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Bio-pesticide may number days of the locust
In Arabic, the word for locust translates as "teeth of the wind," an appropriate phrase for an insect that destroys virtually everything in its path.
Swarms of locusts have long plagued farmers around the world. Because the pests travel great distances and devour crops in unpredictable cycles every 10 to 20 years, farmers have had little defense when locusts strike.
But the voracious pests face a new line of attack.
Scientists revealed today that they have successfully developed and applied a natural, ecologically safe bio-pesticide for locusts and grasshoppers.
Unlike chemical pesticides that are usually applied to combat locusts, the microbial bio-pesticide developed by researchers from the Nigeria-based International Institute of Tropical Agriculture consists of living organisms specific to the host organism.
Synthetic locust sprays are not as selective as the bio-pesticide, explained entomologist and project leader Jürgen Langewald. "Chemical pesticides kill many other organisms that might be beneficial to agriculture."
According to IITA, persistent spraying of chemical pesticides in Africa has contributed to large decreases in the number of migratory birds that make it to Europe.
Sprayed in its live form, the microbial pesticide, dubbed "Green Muscle" by scientists, can protect crops longer than chemical pesticides. It also poses fewer health problems to communities.
"This is important especially in developing countries, because people do not take precautions like they should," Langewald said. "Many people don't wear masks or protective clothing as required by the chemical industry. Leftover barrels of spray can also contaminate ground water."
Locusts and grasshoppers belong to the same family, Acrididae. The only difference between the two insects is that locusts have two behavioral states. "At low populations they behave like normal grasshoppers; they hop around and are happy on their own," Langewald explained. "As the population densities become higher, they produce a hormone which makes them change their color and behavior. Then they start to group (and prepare for their attack). It is a critical situation in locust control."
When a spore of the live fungus lands on an insect, it bores a hole in the insect's exoskeleton and invades the tissue of the insect's entire body, Langewald said. "It ingests the locust from the inside out, if you like."
The dead, reddish-colored insect takes on the appearance of an "empty soup can." But the fungus perseveres, forming new spores on the carcass. Because locusts and grasshoppers often prey on deceased members of their own kind, the spores can attack new insects.
"This reduces the amount of the microbial pesticide that needs to be sprayed," Langewald said. This means lower costs for farmers.
While the microbial pesticide can be applied for about $10 per hectare, about the same price as chemical pesticide, it stays active in the environment for a much longer time and can be applied once a season.
Requiring several applications per season, chemical pesticides create an "empty ecological niche," inviting more locusts to take their place.
The price of a 1986 locust invasion in West Africa was about $300 million and consumed the amount of vegetation equivalent to the daily food need of about 200 million people, according to pest control experts.
The microbial spray can be used for entire locust swarms or pesky grasshoppers that appear on a regular basis. Scientists are also proposing to use the bio-pesticide to attack locusts in their breeding grounds.
"The eggs can only develop when it rains," Langewald said. "If you see rain for two or three consecutive years, it is likely that they will develop enormous population densities." As a preventive strategy, locust-breeding areas, which exist primarily in the desert, could be treated each year.
The search for an environmentally friendly alternative to synthetic pesticide began in 1989 at the Center for Agriculture and Biosciences International, in Britian. IITA developed Green Muscle through an international research consortium called the Biological Control of Locusts and Grasshoppers. Large-scale applications of the bio-pesticide began in 1996 near Lake Chad in Africa.
Copyright 2000, Environmental News Network, All Rights Reserved
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