Fruit Crop Ecology and Management - UVM Apple Orchard

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generally invade commercial
orchards from nearby infested
hosts where the pest is not
controlled. Consequently, they
are frequently in clumps within
the orchard, with most
individuals near the border.
Appropriate management
strategies for apple maggot
may include placing all
monitoring traps along the
border and treating only the
borders with insecticide.
In contrast, spores of grape
powdery mildew are easily
dispersed over large areas by
wind, resulting in a relatively
uniform distribution of disease
in a vineyard. Therefore the
entire vineyard needs to be
protected from this disease.
Fruit Crop Ecology and Management: Chapter 2
Population genetics
An individual organism’s genes
determine its physical and
behavioral traits. Genes are
made up of chemical
messages or codes that dictate
which proteins a cell produces.
Particular combinations of
these proteins and environmental
cues determine what an
organism looks like and how it
Only the borders of this orchard are being sprayed for a pest
that is found along the orchard perimeter.
R. VanderPoppen
behaves. When individuals
reproduce, they pass along
unique combinations of genes
to their offspring. Different
environments favor individuals
with different physical and
behavioral traits. Individuals
with genes that improve their
survival will be more likely to
pass along these genes than to
the rest of the population. The
mix of genes in a population is
called the gene pool. The
composition of the gene pool
continually changes over time
through a process called
natural selection.
With the help of plant breeders,
fruit growers have taken
advantage of the gene pool’s
natural variability in a process
known as artificial selection.
The first step in this process is
to identify desirable traits, such
as flavor, color, or tolerance or
resistance to a pest. Once
desirable traits are identified,
these can be incorporated into
new crop varieties through
conventional breeding or
genetic engineering. For
example, apples have been
bred to create a few varieties
that are resistant to apple scab.
Even without specific breeding
efforts, fruit crop varieties
display a natural range of
resistance to various pests and
diseases. When monocultures
of single varieties are planted,
efficiency of production is
traded for diversity of
resistance to pests.
Repeated use of the same
class of pesticides to control a
pest can cause undesirable
changes in the gene pool of a
pest leading to another form of
artificial selection, pesticide
resistance. When a pesticide
is first used, a small proportion
of the pest population may
survive exposure to the