap off about 1/2 inch from the berry
(see diagram on left).
berries are large and thick-stemmed, cradle each one in your hand and
pinch off the stem between your thumbnail and index finger (see diagram on
- Pick only the berries that are fully
red. Part the leaves with your hands to look for hidden berries ready
- Pick the row clean. Remove from the
plants berries showing rot, sunburn, insect or bird injury, or other
defects and dispose of them, or keep ones with good parts separate
from the healthy berries.
- Berries to be used immediately may be
picked any time, but if you plan to hold the fruit for a few days, try
to pick in the early morning or on cool, cloudy days. Berries picked
during the heat of the day become soft, are easily bruised, and will
not keep well.
- Avoid placing the picked berries in the
sun any longer than necessary. It is better to put them in the shade
of a tree or shed.
- Cool them as soon as possible after
picking. Strawberries may be kept fresh in the refrigerator for 3 or
more days, depending upon the initial quality of the berry. After a
few days in storage, however, the fruit loses its bright color and
fresh flavor and tends to shrivel.
- Store in the refrigerator in shallow
containers, uncovered or lightly covered. Do not wash until
ready to use.
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are attacked by many pests and diseases that vary widely in their
destructiveness and distribution. Preventative disease control measures
begin with planting disease-free stock with genetic resistance and using
recommended cultural practices. The production of disease-free plants and
fruits may also require preventative applications of fungicides or
insecticides. When using these to control pests and diseases of foliage
and fruit, follow label directions and the time limit given for “last
application before harvest.”
are the pests and diseases that most often affect strawberries, and ways
to control them. For more information on dealing with and preventing
fungus and insect problems, check out the Fungus
Problems and Insect Problems pages.
feeding may be a problem in some plantings. Protective netting
is available from garden centers and must be put in place before the birds
begin feeding on the fruit. Prop the netting two inches above the foliage
and secure it around the edges to prevent the birds from being able to
reach the fruit.
Causes of malformed fruit
or "button berries"
(see at left) may be caused by feeding tarnished plant bugs (see below),
heavy infestations of cyclamen mites, frost injury, nutrient deficiencies
(boron, calcium), inadequate pollination, abnormally high temperatures
that make pollen nonviable, or by the application of 2,4-D from August 1
to November 1, when fruit buds are differentiating.
Fasciated berries, those that have a
cockscomb shape as if several berries have grown together with multiple
tips, are caused by short day-lengths in the fall or by cold, dry weather
during this time. Fasciated fruit often occurs when cultivars adapted to
northern conditions are grown in the south.
Crown and Fruit Rot
rot occurs when the fungus grows into crowns from infected
runners or petioles. Plants with crown rot may die in the nursery or
after being transferred to production fields. Wilting plants with
crown rot have a reddish brown, firm rot of the interior of the
crown. This can be seen most easily by cutting through the crown
length wise. Crown rot is sometimes difficult to identify on the
basis of crown discoloration because crowns of dying strawberry plants
turn brown regardless of what kills them.
rot can occur on both ripe and unripe fruit. Infected
tissue on ripening fruit appears as round, firm, sunken, tan to brown
spots that turn into sunken black lesions with age. Spots may remain
a light tan for a few days, especially during wet weather. The
entire fruit may become infected, dried, and mummified. Dark brown
to black, firm lesions can occur on green fruit of susceptible cultivars.
Sources of anthracnose are difficult to
determine. The fungus can survive for several months in soil or on
plant debris. Anthracnose may also survive on alternate hosts during
the summer. Infected transplant material can act as the primary
source of the disease. Anthracnose is favored by warm to hot, wet
conditions with high relative humidity.
Control of anthracnose begins by
transplanting disease-free material. Follow a protective fungicide
program from transplanting through harvest. Avoid overhead
irrigation if possible. If fruit rot occurs, remove all infected
fruit at each harvest. To prevent spread of the disease, pickers
should never move from an infected to a non-infected field.
Strawberry varieties resistant to anthracnose are currently being
Leaf symptoms appear as white
patches of mycelium on the lower leaf surface. The entire lower leaf
surface may be covered, the leaf edges roll upward, and purple to reddish
areas develop on the lower leaf surface. Losses result from infection of
flowers and fruits, while leaf infection has not significantly reduced
yields. A high degree of resistance is present in many cultivars.
spots. This complex of foliage problems includes: Leaf Scorch
(Red Spot), Leaf Spot, Purple Leaf Spot, and several other leaf diseases.
