Potential new weapon against crop pests discovered

The research team discovered that some African armyworms carry a small bacterium called Wolbachia which makes them more vulnerable to a natural virus which can be used as a biopesticide.

The African armyworm is a devastating caterpillar pest which feeds on cereal crops, including maize, wheat, millet and rice. Up to 500,000 caterpillars can sometimes attack a single hectare and totally destroy a crop. They are a major threat to food security in Africa, where chemical pesticides are too expensive for most farmers.

David Grzywacz, Entomologist & Virologist at the University of Greenwich, says: "The mass release of insects infected Wolbachia couldturn out to be an important new tool in the fight to control some insect crop pests. It may prove particularly useful for those that are difficult to control with chemical pesticides."

Researchers at the University of Greenwich, Lancaster University and a Tanzanian company called EcoAgriConsult have been investigating safe, affordable control measures to tackle the caterpillars.

They have been researching into SpexNPV, a virus that naturally infects and kills the African armyworm, and which shows great promise for use as a biopesticide in Africa. Not only can it be produced cheaply and locally, but it infects only armyworm caterpillars, leaving beneficial insects, livestock and humans completely unharmed.

The University of Greenwich researchers found that, in common with many insects, some African armyworms carry a small bacterium, which can protect mosquitoes and some other insects from infection by viruses. The research team wondered if this bacterium has a similarly protective effect on African armyworms, potentially hampering the effectiveness of the biopesticide they were investigating.

However they discovered that the opposite was true. Armyworm carrying the bacterium were between six and 14 times more susceptible to SpexNPV and more died of infection.

The three year research project was funded by UK's Department for International Development and the Biotechnology and Biological Sciences Research Council.