Forest
pests present a significant problem because it is not easy to access the canopy
and monitor pest populations. In addition, forestry pests such as bark beetles,
kept under control by natural enemies in their native range, may be transported
large distances in cut timber to places where they have no natural predators,
enabling them to cause extensive economic damage. Pheromone traps have been used to monitor pest populations in the
canopy. These release volatile chemicals that attract males. Pheromone traps
can detect the arrival of pests or alert foresters to outbreaks. For example,
the spruce budworm, a destructive pest
of spruce and balsam fir, has been monitored using pheromone traps in Canadian
forests for several decades. In some regions, such as New Brunswick, areas of
forest are sprayed with pesticide to control the budworm population and prevent
the damage caused during outbreaks.
Biological pest control: Biological pest control is a method of controlling pests such
as insects and mites by using other organisms. It relies on predation,
parasitism, herbivory or other natural mechanisms, but typically also involves
an active human management role. Classical biological control involves the
introduction of natural enemies of the pest that are bred in the laboratory and
released into the environment. An alternative approach is to augment the
natural enemies that occur in a particular area by releasing more, either in
small, repeated batches, or in a single large-scale release. Ideally, the
released organism will breed and survive, and provide long-term control.
Biological control can be an important component of an integrated pest management
programme.
Cultural
paste control: Mechanical
pest control is the use of hands-on techniques as well as simple equipment and
devices, that provides a protective barrier between plants and insects. This is
referred to as tillage and is one of the oldest methods of weed control as well
as being useful for pest control; wireworms, the larvae of the common click
beetle, are very destructive pests of newly ploughed grassland, and repeated
cultivation exposes them to the birds and other predators that feed on them. Crop
rotation can help to control pests by depriving them of their host plants. It
is a major tactic in the control of corn rootworm, and has reduced early season
incidence of Colorado potato beetle by as much as 95%.
Chemical
method: Pesticides
are applied to crops by agricultural aircraft, tractor-mounted crop sprayers,
aerial spray by modern aircraft or as seed dressings to control pests. However,
successful control by pesticides is not easy; the right formulation must be
chosen, the timing is often critical, the method of application is important,
adequate coverage and retention on the crop are necessary. The killing of
natural enemies of the target pest should be minimized. This is particularly
important in countries where there are natural reservoirs of pests and their
enemies in the countryside surrounding plantation crops, and these co-exist in
a delicate balance. Often in less-developed countries, the crops are well
adapted to the local situation and no pesticides are needed. Where progressive
farmers are using fertilizers to grow improved crop varieties, these are often
more susceptible to pest damage, but the indiscriminate application of
pesticides may be detrimental in the longer term. The efficacy of chemical
pesticides tends to diminish over time. This is because any organism that
manages to survive the initial application will pass on its genes to its
offspring and a resistant strain will be developed. In this way, some of the
most serious pests have developed resistance and are no longer killed by
pesticides that used to kill their ancestors. This necessitates higher
concentrations of chemical, more frequent applications and a movement to more
expensive formulations.
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