Research commissioned on behalf of multi-national companies and involving
laboratory bioassays and screening of chemicals by means of field trials is
conducted on an ongoing basis. Control efficiency is evaluated in open-topped
field enclosures and by caging samples of sprayed locusts immediately after
treatment. Rates of knock-down and mortality are continuously recorded at fixed
time intervals up to 72h post application. All relevant meteorological data is
recorded both at the time of application and throughout the post application
period.
Current preventative control methods for locusts rely exclusively on applying
broad-spectrum insecticides. Standard application practice is to deliver the
insecticide by means of ultra-low-volume (ULV) sprays. However, such spraying of
pesticide is now being viewed with increasing concern by landholders and
conservationists because of possible environmental damage. Considerable efforts
are being made worldwide to find safer alternatives.
Baiting
Baits offer a practical and ecological attractive alternative method of
controlling small to medium-sized locust outbreaks and probably also for direct
crop protection by farmers. South Africa pioneered the use of insecticide baits
for locust control. Baiting offers one method of presenting a toxic dose to a
pest at the same time limiting the numbers of non-target organisms coming in
contact with the pesticide. In the search for more environmentally acceptable
alternatives the role of baits in brown locust control are being re-examined.
Broadcasting moistened bran bait by hand in a ±1m wide barrier around the roost
in the early morning, has proved a most effective manner of baiting. When
applied in a manner that ensured direct interaction with the target, such as by
exploiting the basking and aggregation behaviour of locusts coming off their
roost in the morning, effective control has consistently resulted. Furthermore,
because only a relatively small strip is treated with bait, with no fall-out of
spray in the adjacent downwind area, environmental contamination is greatly
reduced.
Although labour intensive, baiting by control brigades hired on a temporary
basis could involve rural communities and thereby create jobs and strengthen the
economies of these areas. Small scale band control by means of such baiting
technology could complement the mainstream ULV ground spray operations and thus
be successfully integrated into the present locust control strategy. The ease of
bait preparation and simple low cost application which does not require
specialised equipment makes baiting an attractive method of locust control in
resource poor communities.
Barriers
The technique of spraying persistent organochlorine insecticides, such as
dieldrin, on to narrow strips of vegetation as a barrier against hopper bands
was extensively used in Central and North Africa in the past against the Red
Locust and the Desert Locust, but was never used against the Brown Locust.
However, a new generation of insecticides, with good persistence on vegetation
but without the bio-accumulation problems associated with the organochlorines,
is now available. The efficacy of barrier treatments against the fast-marching
Brown Locust hopper bands in the Karoo, with its sparse vegetation cover is
being evaluated.
Contact: Roger Price, pricer@arc.agric.za
