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September 2018
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Importance of monitoring insects
in a management programme
T
he aim of a management programme is to prevent pest infes
tations in a crop. Managing insect pests requires flexibility
since insects are site, crop and area specific. Monitoring is
the routine inspection for the appearance of insects.
The goals of monitoring are to locate, identify and determine the
severity of pest infestations. This information can then be used to:
Determine the success of a current management strategy and
make adjustments accordingly.
Predict population growth and distribution patterns of insects.
Assess and predict future damage by an insect pest.
Information gained through monitoring will enable the producer to
make sound management decisions.
For monitoring to be successful, the scout needs to know exactly
what to look for:
Insect feeding damage symptoms on the plant. The feeding dam
age of the insect is often more noticeable than the insect itself.
Assess the severity of the damage. It is also important to deter
mine the plant parts where most of the damage is located. The
damage might be on a part of the plant where it will not affect
the yield of the crop. It is also important to note the growth stage
of the crop. Certain crops are more vulnerable at certain growth
stages. The seedling stage of wheat, for instance, will be vulner
able for insect feeding damage and heavy insect infestations at
this stage might affect the yield. Insect infestations after the flag
leaf stage will, however, not influence the yield significantly.
Determine what is causing the damage and whether the dam
age-causing insect is still present on the crop. Sometimes in
sects start feeding on the crop and cause initial damage and then
move on or are killed by natural enemies (predators, parasitoids
or pathogens) or environmental fluctuations. If the insect is still
present, follow-up monitoring will be necessary.
Determine the percentage infestation in the crop field and
whether the infestation is in isolated patches or spread through
out the crop.
Note other insects present in the crop field as well as their func
tion in the crop ecosystem, such as herbivores on the crop or on
weeds, predators, pollinators and decomposers.
Record the environmental parameters such as temperature,
wind, humidity, soil moisture and rainfall.
All these factors need to be considered carefully before a manage
ment decision is made. It is important to keep a dated record of all
these observations in order to be able to predict patterns of insect
colonisation and distribution throughout the growth season of the
crop. This can be very helpful in predicting future patterns of infesta
tion.
Advantages of a good monitoring system include:
Early detection of damage. This will facilitate timeous action and
prevention of further, possibly economic, damage.
Controlling the pest effectively during the most susceptible
stage of its life cycle.
Save costs by deciding on the best management action. Often,
when looking at all the observations, expensive chemical spray
ing might not be necessary. The cost of different management
actions has to be weighed against the potential loss of yield en
suring maximum profit.
Limit damage to the environment by unnecessary use of harmful
chemicals.
Enable target-specific management. Unless the pest is iden
tified, the control programme may have the wrong pest as its
target. Identification allows the treatment of the pest problem,
while avoiding injury to non-target organisms.
Identifying the effects of naturally present biological control
agents. This means knowing which organisms are beneficial and
determining how pests have been affected by them.
Assessing the efficacy of pest management actions that have been
taken is a very important part of monitoring. An efficient monitor
ing programme will enable producers to prevent or minimise pest
outbreak and economic damage to a crop and save costs due to un
necessary control.
Producers with any queries can contact the author
at 058 307 3431, 082 564 3795 or
jankielsohna@arc.
agric.za
.
Focus
Integrated pest control
Dr Astrid Jankielsohn,
ARC-Small Grain, Bethlehem
“
It is important to
keep a dated
record of all these
observations in order
to be able to predict
patterns of insect
colonisation...
“