PPDL Picture of the Week
August 19, 2019
Dan Egel, Clinical Engagement Associate Professor-SWPAC, Botany and Plant Pathology, Purdue University
There are many reasons why a cucumber
plant might wilt as can be observed in Figure 1. Of course, plants may wilt if there is not
enough water. If insufficient water was the cause of the wilt in Figure 1, one
might expect to see the entire row of cucumbers wilting. Instead, Figure 1
shows just one plant wilting. And the soil around the plant was sufficiently
moist. A second reason that a cucumber plant might wilt is the disease
bacterial wilt spread by cucumber beetles. However, no beetles or beetle
feeding were observed. One might guess that there was a root problem that
caused the cucumber plant to wilt. As one knelt to start to investigate a root
problem, the base of the plant would reveal the symptoms of charcoal rot
Charcoal rot is caused by the fungus Macrophomina phaseolina. This fungus can survive several years in
the soil without a host. In addition, several hosts have been listed for this
disease including strawberry, sorghum, potato, corn and soybean. This is the
first time that cucumber has been listed as a host in Indiana. Charcoal rot is
favored by hot, dry soils. Apparently, the environment in this high tunnel
were favorable for the disease.
of charcoal rot is dependent on crop rotation with less susceptible hosts.
Plants should be managed so as to avoid stresses such as fertility, irrigation
and other diseases. Some varieties may be less susceptible to charcoal rot.
you suspect charcoal rot, be sure to get an official diagnosis.