Leading Producers of Strawberries

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Leading Producers of Strawberries

• State Harvested Acres
• California 25,000
• Oregon 6,200
• Florida 5,100
• New York 3,800
• North Carolina 2,400
• Pennsylvania 1,500
• Washington 1,500
• LOUISIANA 1,100 1st in taste
• USDA 1995

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Morphology
a, crown and leaf bases b, stolon (runner) c,
first (blind) runner node d, daughter plant
e, secondary runner
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Production Strategies

• Matted Row System
• Consists of rows 12 to 24 inches wide that are
  allowed to fill in or be renewed with runner
  plants.
• Fields are renewed or renovated each year. Fields
  planted in the matted row system generally
  produce three to four profitable crops. If
  disease, insects, or weeds heavily infest a
  planting, renovation may not be economically
  justified.
• Annual Hill Plasticulture
• The annual hill system is a high-density system
  that grows strawberries as annuals. This system
  consists of closely spaced plants in double rows
  planted on raised beds covered with black
  plastic. Plasticulture is an annual system of
  planting freshly plants in the fall. Plants and
  plastic are removed after spring harvest and the
  process begins again the next fall.

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Important Diseases

• Red Stele
• Anthracnose and Black Leaf Spot
• Botrytis Grey Mold
• Mycosphaerella Leaf Spot
• Many viruses, insects and regional nematodes and
  numerous abiotic constraints that will not be
  covered

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Red Stele

• Pathogen Phytophthora fragariae
• Distribution Serious disease of strawberry in
  the northern 2/3 of the United States.
• Many desirable commercial cultivars are highly
  susceptible.
• Thrives in poorly drained, cool, wet soils.

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Symptoms

• Aboveground Symptoms of red stele rarely occur
  in the first year of strawberry growth unless
  plants are infected before planting or if
  conditions are suitable for rapid fungal growth.
• The disease is first noticed during bloom of the
  second year. The symptoms will be most noticeable
  in low or soil compacted areas of a field where
  water drainage is poor.
• Strawberry plants will show a general lack of
  vigor with poor runner growth and small berries.
• New leaves may appear bluish-green, while older
  leaves sometimes turn red, orange or yellow. The
  leaves tend to wilt during warm weather or
  drought stress.
• Severely diseased plants may collapse prior to
  fruiting.
• Although these aboveground symptoms are typical
  for red stele, they may resemble symptoms caused
  by other types of root disorders therefore,
  roots also need to be examined.

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Symptoms
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Symptoms

• Belowground To correctly diagnose, roots should
  be sampled during early spring and summer up
  until harvest.
• Samples taken after harvest are not reliable
  because infected roots may have already begun to
  decay.
• If red stele is present, the roots will appear
  unbranched and will be lacking feeder roots. This
  "rat-tail" appearance of the root is a diagnostic
  trait of red stele.
• Infected roots will have a reddish-brown core,
  but the outer tissue will be white. The
  discoloration will begin at the root tip and move
  upwards, but usually will not move into the
  crown.
• This is in contrast to another root disease,
  black root rot, in which outer root tissues are
  affected earlier than the inner (stele) root
  area. Normal roots have both a white center and
  outer root surface

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Symptoms
Red Stele, Rat tail appearance
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Disease Cycle

• The fungus is spread from one field, or area to
  another by the distribution of nursery infected
  plants. Infection is then spread within the field
  by moving water and by soil movement.
• Once in the field, oospores in roots produce
  zoospores when soil moisture is high, infecting
  the tips of the young, fleshy roots and
  destroying water- and food-conducting tissues.
• Infection and growth of the fungus in roots
  reduces the flow of water and nutrients to the
  developing leaves and fruit causing drought-like
  symptoms in the plant.

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Disease Cycle

• The optimum temp. for growth and infection is 57
  F. When soil moisture is high and the temperature
  is cool, plants show symptoms within 10 days
  after infection.
• The fungus is inactive at 40 F and above 86 F.
  The critical periods for development and spread
  are in the spring and the fall.
• As summer, soil temperatures rise, the fungus
  forms oospores in the stele of infected roots.
  The fungus survives periods of hot, dry, or cold
  weather primarily as these oospores

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Disease Management Pre-Plant

• Soil drainage the pathogen requires free water
  in order to develop. Avoid low-lying areas, and,
  raised beds 10 inches or more.
• Can persist in the soil for at feast 17 years,
  even in the absence of strawberry plants no
  crop rotation benefits.
• Site Preparation Cover crops can build organic
  matter in the soil (heavy, compacted soils favor
  red stele).
• Sanitation Clean cultivators or equipment.
• Planting Exclusion and prevention. The pathogen
  is introduced most frequently on infected-plants
  therefore, mother plants should be purchased from
  a reputable nursery.
• Host Resistance Resistant varieties" are not
  resistant to all strains of P. fragariae

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Disease Management Post - Plant

• Use cultural practices which favor good plant
  growth and development.
• Avoid over irrigation.
• Chemical Soil fumigation with soil sterilants
  and/or pesticide applications may be helpful in
  situations where resistant varieties are not
  available or are not adapted.

