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A hanging basket style device is at the heart of a plan by researchers at the University of Warwick to harness the sex drive of a major pest of fruit orchards as a weapon to spread a virus to kill that very same pest. The device allows growers to selectively target the pest with a virus that kills its larvae without killing other beneficial insects.

The researchers at Warwick HRI, the horticultural research arm of the University of Warwick, have devised a hanging basket style dispenser full of a virus known to kill the larvae of codling moth. The dispenser is designed to protect the virus from the elements and also includes a strong source of codling moth pheromone. The pheromone draws in the moth hoping for a sexual encounter and the insect leaves frustrated but covered in the virus which it then passes on to other moths when it does manage to have an actual encounter with another real moth. This results in direct contamination of eggs laid by the pest or contamination of the site where the moth lays its eggs. The larvae are killed after eating the virus on the egg or plant surface. This brings two key benefits to fruit growers:

An end to spraying - Normally Growers wishing to use this form of virus warfare have to spray almost every element of an orchard to ensure the moths come into contact with virus. This is wasteful both of time and resources. By this method the moth themselves spread the virus in a very targeted way to other moths and prevents loss of populations of other beneficial insects such as the red spider mite which would occur if growers used pesticides.

Extended virus life - The virus does not fare well in direct sunlight. Growers who currently spray the virus find it quickly becomes ineffective and it has to re-sprayed several times in order to control the pests. By placing the virus in dispensers with a cover that shields the virus supply from direct sunlight one application of virus could serve for an extended period and remove the need for constant reapplication

In this Defra funded project the researchers have already tested the effect of a single dispenser which alone infected 5% of all the moths found over a 1 hectare site. That early test helped them maximize the best virus formulation, and the most efficient dispenser design that maximised access for the moths while protecting the virus from sunlight and other elements, and the best form of pheromone lure. That test also helped them choose between a liquid and powder based mix for the virus - the liquid was found to be best. The University of Warwick researchers are now working with colleagues from East Malling Research on a larger scale 12 hectare trial of the dispenser in a large commercial apple orchard in Worcestershire. An array of 25 dispensers per hectare have been erected over 3 separated orchard plots of one hectare within an even larger orchard. The codling moth control within these three 1 hectare plots will be compared to similar sized orchard plots with dispensers without virus, or no treatment or sprayed with a commercial virus spray at the same virus dose.

Source : University of Warwick

September 20, 2005 11:33 PMBiology

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