Published: 09/07/2006 - Updated: 11/19/2016
During the locust plague of 1988, swarms of insects crossed the Atlantic from Mauritania to the Caribbean, flying 5 000 miles in ten days. The scientists were surprised, as swarms of locusts normally stop to rest at night, but if they do not know swimming, how they managed to swim across the ocean?
They discovered that they stopped to rest every night. On any ship that succeeded in finding, but also directly on the sea surface. Locusts in the first landing in the water drowned, and their corpses were floating in a raft on which the rest of insects rested.
Since the beginning of agriculture, more than 10 000 years, mankind has had to face a formidable and daring enemy: the Schistocerca gregaria, the desert locust. Although usually live alone in the deserted areas that stretch from West Africa to India, from time to time these insects get together in huge and voracious swarms that spread hunger and poverty where they spend.
Throughout history, farmers and governments have made repeated attempts to eliminate these flocks by catching insects, through the noise, smoke, and burning or burying swarms. But these measures have not had much success. With clouds that sometimes stretched for hundreds of kilometers, consisting of billions of individuals, destroy everything in their path by sheer numerical superiority.
The man has wondered since immemorial time about the origin of these insects and how they manage to survive. Only in the mid-twentieth century, it was realized that the same insect lone light brown which lives in the desert is the same species as the red and yellow locust plagues.
Once their biological characteristics were studied and began to spread the aerial a few decades ago, we began to make efforts to combat the locusts. But the use of pesticides on a large scale also is a risk for human health and the environment.
From the Emergency Center for Locust Operations (ECLO, for short) on the seventh floor of the headquarters of FAO in Rome, Keith Cressman, locust expert, monitors data on populations of insects that appear in the three computer screens on his desk. The last major offensive locust in the desert ended in early 2005 and since then the alert level is green, meaning that the situation is calm.
However ECLO experts are ready for the next battle in a long battle against the locusts. "Next time," says Cressman, “ We will have new weapons."
New Biological Weapons
Recent advances in research on biological pesticides, together with better surveillance and reporting, could take the war into a very different turn. These products can help to greatly reduce the use of chemical pesticides.
One factor is promising research currently being carried out by the International Center for Physiology and Ecology of Insects (ICIPE) in Nairobi. A team of the institution, led by an expert from Tanzania, Ahmed Hassanali, has identified and synthesized a pheromone-a chemical signal-specific sexual attraction of locusts that can be used against insects with a devastating youth impact.
Phenylacetonitrile, or PAN for short, is a pheromone that normally controls the behavior of adult males, who also used to warn other males to leave them in peace for mating. But as Hassanali discovered, it has very different effects among the young locusts, which do not yet have wings.
While adult locusts gather in swarms, the young, if given the right conditions, leave to behave individually and in flocks up to about 5 kilometers long.
Three separate test fields - the latest in Sudan last year, Hassanali's team showed that even small doses of PAN were able to stop and disperse the clouds of young locusts.
PAN makes insects break and return to a solo performance. Disoriented, some of them lose their appetite, while others turn into cannibals and eat their mates. The survivors were easy prey for predators.
What makes PAN particularly attractive is that it requires only a fraction, usually less than 10 millimeters per hectare in normal quantities of chemical or biological pesticides. This translates into a cost much more content: 50 cents per hectare, compared to $ 12 for chemical pesticides or 15-20 dollars for biopesticides.
This is definitely an element of great importance to countries in the frontline of the war against locusts, many of whom are among the poorest in the world.
Another bioweapon different but highly effective is Green Muscle ® (literally "Green Muscle") a biopesticide developed by the International Institute of Tropical Agriculture in Cotonou, Benin, and produced in South Africa.
Its active ingredient is spores of the fungus Metarhizium anisopliae varacridum, which germinate in the skin of young locusts and puncture to their skeleton, destroying tissue from within. Bad news for locusts as the fungus has no effect on other life forms.
Although Green Muscle ® is already used successfully in Australia, its introduction in Africa and Asia is delayed by several factors. These include the need for further large scale trials, the formal adoption of the product in different countries and that has a very short life in liquid form, ready to be sprayed. Another disadvantage is that it takes several days to kill the locusts. Furthermore, it is relatively expensive and would have to organize their mass production.
One possible solution would be to store the product in powder, to dilute it just before use. To try to lower costs, the team has found that used in combination with a small amount of PAN, only needs a quarter of the normal dose of Green Muscle ®.
Regulators for Insect Growth
Within the modern weaponry to fight the locust also highlights a number of products known as Insect Growth Regulators (IGR, for short), which regulate the ability of insects to change skin and grow. Moreover, there are no toxic effects on vertebrates.
The IGR are effective for several weeks after application and are used in the treatment of so-called "barrier". This method consists of narrow bands of pesticides applied in perpendicular to the direction of movement of insects. You only need a 10 per cent of the amount used in a blanket treatment. Having passed one or two of the barriers, insects absorb enough pesticide to cause death while moving skin.
As with PAN and Green Muscle ®, the IGR should be used on locusts at an early stage of their development, before they begin to fly. This in turn requires a high level of vigilance and an update to be sure that any concentration of locusts is destroyed at its roots.
Although the account Cressman ECLO satellites, computers and mathematical models at its disposal, the weak link in the chain has always been the time taken to obtain reliable information from the field.
Displaced mobile teams on the ground makes responsible keeping track of the active population of locusts in the most remote places and often more hostile world, taking into account the environment and safety. You can spend a week from that information, say, the central Sahara, come to the table Cressman. At that time, the locusts "do not require a visa," the expert stressed, may have been moved to another country or even another continent.
However, this situation will change soon. Field teams are being equipped with special devices able to obtain vital data on the locust and the environmental conditions and make them central to their bases and in Rome in real time.
Developed by the French Space Agency (CNES), there is the eLocust2, a device capable of sending information to communications satellites and make it to national locust control in affected countries after a few minutes. And then the release of Cressman for analysis. In case of extraordinary concentrations of insects, you can take urgent initiatives, ensuring that the locusts never develop enough to reach to form swarms.
In an article published in Science magazine, locust expert Martin Enserink gave a graphic description of the devastation caused by the plague in Morocco:
"On a beautiful November morning is clear, even from afar, something strange happens in trees around a small village. They are covered with a bright pink, as if its leaves are changing color.... When one approaches, the hue becomes a winding mass, a cloud of insects on every tree, devouring the leaves, even closer, you hear a soft drizzle: the incessant flow of locust droppings falling to the ground."
These nightmarish scenes, along with the plagues of locusts, could become a thing of the past day.