Student - March 12, 2009


Rodents cause massive global harvest losses. If they are properly dealt with, 280 million more people can be fed, which is one third of the number currently suffering from hunger. This is the claim made by Wageningen pest management expert Bastiaan Meerburg and two fellow scientists in the April issue of Pest Management Science.

Hanging on: a harvest mouse, <em>Micromys minutus</em>, in the wheat.
Together with Grant Singleton of the research institute IRRI and Herwig Leirs of the University of Antwerp, Meerburg calculated harvest losses caused by rats and mice in developing countries. In Asia an average of five to ten percent of the rice production is eaten by rodents. In a country like Indonesia, with a figure of 17%, rats and mice are even the biggest cause of losses for farmers.

The situation is no better in Africa. The researchers present figures from Tanzania, where rodents consume fifteen percent of the maize harvest, and Kenya, where twenty percent is lost to them. In Latin America, harvest losses vary widely from five to as much as nineteen percent.
The researchers also mention the role of rodents in spreading disease. For instance, the leptospira bacterium, spread by rodents, causes a lot of illness and many deaths in North-East Thailand and the Philippines. Although there is little data about this, the researchers guess that many working days are lost to this disease among rice and grain growers.

Meerburg and his colleagues believe that effective rodent control could reduce global harvest losses by five percent, bringing significantly more food onto the local market. In Asia, 54 million extra tons of grain would be available, enough to feed 217 million people. Pest control in Africa and Latin America would provide food for 22 and 31 million people, respectively.

To control rodents, Meerburg thinks in the first place in terms of ecological management, the form of which can vary per region. Farmers first have to identify the species to be controlled and then make use of the ecology of that species in order to limit the damage it does, he explains. For example, in the fields rodents can be controlled by growing a crop they prefer next to the grain field. ‘Like that you move them away’, says Meerburg. There have also been successful trials with screens around a rice field. ‘That is only possible in countries where labour is cheap’, he says. Using natural enemies like dogs is another tried and trusted method.

A lot can be done to improve grain storage too. ‘You should seal the stores well, and fill up any holes. It also helps to remove bushes from around the buildings – mice and rats don’t like open terrain.’ Meerburg does not favour the use of more poison. ‘That carries environmental risks.’