Beneficial Insects
In Fruit
Orchards
Before biological control,
farmers had to resort to
heavy and frequent spraying with pesticides to control this
caterpillar pest of fruit trees.
This caterpillar is a serious pest
in fruit tree orchards. It has
a big appetite for the leaves and fruit of apple, pear, and cherry trees. It is, therefore capable of causing
a lot of damage in a short time if not controlled.
USDA and Washington State
scientists have
successfully enlisted the help of a tiny,1-2mm
length wasp
to control a caterpillar pest.
How The Wasp Attacks The Enemy
The natural enemy of this caterpillar is the predator wasp,
Colpoclypeus florus, which is a tiny, little insect. The female wasp attacks by carefully
approaching the caterpillar from behind; and then stinging the caterpillar
behind the head, injecting a toxin while doing that. The little wasp must be quick and nimble doing this;
and be extra careful because she
is attacking a caterpillar that is a giant
compared to her size. The caterpillar can
get very aggressive
with this unwelcomed intrusion and
attack back. This is similar to a battle between
David and Goliath.
The injected toxin induces the caterpillar to produce extra webbing around itself.
The female wasp then lays her eggs
in the
webbing that
the caterpillar had created in response
to the toxin. Eventually, when
the eggs hatch and develop into larvae, they swarm towards the caterpillar and eat it up alive.
Bed And Breakfast
In studies done on fruit pests, scientists
were
curious about the large invasion of parasitic wasps
in
fruit orchards during spring time and where they came from.
The arrival of this large population of wasps
appeared
to have perfect timng
with the buildup of
the
caterpillar fruit pest.
This type of timing appeared too good to be true.
At first, scientists were not able
to figure out how this
wasp buildup could happen so quickly. They soon discovered the clue.
They found that wild rose bushes
growing next to their
fruit orchards were actually harboring great numbers of these parasitic wasps. It became clear that these rose bushes protected and served as a safe haven
for them during the winter months. As a result, these wasps lived through the winter months
with little
winter kill. At the same time, these rose bushes were also home for
another kind of caterpillar - the strawberry leaf roller, that the wasps
dine on during the winter
months. With bed and breakfast readily
available, these wasps can easily over winter easily without much casualty.
In early spring, these parasitic wasps leave the
rose bushes and take off for neighboring fruit orchards in great numbers. Their
appearance is perfectly timed with the population buildup
of the caterpillar pest.
Realizing this, growers are now actively nurturing wild
rose plants
around
their orchards; when in the past, these
bushes have been regarded as weeds and
routinely
mowed down.
Source:
Rose Gardens make Fruit Orchards More Inviting to
Friendly
Wasps. (2004) Jan. 24. Agric. Res. Magazine.
