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September 2017
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The importance of insect rearing
F
ood security is a great concern with
the growing global population, which
in turn demanded an increase in food
production. Because of this high de-
mand, the impact that insect damage has
on crop production needs to be reduced.
To produce food of high quality and quan-
tity it is necessary to protect crops against
the most economically important insect
pests to minimise damage and crop loss.
By implementing an integrated pest man-
agement strategy, a sustainable method
can be achieved to control key insect pests.
In research, the insect pest must be investi-
gated using high numbers of individuals to
evaluate all potential control methods. That
is why mass rearing of insects is such an
important part of conducting research, to
achieve the best results.
At ARC-Grain Crops a number of maize eco-
nomical important insect pests are mass
reared under controlled conditions with the
purpose of evaluating chemical insecticides,
seed treatments, cultivars and genetically
modified crops against key insect pests.
In other instances, plants can be screened
for resistance to insects, indicating plants
that tolerate insect damage better. The in-
sect pests reared are the four most impor-
tant stem borer species in Africa, the Africa
maize stem borer (
Busseola fusca
), Chilo
borer (
Chilo partellus
), sugarcane borer
(
Eldana saccharin
a) and the pink stem borer
(
Sesamia calamistis
).
The Africa bollworm (
Helicoverpa armig-
era
), common cutworm (
Agrotis segetum
),
false wire worm (
Somaticus angulatus
) and
the fall army worm (
Spodoptera frugiperda
)
are also some of the common insect pests
reared at this facility.
To enable insect rearing in the laboratory,
insects must be sampled and collected in
the field. Specific requirements such as
temperature, humidity, photoperiod (day/
night length), sanitation, food and popula-
tion size are specific to each species and
need to be regulated.
Artificial diets are implemented for the con-
tinuous rearing of insects all year round.
However, contamination of these diets is of-
ten of huge concern that can only be curbed
by limiting any human exposure and access.
Important information can be observed
while rearing insects for example their
lifespan, duration of life stages, feeding be-
haviour and preferences, reproduction and
the effect of biotic factors such as cold on
the insect.
Susceptibility to biological and chemical
insecticides can be monitored and can give
early warning if resistance develops within
a pest species. Important discoveries are
made by monitoring insect pests, for ex-
ample the migration of different stem borer
larvae vary significantly between species.
One pest may spread across a greater dis-
tance faster than another species.
Some insect pests like the African maize
stem borer have a short life cycle and may
occur several times throughout a growing
season. This stem borer species also have
the ability to overwinter in maize stub-
bles and emerge after the first spring rain.
Behaviour and preference studies give
better insight to preferred conditions and
host plants.
Insights into the reproductive preferences
of insect pests assist with host plant resist-
ance. This means that if it is found that a
host plant is unacceptable to a female moth
wanting to lay eggs, she would rather move
to a more suitable host plant. Information
such as this can be used in interference con-
trol methods to control that specific pest.
Biological control methods are a big part of
integrated pest management. Therefore, in-
sect mass rearing is also important to have
great quantities for release of beneficial in-
sects such as parasitoids and predators that
can then suppress pest insect colonies.
An example of such beneficial insects
can be observed in the field in stem borer
populations where the small parasitic wasp
Cotesia flavipes
, parasitise larvae and su-
press pest numbers.
Knowledge obtained from insect rearing fa-
cilities are published to inform producers.
With this information, the producer can take
informed decisions regarding management
strategies including biological control, as
well as the use of resistant varieties. This
knowledge enables producers to develop
sustainable, integrated pest management
programmes.
For more information contact
Elrine Strydom at
strydome@
arc.agric.za
.
FOCUS
Integrated pest control
Special
ELRINE STRYDOM,
ARC-Grain Crops, Potchefstroom
1: Africa maize stem borer (
Busseola fusca
).
2: Chilo borer (
Chilo partellus
).
3: Sugarcane borer (
Eldana saccharina
).
4: Pink stem borer (
Sesamia calamistis
).
5: Common cutworm (
Agrotis segetum
).
6: Fall armyworm (
Spodoptera frugiperda
).
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