Biological 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:

• http://r.search.yahoo.com/_ylt=A0LEVjp81C5VIPEAVzgnnIlQ;_ylu=X3oDMTEzaG5uYmtlBHNlYwNzcgRwb3MDNgRjb2xvA2JmMQR2dGlkA1lIUzAwMl8x/RV=2/RE=1429161212/RO=10/RU=https%3a%2f%2fstore.extension.iastate.edu%2fProduct%2fpm914-pdf/RK=0/RS=0JuVzjkbTNBJy._DBER6cPVJ5Kw-
• http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74133.html
• http://www.idtools.org/id/citrus/diseases/factsheet.php?name=Phytophthora
• https://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/Phytophthora.aspx
• http://pnwhandbooks.org/plantdisease/pathogen-articles/pathogens-common-many-plants/oomycetes/diagnosis-and-control-phytophthora-diseas-1
• http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3059.2009.02088.x/abstract
• http://openagricola.nal.usda.gov/Record/IND90052001
• www.bto.org/sites/default/files/u196/downloads/rr568.pdf
• www.agriculturejournals.cz/publicFiles.69621.pdf