- OOMYCETE DISEASES OF CUCURBITS 305
is a challenging task. At present, major practices for management of
oomycete diseases in cucurbits are using host resistance, cultural prac-
tices, and fungicide use.
Long-term strategies for effective management ofP. capsiciin cucur-
bits are yet to be developed. Management ofP. capsiciin cucurbits is a
challenging task. First, cucurbit cultivars resistant toP. capsiciare not
available. Second, although several relatively effective fungicides for
managingP. capsiciin cucurbits were developed in the past 15 years,
none of the available fungicides can protect plants againstP. capsiciin
continuous moist conditions (e.g., continuous rainfalls). Third,P. cap-
sicispreads by soil movement, running water, farm machinery, and
infected plant materials. Preventing spread ofP. capsiciis very compli-
cated. Fourth, effects of cultural practices have limited effect in man-
agingP. capsici, because crop rotation, using cover crops, use of the
mulches, planting on raised beds, and soil-drainage have not been reli-
able for management ofP. capsiciin cucurbits. AlthoughP. capsicidoes
not survive in the soil for more than 4 years, the pathogen has more than
50 hosts, including some weeds. Thus, crop rotation for management of
P. capsicimust be with effective control of weeds in the field, which is
not a very feasible practice in commercial fields. Overall, without using
resistant cultivars, effective management ofP. capsiciin cucurbits may
not be satisfactory. The current strategy for management ofP. capsici
is combining cultural practices with application of fungicides can be
effective in a dry year; with heavy rains, disease management is lim-
ited. Cucurbits resistant toP. capsicimay be developed by: (1) conduct-
ing worldwide screenings of all available domesticated and wild cucur-
bits for resistant toP. capsici, identifying resistant sources, and incor-
porating resistance in commercially acceptable cultivars; (2) inducing
resistance by treating seed or seedlings with certain chemicals, as has
been done in some other crops (e.g., tomato); and (3) genetic engineer-
ing of cucurbits by incorporating genes resistant toP. capsicifrom other
sources. For example, resistance toP. capsicihas already been identi-
fied in peppers, which may be considered a source for transgenic in
cucurbits.
Effective management of downy mildew of cucurbits by timely prac-
tices of available methods is feasible. First, some cucurbit cultivars
resistant to downy mildew are available. However, to overcome to
development of new pathotypes of the pathogen (P. cubensis), new
cucurbit cultivars with different resistant genes is essential. Second,
movement ofP. cubensisis monitored (or can be monitored) in cucurbit-
growing areas, which provides some information for protecting plants
against the disease prior to plant infection. Monitoring of movement
ofP. cubensisis feasible because the pathogen is an obligate parasite