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Anthracnose and Black Leaf Spot

• Pathogens Colletotrichum acutatum, C. fragariae,
  
• Distribution Throughout the United States
• The fungus may cause petiole and runner
  infections, flower blight, and anthracnose crown
  rot.
• Flowers and ripening fruit are very susceptible
  to anthracnose fruit rot.

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Symptoms

• Lesions on stolons and petioles are sunken, firm,
  dark, and dry with a sharp line separating
  healthy from diseased tissue. When a runner is
  girdled by a lesion, the daughter plants beyond
  the lesion wilt and die. Lesions on petioles also
  result in the death of leaves.

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Symptoms

• Crown 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 in the interior of the crown.
• Crown rot is sometimes difficult to identify
  just on the basis of crown discoloration because
  crowns of dying strawberry plants turn brown
  regardless of what kills them.

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Symptoms and Signs

• Fruit 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.
• The spots may remain a light tan color 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
  the green fruit.
• Under humid conditions, salmon colored
  sporulation may be visible on the lesions.

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Progression of fruit lesion
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Symptoms

• Leaves Lesions on leaves are small (lt1/4"),
  round, and black (sometimes light gray) often
  resembling ink spots.
• Spots may become numerous on leaflets without
  causing leaf death and often appear first on
  expanding leaves of runner plants.
• The presence of leaf spot may be a warning signal
  that abundant inoculum is present on other plant
  parts and fungicide applications are needed.

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Disease Development

• Infected transplants and soil from infected
  transplants appear to be the primary source of
  inoculum in most instances, especially in annual
  production systems.
• This may be especially true for C. fragariae,
  which has a limited host range and does not
  survive in soil over the summer.
• In perennial systems, the fungi may overseason
  in infected plants and debris, providing inoculum
  for the following fruiting season.
• Conidia may be dispersed in the field by
  wind-driven rain, splashing water, insects,
  movement of workers, equipment or animals.

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Disease Development

• Disease development and spread is minimal in most
  cases under cool, dry conditions.
• Crown infections often occur in the nursery but
  do not appear until after planting.
• The fungus continues to develop in newly planted
  nursery infected plants, which may suddenly die
  during warm weather in the fall or early spring
  of the following year.
• Infected berries eventually dry up and mummify
  and can become a source of inoculum for the
  following season.
• C. acutatum is known to survive in infected plant
  material for up to nine months

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Management

• Difficult to control when conditions are
  favorable for infection during harvest. Control
  measures must begin early in the season.
• Disease-free planting material, however it is
  difficult to detect the fungus in planting
  material because it causes latent infections.
• 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 the spread of the disease, never move
  pickers from an infected to a non-infested field.
  
• When they are available, plant strawberry
  varieties resistant to anthracnose (Resistant
  varieties are currently being developed).

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Botrytis Grey Mold

• One of the most common and serious diseases, in
  wet seasons on unsprayed plants 80-90 losses of
  flowers and fruit can occur
• Causal agent Botrytis cinerea

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Symptoms and Signs

• Young blossoms are very susceptible to
  infections. One or several blossoms in a cluster
  may show blasting.
• Soft, light brown lesion form at calyx end of
  fruit with lesions without distinct borders
• Produces light grey spores that are easily
  airborne.
• Berries resting on soil or touching other
  decaying fruit often infected
• Good berries become a rotted mass within 48 hours
• Berries soon dry out leaving dark brown, mummies
  covered with grey-white fungal growth.

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Single or in Clusters
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Stages of symptomsEarly Mummy
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Disease Cycle

• Fungus overwinters as minute, irregular, black
  fungal bodies (sclerotia) and as dormant mycelium
  on dead leaves, stems, fruit and on annual weeds.
• In spring, sclerotia produces conidia, wind,
  splashing water, human activity spread throughout
  the patch depositing on blossoms, stems young
  fruit and leaves.
• Some plant parts may be infected in 3 hours.
  Temp 70-80, free moisture (rain, dew, fog,
  irrigation) are ideal for germination and
  infection.
• Fungus can penetrate unbroken skin of fruit.
• Single berry may contaminate many others in field
  or after harvesting.

