290 M. BABADOOST
expression or after soil is saturated with excessive rain or irrigation. The
stems of infected plants turn light to dark brown near the soil line and
become soft and water-soaked. Infected stems collapse and die. The tap-
root and lateral roots of infected cucurbit plants usually do not exhibit
symptoms. Following death of the foliage, roots may give rise to new
vines if environmental conditions become less conducive for disease
development. Phytophthora damping-off may result in partial to total
loss of the crop.
Crown Rot. Phytophthora capsicialso causes crown rot primarily in
mature plants (Hausbeck and Lamour 2004; Islam et al. 2004). Crown rot
may occur in most cucurbits, but it is more common in pumpkins and
squash, particularly in yellow squash. After infection of the crown, a
watery rot of the tissue occurs; transport of water and nutrient to vines
ceases, leaf wilting progresses from the base to the extremities of the
vines, and the plant dies within a few days.
Vine Blight.Vines can be affected at any time during the growing sea-
son (Gubler and Davis 1996a; Latin and Rane 1999; Babadoost 2004;
Islam et al. 2004). Water-soaked lesions develop on vines. The lesions
are dark olive and then become dark brown in a few days. Lesions gir-
dle the stems, resulting in rapid collapse and death of foliage above the
lesion. Total vine losses byP. capsicihave been observed in the fields,
especially in pumpkin and squash fields (Babadoost 2000, 2004).
Leaf Spot. Phytophthora capsicialso can cause leaf spots of both the
petioles and the leaf blades of plants. Dark brown, water-soaked lesions
develop on petioles (similar to lesions on vines), resulting in rapid col-
lapse of the petiole and leaf death. Infected leaf blades develop spots
ranging from 5 mm to more than 5 cm in diameter (Babadoost 2004;
Islam et al. 2004). Infected areas are chlorotic at first, but within a few
days they become necrotic with chlorotic to olive-green borders. Under
wet and warm conditions, leaf spots expand rapidly, coalesce, and may
cover the entire leaf. Under dry conditions, leaf spots cease to expand.
Fruit Rot.Fruit rot can occur at any time from fruit set until harvest
and even in post-harvest storage (Gubler and Davis 1996a; Hausbeck
and Lamour 2004; Islam et al. 2004; Babadoost and Zitter 2009; Granke
et al. 2012). Fruit rot generally starts on the side of the fruit that is in
contact with the ground. However, occasionally infections will begin
in other locations on the fruit where infected leaves or vines come
into contact with a fruit. Also, symptoms on the upper surface of the
fruit develop following rain or overhead irrigation, which can splash
water containing the pathogen onto neighboring plants (Babadoost
2000; Babadoost and Zitter 2009). Fruit rot typically begins as a water-
soaked lesion. Lesions expand, and become covered with white mold.