The symptoms are characterized by numerous irregular purple blotches,
round lesions with red rusty borders and white centers, or spreading
lesions that cover nearly the entire leaflet. Leaf diseases survive the
winter on infected leaves as conidia or other over wintering fungal
structures. The new disease cycle begins when rain or wind disperse fungal
material to new leaves. Mid-age leaves are most susceptible and protective
fungicides are required when susceptible cultivars are grown. Resistant
cultivars of pathogen-free stock are desired.
Slime molds. Slime mold fungi may be
found on strawberry plants and mulch during the warm, wet weather of
spring or fall. This creamy white or tan colored, jellylike mass moves out
of the soil and up onto leaves and grasses. It produces variously shaped
and colored, crusty structures with powdery dry spores. Slime molds are
found on fruit grown under plastic. These fungi are not parasitic to
plants but can smother single leaves or fruits and be unsightly. Slime
molds disappear when hot dry weather returns and do not require treatment.
Root and Crown Diseases
Red Stele. Diseased
plants occur in patches and produce fewer runners and smaller berries. The
tips of young roots rot first, after which the stele of infected roots
becomes red. Lateral roots also die and decay, producing a “rattail”
symptom. Red color may extend up to the plant crown. Plants may appear
stunted or wilted, and leaf color may change to red, orange, or yellow.
Avoid soil compaction and improve drainage. Plant resistant cultivars from
inspected planting stock.
Wilt. Damage from this disease is often most severe in the
first year of growth. The oldest leaves show marginal and interveinal
(between the veins) browning and death, while newer leaves are stunted but
remain green and don’t wilt. The symptom often appears in late spring
with the onset of hot temperatures and dry periods, or with stress from
high light intensity. Planting disease-free stock in soil without a
history of Verticillium has been successful. However, this fungus has
become widespread, so use of disease-resistant varieties and soil
fumigation may be needed.
Black Root Rot. This is caused by a
complex of root-attacking fungi, injurious environmental conditions
(freezing or water logging of soil), nematodes, or any combination of
these factors. Infected roots turn dark and lose their feeder roots. Black
root rot causes poor plant vigor. This problem is associated with soils of
high clay content, excessive irrigation, and soil compaction. Avoid these
soils and provide adequate soil aeration for vigorous root growth.
Nematodes. Parasitic nematodes are small
round worms that range in size from one-sixty-fourth to one-sixteenth of
an inch long. Some species of nematodes cause serious damage to
strawberries when they occur in high numbers. Root-knot nematodes cause
characteristic knots or galls on roots.
associated with root-knot and other nematodes: stunting,
yellowing of leaves, reduced berry yields, reduced production of runner
plants, wilting, and general loss of vigor. Severe infestations of
nematodes on strawberry plants have been found in a few instances in
Nematode root diseases are almost impossible to diagnose from symptoms
alone (see nematode leaf damage at left and a whole plant affected below
right). To make an accurate diagnosis, nematodes must be recovered and
identified from diseased plants and soil. Such a diagnosis can be made
only in a specially equipped laboratory by trained personnel.
The basic principle of nematode control in strawberries is planting only
nematode-free strawberry plants in nematode-free soil. Eliminating
nematodes from the soil is, at best, a rather expensive and difficult
task. The basic method of field-scale nematode control is soil fumigation
(application of chemicals). Crop rotation is generally more economical
than soil fumigation if land is available.
are found in the soil and are too small to be seen with the naked eye.
Most nematodes feed on roots. Symptoms of nematode damage include galls on
the roots or stubby, stunted roots. To avoid a buildup of nematodes,
rotate plantings to a different site when establishing new beds.
plant bugs cause deformed or
"nubbin" berries with a concentration of seeds at the tip of the
fruit. Nymphs puncture individual seeds and inject a toxin so that the
fleshy part of the berry stops developing where the seed was injured.
Damaged seeds are hollow and turn a straw-brown color. Plant bugs are
often in alfalfa; to prevent the bugs from feeding on strawberries, avoid
mowing alfalfa when strawberry plants are in bloom. Go to Insect Problems
for a listing of products that may be applied to control insect pests on
rollers are small worms that
roll the leaves together and feed on the leaves. They must be controlled
if they become numerous.
are tiny, spider-like creatures that are typically found on the
underside of leaves. Mites tend to be the most damaging during hot, dry
periods, when they suck plant juices from the leaves. There are two
main types of mites - the red spider mite and the two-spotted mite (shown
Strawberry weevils or clippers puncture
fruit buds with their snouts to feed on immature pollen. Later, females
deposit an egg inside a floral bud and girdle the petiole of the bud so
that it falls to the ground or is left hanging by a small bit of tissue.
Slugs eat holes in ripe fruit and are
worse during rainy weather or near rotting foliage. Shiny slime trails are
evidence of slugs.
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