parasitic pathogens
Disease Prevention
Host Plant Susceptibility – While disease spores may be
“
Parasitic or
infectious diseases
are those caused by
a living enemy—a
pathogen that
may be a fungus,
bacterium or virus.”
132
Maximum Yield USA | April 2015
Not all spots
are caused by
diseases. Potassium
deficiency, seen here
on this lettuce, is
often mistaken for
an infection.
present in and around a hydroponic system, if the plants are
strong and healthy, they may be less susceptible to an attack.
An overcrowded garden is extremely inviting for invading
pathogens. Overcrowded plants are often weakened by a lack
of access to light, and humidity can build inside and under
dense canopies, where air movement is restricted.
Host plants are also more prone to infection if they are
physically damaged, as this provides an open wound for
direct entry into the plant. Pruning cuts, leaf removal and
torn roots during transplanting all provide a moist surface
for fungal spores and bacteria. Over-watered plants with
saturated root systems are particularly prone to pythium and
other root rot diseases. Levels of dissolved oxygen in solution culture or NFT systems should be maintained at optimal
levels to help prevent root rot issues.
One further way of reducing host susceptibility to pathogens is with genetic resistance and this is one of the most
effective methods of disease prevention. Most plants are
prone to just a few significant pathogens—powdery mildew
in cucumbers and melons and wilt pathogens in tomatoes
being common examples. Many modern cultivars have
some degree of disease resistance bred into them and
these are well worth taking advantage of as it means higher
yields and less need for spray applications. Tomato hybrids
usually have resistance to a number of common issues,