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Factors Favoring Disease

• Moderate temperatures and long wetting periods or
  periods of humidity during bloom.
• Prolonged rainy and cloudy periods just before
  and during harvest.
• Dense foliage and wide rows keep plant wet
  longer, all varieties are susceptible but some
  are much more than others.

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Disease Management

• Avoid narrow rows
• Encourage air flow
• Apply fungicides
• Mulching with clean straw
• Black polyethylene sheeting
• Limiting cultivation from early bloom until after
  harvest
• Avoid wounding plants
• Care in handling berries
• Refrigeration of berries

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Mycosphaerella Leaf Spot

• One of the most common and widespread diseases of
  strawberry.
• Mycosphaerella fragariae is also the cause of
  black seed disease of strawberry fruit, which
  occurs occasionally in North America where
  Mycosphaerella leaf spot is present.
• Prior to the development of resistant cultivars
  and improved control programs, leaf spot was the
  most economically important strawberry disease.

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Symptoms

• Leaves Leaf symptoms vary with strawberry
  cultivar, strain of the fungus, and environmental
  conditions.
• Leaf lesions or "spots" are small and round (3-8
  mm diameter), dark purple to reddish, and are
  found on the upper leaf surfaces. The center of
  the spots becomes tan to gray to almost white,
  while the broad margins remain dark purple.
• Lesion centers on younger leaves stay light
  brown, with a definite reddish purple to rusty
  brown margin.
• Numerous spots may coalesce and cause death of
  the leaf.
• In warm humid weather, atypical solid rusty brown
  lesions without purple borders or light colored
  centers may form on young leaves. Lesions are
  evident on the undersurface of the leaf but are
  less intense in color, appearing as indistinct
  tan or bluish areas.

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Symptoms

• Leaf stems (petioles), runners, fruit stalks
  (pedicels), berry caps (calyxes) Almost
  identical to those on leaves. pathogen.
• Fruit Superficial black spots (6 mm in diameter)
  form on ripe berries under moist conditions.
  These spots surround groups of seeds (achenes) on
  the fruit surface. The surrounding tissue becomes
  brownish black, hard and leathery, however, no
  general decay of the infected berry occurs.
• Usually only 1-2 spots occur on a berry but some
  may have as many as 8-10 "black-seed". Symptoms
  are most conspicuous on white, unripe fruit and
  on ripe fruit of light colored cultivars.
• Economic losses in this case are due to
  unattractiveness of "black seed" spots on fruit,
  rather than fruit rot.

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Signs of the pathogen

• Late in the season, dark specks (sclerotia and/or
  perithecia) may be seen in older lesions.

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Disease Cycle - North

• In northern growing regions, the life cycle is
  somewhat different.
• Three sources of primary inoculum may be present
  conidia overwintering on living leaves, conidia
  from overwintering sclerotia, and ascospores.
• Abundant conidia, produced in early summer on
  lesions on both upper and lower leaf surfaces and
  lesions on other plant parts, are spread
  primarily by water splash.
• Sclerotia are produced during the winter on dead
  infected leaves. These may also produce abundant
  conidia in the spring.

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Disease Cycle - North

• Conidia also develop on occasion from the bases
  of perithecia. Perithecia are produced on upper
  surfaces of overwintered leaves. Forcibly
  discharged ascospores from these perithecia are
  wind disseminated.
• It is not known if these ascospores serve as an
  important source of primary inoculum, but they
  are most probably a means by which genetically
  different strains of the fungus may travel long
  distances.
• M. fragariae establishes in the stigma at the
  time of flowering and then grows to the achene.
  From there it infects surrounding berry
  (receptacle) tissue. Conidia produced in leaf
  infections are probably the primary inoculum
  source for fruit infections.

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Disease Cycle
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Disease Management

• Plant in well drained soil with good circulation
  and exposure.
• Choose disease resistant cultivars suitable for
  the region.
• Plant only disease free plants purchased from
  reliable nurseries.
• Apply nitrogen fertilizers only at renovation to
  reduce succulent new leaf tissue which is more
  susceptible.
• Remove older or infected leaves before setting
  runners in new plantings.
• Removing and burning all debris at renovation
  (after harvest) helps to reduce overwintering
  inoculum
• Fungicide spray schedule - Thoroughly cover all
  above ground plant parts with spray, especially
  undersides of leaves