AGRICULTURAL RESEARCH AND EDUCATION CENTER
IFAS, UNIVERSITY OF FLORIDA i
13138 LEWIS GALLAGHER ROAD
DOVER, FL 33527 c L
Dover AREC Res arch Report DOV-1991-4 March, 1991
MISSHAPEN STRAWBERRY FRUIT
E. Albregts, C. M. Howard, and C. K. Chandler1
About 5,000 ac es of strawberry are grown in Florida and most of the
acreage is loc ted around Plant City, with the remainder scattered about
the state. very season a problem with fruit quality, especially
misshapen frui arises. Often the cause of the misshapen fruit is not
evident by the time it is noticed. There are many causes of misshapen
fruit and some of the more important ones are discussed in the following
The size and sh pe of a strawberry fruit is a function of the number of
ovules fertili ed. The ovules develop into achenes (seeds) which
produce growth regulators that control the growth of the fruit.
Mechanical or d sease injury to the flower, failure of the flower to be
adequately pollinated, or injury or destruction of seeds may result in
cessation of gr wth of some or all of the fleshy portion of the fruit.
The fruit will e misshapen to the extent of the loss of viable seeds.
Factors which a fect the viability of the seeds on strawberry fruit are
many and most o these are listed in the following.
A boron deficie cy may cause misshapen fruit and, in addition, reduce
fruit number and yield. Boron deficient plants have the usual distorted
young leaves wit tip burn, and flowers which are generally smaller than
normal. Fruit ma be small with bumps of growth where a viable seed or
seeds have survived. Adequate levels of available boron should be
maintained in th soil since boron leaches readily from Florida's sandy
soils. Most of the boron in the soil is associated with the organic
matter. To help maintain boron in the soil, the organic matter content
should be main ained or increased with planting of cover crops,
application of anure, and incorporation of crop residues. Organic
matter in sandy oils also adds tilth and reduces leaching of soluble
nutrients. When the leaf boron content is less then 23 to 25 ppm,
sufficient boron should be applied to the foliage to correct a potential
problem (about 1 3 Ib/acre of actual boron). In addition, excessive
nitrogen applied o the soil as well as nutrient imbalances have also
been shown to cau e misshapen fruit. Low levels of copper and zinc may
Professor (Soil scientist Professor (Plant Pathologist), and Assist.
Professor (Plant Breeder), respectively.
also cause misshapen fruit.
Freezing weather may result in damaged or dead flowers and fruit.
Normally flowers on Florida plants will be damaged or killed when the
temperature of the flower surface is about 300F. A period of very warm
weather followed by a freeze may raise the freeze damage threshold
temperature of flowers to near freezing, and conversely, a period of
cold weather can lower the threshold. Resistance to fruit and plant
freeze damage also varies somewhat with the cultivar. The northern
developed cultivars are more freeze tolerant than southern developed
cultivars. Freeze damage on fruit is expressed by seediness in the area
affected and is generally on the tip portion of the fruit. Freeze
damage may also occur at other places on the fruit which are exposed to
the weather. Normally the area affected changes color and dehydrates
resulting in a brown to black area, usually seedy. If a flower is
killed, it will be brown at first and will then turn black very rapidly.
If the flower is only damaged, the area affected is usually the tip. As
the fruit enlarges, the damaged portion remains as a sunken area
surrounded by normal tissue. Seediness is generally not observed with
freeze damage to flowers since seeds have not developed. At times the
larger fruit may split when some of the seeds do not develop on the tip
of the fruit. To prevent or reduce freeze damage, one needs to protect
the flowers and fruit with freeze control measures, such as overhead
sprinkler irrigation and/or row covers.
The application of pesticides to plants may, under some circumstances,
adversely affect the plant, flower, and fruit. It has been shown that
captain applied at a high concentration during pollination can cause
misshapen fruit. Captan appears to prevent pollen germination, and
exposed flowers are more likely to be affected than those under the
foliage. As expected, some cultivars are more susceptible than others
to flower damage from captain. Since Florida strawberry plants flower
for most of the fruiting season, and the susceptibility to captain damage
of the cultivar in use is not known, the best defense when using captain
as a fungicide is to follow the manufacturer's recommendation as to rate
and concentration of application.
The herbicide 2,4-0 will not only cause distortion or death of the
strawberry plant, but may cause misshapen fruit at very low
concentrations. The fruit are usually disk shaped or convoluted.
Atrazine even at very low levels may also cause flowers to die or fruit
to be misshapen. Other pesticides may also cause misshapen fruit or
surface damage. The spraying of some insecticides can affect the
pollinating insect population. Lack of insect pollinators generally
results in lower yields and more misshapen fruit. Flowers under heavy
foliage and/or in dense planting may have poor pollination because of
the lack of insects or wind or both.
We all know t at insects can be beneficial, such as bees, or detrimental
as noted here One detrimental insect is the tarnished plant bug which
generally att cks the tip of the strawberry flower and damages or kills
the seed. P orly developed or hollow seeds then concentrate at the
apical end f the fruit giving a very seedy and usually a flat
appearance. pittlebugs, mites, and thrips also have been reported to
cause misshap n fruit.
