New biological methods of locust control

Locusts have long caused havoc in parts of West Africa, wiping out crops in a short time in areas already struggling with food security issues at the best of times. Aerial spraying of pesticides is not only expensive and often done too late to avoid widespread crop losses when locust swarms strike, but there have also been increasing concerns about their effects on human health and the environment.

There has been recent progress in the development of anti-locust biological control agents which hold the promise of reducing the necessity of using chemical pesticides. A team at the International Centre for Insect Physiology and Ecology (ICIPE) in Nairobi has identified and synthesized a specific locust pheromone, or chemical signal, that can be used against young locusts with devastating effect.

Phenylacetonitrile, or PAN for short, normally governs swarming behaviour in adult males who also use it to warn other males to leave them in peace while they mate. But, Hassanali found it has startlingly different results on juvenile wingless locusts, known as hoppers.

As with adult locusts, under the right conditions hoppers will abandon their normal individualistic behavior and form bands several kilometers long, causing similar kinds of devastations to crops as the adult swarms. ICIPE has found that even small doses of PAN cause the hoppers to resume sloitary habits, disorienting them, causing them to lose their voracious appetitite and to fall prey to predators. The low quantities of PAN required versus those of chemical fertilizers will represent a significant savings to poor countries and is expected to contribute to improved efficacy of this means of locust control.

Another promising new technology is Green Muscle ®, a bio-pesticide developed by the International Institute for Tropical Agriculture’s biological control centre in Cotonou, Benin, and
manufactured in South Africa. It contains spores of the naturally occurring fungus
/Metarhizium anisopliae/ var. acridum, which germinate on the skin of locusts and penetrate through their exoskeletons. The fungus then destroys the locust's tissues from the inside but has no effect on other life forms.

One drawback is that it takes days to kill the locusts. It is also relatively expensive and large-scale production would need to be organized. Another issues is its relatively short shelf-life in its normal ready-to-spray liquid form.

A solution would be to store the product in powder form and dilute it just before use. Tests at ICIPE have shown that, if used in combination with a small amount of PAN, only a quarter of the normal dose of Green Muscle ® is needed.

Along with better surveillance and tracking, it is expected that the new biological locust control agents will make a big difference to the cost and effectiveness of mankind's battle with the locust.