Seasonal development
and life cycle—Phytophthora root rot
Phytophthora is a soil-inhabiting fungus that is favored by wet conditions. Species of Phytophthora
produce resting spores that survive for years in moist soil in the absence of a suitable host. When a
host is nearby and free water is present in the soil, resting spores germinate to produce motile spores
that can directly penetrate roots, branches, or crowns as long as free water is present. Resting spores,
decaying host tissue in the soil, and active cankers can all be sources for new infections. The fungus
can be spread in splashing rain or runoff water and by the movement of contaminated soil or plant parts.
Root rot of avocado, citrus, and tomato is favored by warm conditions; decay of crown, trunk, and branches
of other tree species is favored by cool, wet conditions.
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Rotting
of tomato stem
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