A Different Approach
Locusts have an important role to play in nature,seasonally
(usually post-drought) improving the vegetation structure of grasslands,
providing a bountiful, nutritious source of food for wildlife and, in some parts of
the world, for people. These benefits cannot be ignored and, as can be seen by the
USA experience, plague locusts are much more vulnerable to extinction than could
have ever been predicted.
The difference between Locusts and many other issues effecting agricultural
crops, is that their effect is usually intense but brief. Locust swarms, commonly
the cause of damage to food crops, move rapidly across the landscape. This unique
behaviour should be able to be used positively to create ways to enable
agriculture and locust migrations to co-exist. There is a need to develop
environmentally sustainable ways of minimising the brief damage caused by
locusts, whilst still enabling the environmental benefits of locust migration to
occur.
Despite decades of "war with locusts", the enormous expense of aerial
spraying, and the cost and environmental damage caused by the chemicals, Locusts
still cause difficulties for agriculture in some parts of the world. Isn�t it
about time that other options were considered?
To date, despite the environmental benefits of Locusts and the
untold damage brought about by current control methods, there has been very
little research into anything that does not attempt to kill the locusts,
and seriously reduce the frequency or extent of a locust migration. The eventual
result of these methods will see the locusts become ever more resistant and more
expensive to control, or they may disappear entirely. Neither scenario is
desirable.
The following are a number of alternative management approaches that should
be investigated and could be the key to sustaining a healthy world, and a
healthy human population, in locations where Locusts are a natural part of
life.
- Repellents for high-value food crops.
- Timing of grazing of pastures, and
the planting and harvest of crops and fodder.
- Improved conservation of food and
fodder.
- The use of locusts as a source of
food for humans.
- Barriers to prevent damage by locust
swarms.
- Using behavioural science in
landscape-scale management to minimise any adverse effects of swarms on
agriculture.
Considerable food crop damage can occur from
swarming locusts that move rapidly across the landscape. Having eaten what they
want, which may or may not include a substantial proportion of a crop, they move
on. These swarms would naturally have continued across the landscape until they
terminate due to predation, climatic conditions, or lack of suitable food. Sometimes such swarms
finally drown in the ocean, or lakes after some gross miscalculations in long
distance migration. However migrations now have a new predator in the form of
humans, who have the technology and chemical insecticides to severely reduce the
insect swarms, and knock out the hoppers before the swarms even occur.
It is common for a locust swarm to be present in any one area for only a
matter of days, before the bulk of the insects move onto new ground. This fact
makes repellents an excellent choice of alternative management. Repellents need
only be strong enough to repel the locusts for a matter of days. There seems to
be very limited recent research in this aspect of control, except in India where
Neem Oil is suggested as a suitable product for this purpose.
If high-value food crops are protected from damage, the locusts would eat
only the green from low value pasture land. This does not present a significant
problem in most situations, with dry feed remaining and green feed re-sprouting
as soon as the locusts move on.
Locusts are a warm season insect. In many
districts, they do not hatch or start their migration until a certain time of
the year. In southern Australia at least, locusts are seldom seen until
conditions are dry and warm, and winter crops (wheat etc) are already mature and
of no interest to these green-eating insects. However, there are always
exceptions, such as a very late-sown (spring sown) crop, or a very early-sown
crop. If a locust problem is anticipated in any given year (ie, egg laying has
occurred in a district), sowing of the next winter crops should be held off
until the cooler weather, to avoid damage from potential Autumn locust
hatchings. Very late sown crops (spring-sown in winter rainfall areas) are
uncommon, always a gamble, and will be sown knowing that they are at potential
risk of damage from native locusts.
In other situations, where locusts threaten hay
crops, the hay could be cut early to avoid the damage. Although this will result
in a slight yield loss, it will also avoid damage caused by locusts, and the
cost of applying locust-control strategies. This may work out to be a more
economical solution.
Particularly susceptible pastures could be grazed
just prior to, or at the same time as the locusts arrive. In that way, the stock
will receive at least a proportion of the pasture. Once the locusts move on,
perennial, summer-active pastures will regrow and the negative effect will be
short term. If feed is scarce for a week or two, animals could be fed fodder
that has been stored in other seasons especially for such a purpose.
It may be possible to use grazing as a tool for
directing migrating locusts across a landscape. If an area surrounding a
valuable crop or pasture is grazed very hard before the locusts arrive, this may
act as a barrier to encourage the locusts to move across the landscape on a
different path and thus avoid damage to the high value crop.
Large locust plagues in Australia are infrequent.
Some documentation suggests that plagues coincide with post-drought conditions,
throughout the world. This would be 1 in 5 to 10 years in pastoral parts of
Australia, and less than one in 10 years in higher rainfall country. In good
years, fodder and grain can be stored for use when the need arises. Fodder could
be stored for the purpose of managing a Locust migration in the same way as it
is stored to manage the drought years.
In Australia, no one will starve due to a locust
migration. In other parts of the world where food resources are less reliable,
locusts may be an extra burden on an already strained community. The root cause
of this hardship is not the Locusts, more often being due to political and/or
economic conditions. These communities are least able to afford chemical methods
of locust control, and money thus expended could be used to greater advantage in
other projects. In improved circumstances, food and fodder conservation
strategies could be applied in these communities too.
If Australians could overcome an irrational fear of such a thing, eating
locusts is a very sensible suggestion. They are highly nutritious, very easy to
harvest and can occur in abundance. In some parts of the world, it is not uncommon to
see
locusts for sale as a food in markets, particularly in times of locust
plagues. Unfortunately, the use of insecticides in many of these countries
nowadays, means that people who used to utilize the Locust food source have been
told they can no longer do so. It is
feared that the locusts might have high pesticide residues.
At certain times, Locust swarms avoid treed areas. In Southern Australia
in Feb 2005, it could be seen that the swarms avoided lines of trees. In
this instance, they were seeking out their preferred nesting sites, which
obviously does not include densely treed areas. A line of trees could therefore prevent
damage by locusts in some situations.
Migrating swarms usually fly quite close to the ground (up to 3m). Only in
times of the very different "long distance" migrations do they fly high above
the ground. Nets therefore could potentially be used as barriers to prevent damage to high value crops.
In northern Victoria in November 2005, hopper locusts were often seen,
crowded into the corners of native grassland paddocks, or crowded on roadsides.
Their preferred habitat has become fragmented due to modern agricultural
practices, and the locusts seemed unsure where to go. Studies on other locusts
in other parts of the world have shown that this crowding is often the catalyst
to make locusts change their behaviour and stimulates migration. Barriers such
as roads and fragmented native vegetation could therefore be encouraging premature
migratory behaviour in locusts. It may be possible therefore to form Locust
corridors, much the same as other wildlife corridors to reduce this occurrence.
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