parasitic pathogens
“
Parasitic diseases require three essential factors
before they infect plants: a susceptible host
plant, a live parasitic agent and an environment
favorable to disease development.”
including fusarium, verticillium wilts,
a number of viruses, certain leaf spot
pathogens and others.
With cucumbers and melons, selecting
varieties resistant to powdery mildew
will avoid many problems with these
plants. If a particular pathogen has
become an ongoing battle, checking
out what genetic resistance is available
in hybrid cultivars is worth the effort.
Environmental Factors – The growing
environment is often the main contributing factor to a disease outbreak.
Many fungal and bacterial diseases,
although not all, need either high
humidity or water on the plant for
them to successfully invade tissues. This
is why ventilation, with air movement
up, under and across foliage, and good
moisture removal, are so important
within enclosed growing areas.
Keeping things clean is another way of
thwarting pathogens before the infection process can begin. Used growing
media and old plant debris can harbor
disease pathogens for a considerable
length of time. Keeping the system
clean, removing prunings and old or
sick plants helps reduce the level of
pathogen inoculum in the growing
area. Avoiding heavy algae buildup and
controlling fungus gnats, which carry
plant diseases such as pythium, is also
important in hydroponic systems, as is
choosing a high-quality water supply
that is not contaminated with soil or
other organic matter.
Signs & Symptoms
Once a pathogen is inside the plant,
there are three main ways the plant
will respond during this initial phase of
infection: development of galls, swellings or leaf curl; the stunting, yellowing
or incomplete development of leaves,
fruit and roots; or plant tissue die-off,
such as blight, leaf spots, wilting and
rots, including root browning and disintegration with certain pathogens.
Sometimes this initial phase of infection inside the plant is not that visible
and growers may miss the early signs.
Powdery mildew is identified by white spore growth on leaves and stems.
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Maximum Yield USA | April 2015