Page 79 - ORNAMENTALES DEL TRÓPICO

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identiFication and management oF ornamental Plant disease ProBlems

Immunity is the rule in the plant kingdom; most plants are immune to most pathogens.
Therefore, one does not have to worry that the black spot on roses will next appear on the

garden tomatoes. Plant breeders strive to select varieties of host plants that have resistance to

plant diseases. Many hybrids of ornamental plants have been developed that have some level

of resistance. Merely choosing and planting these hybrids will cut down disease problems.

There are also varieties that show more tolerance for a disease. The plant may seem to have

as many symptoms as the plant that is not tolerant, but somehow will still thrive and produce.

There are cultural methods that can be used to help control disease. These include sani-

tation, crop rotation, host eradication and improvement of crop environment. Sanitation invol-

ves removal of diseased plants and plant parts from the area to prevent spread of the pathogen.
As stated above, most pathogens are fairly host specific. By rotating or diversifying from season

to season, populations of the pathogen will decrease because one aspect of the disease triangle

- the host - has been removed. Sometimes, the weeds surrounding a field also act as hosts for

a particular pathogen. By eradicating these weeds, a possible host has been removed.

Watering only the soil around the roots of plants is preferable to wetting the foliage. It

is not necessary to wet the leaves. It is also important to water after the dew has dried, but

early enough to allow for fairly rapid drying of the irrigation water. The late morning hours are
a good choice for watering and if practiced can eliminate a lot of foliar leaf pathogens.

As was mentioned earlier, some pathogens can be carried from plant to plant on hands

and tools, especially pruning tools. It is very important to make sure plants introduced to the

nursery or landscape are disease free. This is especially important for bacterial diseases. It is not

uncommon to find infected liners being introduced into the production nursery. It is important

to disinfect hands and tools that are used with the plants. A 10-20 % solution of household

bleach in water makes a good disinfectant. Rubbing alcohol from the drug store will also work.

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