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Ministry of Agriculture, Food and Rural Affairs

Anthracnose

Anthracnose lesion on petiole Anthracnose lesion on fruit Anthracnose lesion on fruit Anthracnose sunken elliptical lesion on runner
Click to enlarge.

Beginner

Scientific Names
Colletotrichum fragariae, C. acutatum, C. gloeosporioides

Identification

  • Brown or black sunken lesions develop on green or ripe fruit.
  • Lesions remain round, sunken and fairly firm.
  • Salmon-coloured spore masses ooze from these lesions in humid conditions.
  • Distinct, dark, sunken lesions may form on petioles, runners and crowns.
  • Anthracnose infection may cause daughter plants to die, outer leaves to die prematurely or the plant may collapse from crown rot.

Often Confused With
Botrytis Grey Mould
Leather Rot
Verticillium wilt
Phytophthora crown rot

Period of Activity
Anthracnose outbreaks are very weather dependent. Infection is favoured by splashed rain and warm humid weather (20- 32°C or 68- 90°F, 100% RH), especially close to harvest.

Scouting Notes
Scout for disease when rain is followed by hot, humid conditions.  Watch for brown dried up bloom and brown lesions on fruit.  In late summer scout for runner lesions in both established and new plantings.  Plasticulture plantings are at higher risk.

Spore germination and infection requires 100% RH.  Warm to hot temperatures (20- 32°C or 68- 90°F) are optimum for disease development.

Thresholds

None established.  Treatment decisions are based on field history, and weather conditions.

Advanced

Scientific Names
Colletotrichum fragariae, C. acutatum, C. gloeosporioides

Several species of Colletotrichum can cause a range of symptoms on strawberries, collectively known as anthracnose.  The disease can attack fruit, blossoms, petioles, runners and crowns.

Identification
 Infections can occur on green or ripe fruit and present themselves as brown or black sunken circular lesions.  These lesions are distinct and fairly small (no larger than about 1.5 cm or 3/5 in. in diameter).  Salmon-coloured spore masses ooze from these lesions in humid conditions.

Distinct, dark, sunken lesions may form on petioles, runners and crowns. These lesions may cause daughter plants to die, outer leaves to die prematurely or the plant may collapse from crown rot.

Infected crowns, when cut lengthwise, are discoloured with reddish-brown streaks, creating a marbled effect.  Infections during bloom result in dead, dried up flowers or small, hard dried up fruit.

ANTHRACNOSE DISEASES OF STRAWBERRY
Species C. fragariae C. gleosporoides C. acutatum
Most common symptoms on strawberry

-Crown rot
-Petiole and runner lesions
- Black leaf spot

-Crown rot
-Irregular leaf spot

-Fruit rot

Host plants
Mostly strawberry
Many hosts Many fruit and vegetable hosts including apples, blackberries, tomatoes, peaches, blueberries

All species can cause similar symptoms, laboratory diagnosis required for positive identification.

Often Confused With
Botrytis Grey Mould (Botrytis lesions on fruit are usually associated with the calyx, lesions develop grey fuzzy spores.)
Leather Rot (Lesions are indistinct, smell foul, spores which may develop are white.)
Verticillium Wilt (Plants wilt and collapse, but crowns, when cut lengthwise, do not show reddish discolouration.)
Phytophthora Crown Rot (Plants wilt and collapse, and crowns, when cut lengthwise, show reddish discolouration.  Phytophthora is more common in Ontario than anthracnose.)

Biology
Anthracnose is a fungal disease that infects fruit, petioles, runner and occasionally crowns.  It is most likely introduced into new plantings by previously infected strawberry plants.  It can also overwinter for approximately one year on plant debris.  Some species of Colletotrichum infect weeds, and several vegetable and fruit crops, however, these are considered to be minor sources of inoculum compared to strawberry transplants.  Conidia are produced in warm, humid weather and are spread mainly by splashing rain and irrigation water.  People and equipment moving through the field can also spread anthracnose conidia to new locations.  If the plant surface is wet, conidia will infect.

Period of Activity
The fungus can be present at any time in a strawberry field, in infected plant debris or on symptomless plants.  Even though conidia may be present, anthracnose outbreaks are very weather dependent.  Infection is favoured by warm, humid weather and splashing rain or irrigation, especially between bloom and harvest.  Day-neutral varieties are more likely to be exposed to these conditions because they fruit during the warmer summer months.  Plasticulture systems favour the rain splashed spore dispersal of this disease.  Both day-neutral and plasticulture plantings are at higher risk of anthracnose than June-bearing varieties.

Scouting Notes
Scout for anthracnose when rain is followed by hot, humid conditions. Watch for brown dried up blooms and brown lesions on fruit.  In late summer scout for runner lesions in both established and new plantings.

Spore germination and infections requires 100% relative humidity.  Warm to hot temperatures (20- 32°C or 68- 90°F) are optimum for disease development.

Thresholds
None established.  Treatment decisions are based on field history and weather conditions.

Management Notes

  • Purchase plants from an accredited program.
  • Remove infected fruit from the field during harvest.
  • Work in infected fields last.
  • Clean clothing and equipment after work in infested fields.  Spores can survive for several weeks on clothing.
  • Use straw mulch to reduce rain splash.
  • Use of drip irrigation rather than overhead sprinklers can reduce disease spread.
  • Clean up crop debris between crops.
  • Vigorous plants high in nitrogen seem to be more susceptible to this disease, so avoid over-use of nitrogen.
  • Fungicides can be used to help manage this disease.
  • Resistance has been incorporated into some varieties but most common varieties are susceptible.