Page 72 - ORNAMENTALES DEL TRÓPICO

72 Ornamentales del trópicO

Many insects, such as caterpillars and maggots (fly larvae) are fairly large and easily spotted.
Even smaller insects and related animals (e.g., mites and foliar nematodes) can be readily seen

with a 10x power hand lens. One of the reasons to consider insects early in the identification

process are the relative ease in finding the culprit associated with the damage.

“Abiotic” literally means without life. Therefore, abiotic plant disorders are those factors,

usually associated with the plants’ environment that may affect plants adversely. These envi-

ronmental factors include temperature, moisture, soil pH, air quality, light regime, and nutri-

tion. If one or more of these factors goes above or bellow optimum range for a given plant

species, injury might result.

One important piece of evidence in implicating an abiotic cause for injury to plants is
the distribution of the damage within the environmental unit. Plants generally grow in distinct

environmental units, whether it is a garden, a small shade house on the property, or a large

commercial field of pitahaya. Environmental problems are much more likely to affect all or

almost all plants in the environmental unit uniformly. Disease and insect problems, on the

other hand, tend to occur, especially early in outbreaks, in clumps or hot spots within the unit.

For example, if herbicide is sprayed to control weeds next to a row of containerized palms in

the nursery, injury will likely be uniform and all the palms in the affected row will likely show
symptoms. A fungal pathogen, in contrast, may produce similar dark discoloration of leaves,

but only on one or two plants in the early stages of the epidemic.

Many ornamental plants grown in southern Florida are quite sensitive to cold weather. This is

especially true of landscape and bedding specimens, such as heliconia, begonia, and many palm spe-

cies native to tropical areas. This damage may even occur above 32°F (0°C) on particularly sensitive

species. Freezing temperatures damage plants by inducing ice-crystal formation in or between cells.

Cell membranes are ruptured on contact with the sharp edges of these crystals and subsequently

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