Root and stem infection can occur at or near the soil line as a dark green, water-soaked, mushy area that eventually turns brown and girdles the stem causing plant wilt and death. The pathogen progresses along plant vascular bundles and pith tissue. Branch infection may extend to petioles, leaves, blossoms or fruit that can become covered by a white moldy growth during high moisture periods. Infected fruits dry, remain attached to the plant and become mummified. Infected seeds turn dark and shrivel.
Similar symptoms occur on other vegetables such as squash.
Phytophthora infection of tomato fruits is called buckeye rot. A green to brown water-soaked spot develops near the blossom end of the fruit, especially if it is in contact with moist soil. When the rot develops slowly, definite zonations or dark concentric rings form in the decayed area of the fruit. A soft rot may develop from secondary bacterial invaders. A premature ripening or fruit-drop also may occur on infected eggplant.