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Scientists find out a pheromone of the crop pest Moroccan locust

Scientists at the CSIC and at the Centro de Investigación y Tecnología Agroalimentaria, in Zaragoza, have identified a pheromone component of the Moroccan locust Dociostaurus maroccanus, a harmful crop pest. They are conducting field trials in order to develop a method to control this plague based on this pheromone

 

A female (the biggest one) and two males of Dociostaurus maroccanus. Dociostaurus maroccanus, commonly known as the Moroccan locust, causes serious damages to all kind of crops. Despite its name, it is a Mediterranean species which can be found across South Europe, North Africa and the Middle East.

Scientists at the Instituto de Química Avanzada de Cataluña (IQAC), in Barcelona, and at the Centro de Investigación y Tecnología Agroalimentaria, in Zaragoza, have identified a compound, called phytal, which is used by D. maroccanus males to attract females, possibly for reproduction purposes, but which also attract males. The study, recently published in the journal ChemBioChem, has been led by the CSIC scientists Angel Guerrero and Carmen Quero.

“Although we are not completely confident that phytal is a sex pheromone, we have shown in the laboratory that the pheromone is emitted by the legs and wings of adult males, and it is specific and effective for attracting females as well as males”, explains Angel Guerrero, Research Professor of CSIC and the leader of the Ecological Chemistry Unit of IQAC. The scientists have synthesized the two isomers of this compound, with the aim of study its activity and possible use to control the pest.

Aragón, Andalucía, Castilla La Mancha, Castilla León, Murcia and Extremadura are the Spanish areas more recently affected by Dociostaurus attacks. In the past there have been devastating outbreaks in Morocco, Iran, Afghanistan and other republics of the former URSS.  

The locust has no preference for any crop. It is a voracious insect and, as such, it feeds on fruits, leaves, barks, cereals and seeds. It can grow in fields with no vegetation at all. When new crops appear nearby, its population may grow exponentially.
 
The big plagues usually last 2-3 years, after which the population dramatically decreases to start growing again. This situation happens over and over again along the years. According to the Spanish Ministry of Agriculture and Fisheries, in Spain more than 160.000 hectares were treated annually between 2004 and 2007, with a cost around 2 million Euros, to fight against locust plagues, mostly Dociostaurus. In addition to the economic losses, the insecticides used against this plague are not specific and can harm other beneficial insects, such as bees and birds.

As Carmen Quero, CSIC scientist at the Ecological Chemistry Unit, explains: “The mechanism of action of insecticides can be by ingestion, contact or breathing through the cuticle. Dociostaurus is a very strong insect, big (adults are between 2 and 3,8 centimetres) and protected with a hard cuticle. To fight against it high doses of insecticide are required”.

The pheromone isolated by the scientists opens the possibility of developing a biological control method, more specific and less contaminant

One of these insecticides is malathion, which had been successfully used for controlling the pest until 2008, when it was prohibited for its risks for human health and the ecosystems. Another insecticide is diflubenzuron, more selective and less toxic than malathion. However, one of its metabolites is likely a human carcinogen, according to the U.S. Environmental Protection Agency.

The pheromone isolated by the scientists opens the possibility of developing a biological control method, more specific and less contaminant. Insect pheromones are highly specific molecules that regulate many aspects of insect behaviour, especially sexual attraction, mating and aggregation. Currently, the scientists are designing a device for trapping the insect while conducting field tests with the molecule. “It is not easy”, the scientists say, “It is necessary to know the behaviour of the insect, to develop a suitable trap and emitter, to determine the correct amount of pheromone needed, to learn how this molecule works in the open field, etc.”       

“It is the first time that a pheromone from an endemic locust is identified in Spain. Although there have been some previous works on pheromones of other species of locusts, in Spain we had no previous experience on these insects and very little was known about the chemical communication of the Moroccan locust. Therefore, we had to start from the very beginning”, the scientists explain.   

The scientific team of the Ecological Chemistry Unit is pioneer in Spain in the development of environmentally friendly and specific strategies for pest control. At the beginning of the 80’s they characterized the pheromone of the pine processionary moth, which has been used since then for the control of this pest throughout Spain. Currently, the team is working on other pests, such as Coroebus undatus, a cork oak borer; Tuta absoluta, a devastating pest of tomatoes; and Grapholita molesta, a pest of stone fruit crops, mostly peaches.

Contact:

Angel Guerrero [This email address is being protected from spambots. You need JavaScript enabled to view it.]
Química Biològica i Modelització Molecular, IQAC-CSIC
Jordi Girona, 18-26,
08034 Barcelona
Tel. (34) 93 400 61 71