This week an apple sample from Frederick County Virginia was brought to our laboratory with a problem that is unusual but not unheard of: Phytophthora infection of low-hanging, green fruit. Phytophthora cactorum is a causal organism of collar rot of apple but also infects several other hosts. Note the zoned appearance of symptoms on some fruits, likely a result of the effects of light and dark on its growth pattern.
It is likely that swimming "zoospores" splashed up from the soil surface with heavy wind-driven rains and caused this infection within the past two weeks. EBDC fungicides, applied in the early cover sprays, should have helped to suppress this occurrence, although the residues would wear off quickly with heavy rains.
