A hanging basket style device is at the heart of a plan byresearchers at the University of Warwick to harness the sex drive of amajor pest of fruit orchards as a weapon to spread a virus to kill thatvery same pest. The device allows growers to selectively target thepest with a virus that kills its larvae without killing otherbeneficial insects.
The researchers at Warwick HRI, thehorticultural research arm of the University of Warwick, have devised ahanging basket style dispenser full of a virus known to kill the larvaeof codling moth. The dispenser is designed to protect the virus fromthe elements and also includes a strong source of codling mothpheromone. The pheromone draws in the moth hoping for a sexualencounter and the insect leaves frustrated but covered in the viruswhich it then passes on to other moths when it does manage to have anactual encounter with another real moth. This results in directcontamination of eggs laid by the pest or contamination of the sitewhere the moth lays its eggs. The larvae are killed after eating thevirus on the egg or plant surface. This brings two key benefits tofruit growers:
An end to spraying - Normally Growers wishing touse this form of virus warfare have to spray almost every element of anorchard to ensure the moths come into contact with virus. This iswasteful both of time and resources. By this method the moth themselvesspread the virus in a very targeted way to other moths and preventsloss of populations of other beneficial insects such as the red spidermite which would occur if growers used pesticides.
Extended viruslife - The virus does not fare well in direct sunlight. Growers whocurrently spray the virus find it quickly becomes ineffective and ithas to re-sprayed several times in order to control the pests. Byplacing the virus in dispensers with a cover that shields the virussupply from direct sunlight one application of virus could serve for anextended period and remove the need for constant reapplication
Inthis Defra funded project the researchers have already tested theeffect of a single dispenser which alone infected 5% of all the mothsfound over a 1 hectare site. That early test helped them maximize thebest virus formulation, and the most efficient dispenser design thatmaximised access for the moths while protecting the virus from sunlightand other elements, and the best form of pheromone lure. That test alsohelped them choose between a liquid and powder based mix for the virus- the liquid was found to be best. The University of Warwickresearchers are now working with colleagues from East Malling Researchon a larger scale 12 hectare trial of the dispenser in a largecommercial apple orchard in Worcestershire. An array of 25 dispensersper hectare have been erected over 3 separated orchard plots of onehectare within an even larger orchard. The codling moth control withinthese three 1 hectare plots will be compared to similar sized orchardplots with dispensers without virus, or no treatment or sprayed with acommercial virus spray at the same virus dose.
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