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The
dictionary defines ecology as "the area of science dealing with the
inter-relationship of organisms and their environment." As compared
to other types of agricultural production, pasture ecology is
particularly interesting and complex because it involves animals,
plants, soil and the many climatic and environmental factors that affect
them.
A
livestock producer has many problems and opportunities to deal with on a
daily basis, so it may be difficult to find the time to think about the
whole picture. Yet, an overall awareness and understanding of the
influences that shape pastures is necessary to be a good manager. This
article, which deals with pest influences, is the second of a series
that deal with pasture ecology
Insects-
Thousands of species of insects can damage the forage species used in
the South. In most cases, this damage is relatively minor and does not
justify treatment, but there are many exceptions. In general, high value
crops such as alfalfa, or seedling forage crops that do not yet have a
good root system and that cannot tolerate extensive damage are those on
which the use of insecticides can be most easily justified. Advances in
variety development have resulted in resistance to some insect pests.
Diseases-
Most diseases of forage crops are highly specific and attack only a
particular forage species. In addition, diseases are usually most likely
to occur, and are most damaging, when plants are already weakened by
other stress factors. The possibility of disease problems increases the
desirability of using mixtures of species when feasible. For example, a
producer in the Deep South who is establishing a winter annual pasture
reduces risk slightly by planting mixtures of wheat and rye as compared
to either species alone. Resistant varieties are the best means of
control of forage diseases, but cultural practices also play a role in
reducing the incidence of some diseases.
Weeds-
Weeds are a
particularly common pasture production problem. In addition to lowering
pasture yield, quality, and/or stand life, some weeds are toxic to
animals. All the influences that affect forage plants in a pasture also
affect weeds. When a livestock producer manages pastures in such a
manner as to favor desirable forage species, a situation is
simultaneously being created that has an adverse effect on most weed
species. This is simple, but extremely important pasture management
concept.
Nematodes-
Nematodes are microscopic organisms that live in the soil and parasitize
the roots of various types of plants, including forage crops. The
primary damage nematodes cause is to upset the efficiency of moisture
uptake by plants. Consequently, plants that have shallow root systems
and/or that are being grown in locations in which moisture availability
is marginal are most susceptible to nematode damage.
Cool
season perennial species are severely penalized by nematodes when grown
on sandy soils. Other crops such as bahiagrass and bermudagrass are more
tolerant of nematodes, primarily due to a deeper and more extensive root
system. Warm season forage species also apparently tend to be less
preferred by nematodes. A few forage crops are resistant to certain
nematode species.
Conclusion
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