A recent example of a successful disease-monitoring program
for an economically important crop is the soybean rust (SBR)
monitoring effort within North America. SBR, caused by the fungus
Phakopsora pachyrhizi Sydow, was first identified in the continental
United States in November 2004 (59; Sidebar 1: Soybean
rust disease cycle). SBR causes moderate to severe yield losses
globally (6,25,42,54). The fungus produces foliar lesions on soybean
(Glycine max Merrill) and other legume hosts. P. pachyrhizi
diverts nutrients from the host to its own growth and reproduction.
The lesions also reduce photosynthetic area. Uredinia rupture the
host epidermis and diminish stomatal regulation of transpiration to
cause tissue desiccation and premature defoliation (Fig. 1) (6).
Severe soybean yield losses can occur if plants defoliate during the
mid-reproductive growth stages
monitoring programs have been developed for several plant diseases,
including downy mildew of cucurbits, Fusarium head blight
of wheat, potato late blight, and rusts of cereal crops