Phytophthora

phytophthoraBiological information:

  • Common name: Phytophthora
  • Scientific name: Phytophthora sojae, Phytophthora ramorum, Phytophthora spp.
  • Family or class: Oomycetes

Symptoms and/or signs to watch out for:

  • Wilted leaves
  • Dull green, yellow, red, or purple leaves
  • Gummy sap oozing out of crown
  • Water-logged spots on roots
  • Dead seedlings
  • Loss of vigor

Life cycle:

  • Spores live in soil for years
  • Must have wet conditions
  • Germination of motile spores from resting spores
  • Infection of plant host

Mode of reproduction:

  • Zoospores
  • Travel through water
  • Resting spores germinate to produce motile spores for infection

Vectors for the pest:

  • Ants
  • Snails
  • Rainwater
  • Infected soil/leaf litter

Overwintering habit:

  • Lower survival rate in harsher winters

Alternate hosts:

  • Hairy nightshade

Horticultural production information:

Preventative strategies:

  • Regulate water levels
  • Proper crop rotation
  • tool/equipment sanitation
  • Resistant crop varietes

Threshold levels:

  • There is no threshold level for pigweed because it is so highly prolific.
  • One female plant can produce 150,000 seeds per year.
  • If 99% percent were killed, 150 still survive cause the same problem.

Control options:

Physical controls:

  • Break compaction
  • Plant on mounds
  • Remove infected bark

Biological controls:

  • Soil fungi
    • Trichoderma
    • Gliocladium

Cultural Controls

  • Keep water levels as close to field capacity or lower if possible
  • Increase drainage
  • Solarization
  • Equipment sterilization

Chemical controls:

  • Disinfect irrigation water
  • Fumigating for weed and insect control often helps control fungi and Phytophthora
  • Metham sodium can be applied through irrigation water
  • Contact fungicides to reduce infection
  • Copper based compounds

 

References:

 

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