Disease organisms may also cause misshapen fruit. A Rhizoctonia species
can cause anth r and pistil blight which may result in malformed fruit.
A fungus from the family Moniliaceae may also cause misshapen fruit.
Severe infecti n with leaf spot and leaf scorch (leaf and calyx) can
cause misshape fruit or sterile flowers. Gray mold, (Botrytis) also
has been impli ated in causing misshapen fruit.
Pollination ma be poor during the short days of winter and/or under low
light intensity es, such as heavy clouds for several days, and during
cold wet weath r. Temperatures below 60 F may impair pollen growth and
germination an result in misshapen fruit with some cultivars. The
first flowers o open with some cultivars have low amounts of pollen
and/or poor qua ity pollen which may result in insufficient pollination
and misshapen f uit. Cultivars vary greatly in the amount of and in the
quality of the ollen. Some consistently produce large amounts of high
quality pollen, while others always produce low levels of poor quality
pollen, and oth rs somewhere in between. The quality of pollen that
some cultivars produce is weather related. For example, certain
cultivars produ e poor quality pollen when temperatures are below normal
for the cultiva
Insects such as lies, thrips, wasps, beetles, butterflies, and various
bees visit stra berry flowers in the field. Bees appear to be the
insect which doe most of the pollination of strawberry flowers without
damaging them. Honey bees are not greatly attracted to strawberries,
thus large number s should be available to obtain good pollination. Bees
also appear to ave a cultivar preference and are most likely to be
involved with po lination during good weather. Research has stressed
the importance f bees in pollination of strawberry, and growers may
need to provide olonies of honey bees for pollination, especially for
larger fields. f course, growers should apply pesticides detrimental
to bees only whe needed and at the time of the day which will have the
least effect on t eir well being. This is usually in the late evening
or at night.
With susceptible cultivars, fasciation of the fruit can be a problem
during some seasons. Fasciation is a fruit malformation which varies
from a slightly flattened stem of the primary fruit with no fruit
development to a widely flattened stem with a cockscomb shape of the
fruit. Fasciation is a weather related problem and is most likely the
result of warmer than normal weather during the shortest days of the
year. Tissue cultured plants may also express this trait. Adverse
weather conditions during flower bud development may result in multiple
tipped fruit with some cultivars. In the north, this has occurred with
dry soil conditions and cold weather during flower bud formation.
Strawberry fruit shape is important, and many factors are involved. The
cultivar, weather, time of flowering, flower position on the plant,
insects, soil fertility, disease, pesticides, plant size and density,
light intensity, pollen quality and quantity, boron deficiency, nutrient
imbalances, and perhaps other factors have an influence on the shape,
quality and quantity of strawberry fruit. Some factors may influence
only the shape while others, such as pollen quality and quantity, can
affect fruit shape, average fruit weight, and total yield. A cultivar
may produce high yields of good quality fruit in one growing region,
while in another season or growing area, weather conditions may be
slightly different and fruit quality and quantity may both be deficient.
Quite often it is not possible to identify the cause of misshapen fruit.
By the time misshapen fruit are noticed, the causal agent may no longer
be present, and the symptoms on the fruit may not be indicative of the
Often more than one cultivar is planted in a field and only one will
display misshapen fruit. For the various factors causing misshapen
fruit, some cultivars are more susceptible than others to producing
misshapen fruit from a specific cause. This is especially true for
cultivars not adapted to the area or ones that grow well but were
developed in another climatic region.
Growers can reduce the risk of producing misshapen fruit if they (a)
provide the required plant nutrients in a balanced fertility program,
(b) use cultivars which are adapted to the area and are known to produce
good quality fruit, (c) provide sufficient insect pollinators and apply
pesticides only when needed and at the time of day least likely to
affect pollinators, (d) keep damaging insects under control by
monitoring fields and take appropriate action to bring them under
control when needed, (e) use good production practices that prevent
excessive plant growth, and use a plant spacing which does not crowd the
plants, (f) and follow label instructions when applying all pesticides.
1. Darrow, G. M. 1966. The Strawberry. Holt, Rinehart, and Winston,
2. Garren R. 1981. Causes of misshapen berries. Page 326-328. In The
Strawberry. N.F.Childers, ed. Horticultural Publications,
3. Kronenberg H. G., J. P. Braak, and A. E. Zeilinga. 1959. Poor
fruit sett ngs on strawberries, II. Malformed fruits in Jucunda.
4. Maas, J. L Editor 1984. Compendium of Strawberry Diseases. The
American P ytopathological Society, 3340 Pilot Knob Road, St. Paul,
5. McGregar, E. 1976. Insect pollination of cultivated plants.
Agricultur 1 Handbook No. 496. ARS-USDA
6. Parker, B. L. and R. P. Marini. 1978. Strawberry deformities.
Univ. Vt. gr. Expt. Sta. Bul. 683. 13 pp.
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
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site maintained by the Florida
Cooperative Extension Service.
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