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Leather rot of strawberry

Quick facts

  • Leather rot occurs now and then in Minnesota.
  • The disease infects flowers and fruit at all stages.
  • Infection starts as tan-brown patches on green fruit and purple-brown areas on ripe fruit.
  • Eventually, infected fruit develop a brown, leathery texture and then shrivel.
  • Infected strawberries have a unique unpleasant odor and a strong, bitter taste.
  • If making jam, a few infected berries can ruin the taste of a whole jar.
  • To manage this disease, plant in a well drained location, use mulch and drip irrigation, and keep your patch clean.

How to identify leather rot

Infected berries

Fruit symptoms

Infections on green fruit:

  • Part or all of the fruit turns tan to brown.
  • Sometimes the center of the infected area remains green and is outlined by a brown margin.
  • As the disease progresses, these unripe berries become completely brown and have a rough, leathery texture.
  • Eventually, the infected fruit dries and shrivels.
Infected berries

Infections on ripe fruit:

  • May cause little to no color change.
  • Infected areas may become pale, purple or brown.
  • Rot on ripe fruit becomes dry and leathery over time.
  • Eventually, the infected fruit dries and shrivels.

How does leather rot survive and spread?

  • Leather rot is caused by Phytophthora cactorum.
  • The leather rot pathogen is an oomycete; commonly called a water mold. These unique pathogens thrive in wet conditions and produce three types of spores.
  • Oospores are tough, resting spores that form in shriveled berries.
  • These spores can survive for many years in soil.
  • Oospores germinate when soils are very wet to produce zoospores and then sporangia. 
  • Zoospores are swimming spores.
  • They move through a film of water on the plant or soil to reach susceptible fruit and flowers.
  • Zoospores only need two hours of moisture on the plant surface to start an infection.
  • Once infected, sporangia are produced on fruit and are splashed by rain or irrigation to infect other fruit.
  • The leather rot fungus thrives in areas where water pools after rain.

How to manage leather rot

Choose a well drained location

  • Choose a planting site with good drainage or improve drainage before planting.
  • Improve drainage by adding organic matter to soil and redirecting water away from the area.
  • Consider planting strawberries on raised beds to improve drainage.

Use mulch, drip irrigation and good sanitation

  • Use straw mulch to keep berries from contacting soil and any puddled water. 
  • Mulch will also reduce splashing of spores from the soil up onto fruit and flowers.
  • Water through drip irrigation or a soaker hose. If overhead sprinkling is your only option, water early in the morning on a sunny day so leaves dry quickly after watering.
  • Pick fruit frequently and remove over ripe and diseased berries from the field.

Fungicides

  • There are no fungicides available to home gardeners that are effective in preventing leather rot.

Michelle Grabowski and Karl Foord,
Extension educators

Reviewed in 2019

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