DiseaseHigh Severity

Phytophthora Root Rot

Phytophthora spp. including P. ramorum, P. cactorum, P. cinnamomi, P. palmivora, P. citricola, P. nicotianae, P. ramora

A soil-borne oomycete pathogen causing crown rot, collar rot, root rot, and stem rot. The pathogen survives in soil for several years and is particularly problematic in poorly drained soils. Trees may die in one season or linger for multiple growing seasons.

Peak Season: Most active during cool, wet weather in spring and fall
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Phytophthora root rot showing characteristic root decay and canker symptoms

Identification & Symptoms

What to Look For

Cankers at or below soil line extending into root system
Brown, slimy bark when wet
Orange to reddish-brown cambium and phloem when bark is removed
Poor vegetative growth and reduced vigor
Chlorotic foliage that may turn purple in autumn
Girdling cankers around trunk base
Tree death ranging from one season to multiple years

Potential Damage

Disrupts water and nutrient transport through root system
Cankers girdle trees causing decline and death
Infection can invade trunk or main stem
May infect susceptible scions at bud union
Can kill trees in single growing season
Causes chronic decline over multiple seasons

Lifecycle

Fungus survives as thick-walled oospores in infected tissue or soil through cold weather and drought. Under moist conditions, oospores germinate forming sporangia. In free water, sporangia release motile zoospores that swim to and infect roots or lower trunks. Trees are most susceptible during bloom period.

Professional Treatment Approach

1

Improve soil drainage to reduce moisture

2

Avoid planting too deep

3

Fungicide injection for preventive treatment

4

Remove infected plant material

5

Improve air circulation around plants

6

Avoid overhead irrigation

Recommended Mauget Products

Fungisol

Professional-grade treatment specifically effective against phytophthora root rot.

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Tebuject 16

Professional-grade treatment specifically effective against phytophthora root rot.

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