Good Fruit Grower

November 2013

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New Equipment & Technology photos courtesy of oxitec Pests modified with lethal genes Mediterranean fruit fly and spotted wing drosophila are two insect pests Oxitec is planning to attack using RIDL. Mediterranean fruit flies mate. Lethal genes put to work can decimate insect pest populations. by Richard Lehnert A British biotechnology company is developing a novel new way to control insect pests. Called RIDL, which stands for Release of Insects with Dominant Lethality, it works somewhat like sterile insect releases. Instead of using radiation to create sterile male insects that mate ineffectively with females, lethal genes inserted into a strain of insects kill the offspring of any females that the altered males mate with. The company, Oxitec, located in Oxford, England, has applied to authorities in Spain for permission to evaluate its genetically modified olive fly, which could be used to suppress one of Europe's most damaging insect pests. It has also applied to Brazil to carry out trials on its genetically modified Mediterranean fruit fly. If approved by Spain, the study would be the first outdoor trial of a genetically modified insect in the European Union, according to Oxitec. The company is already applying the RIDL technique in Brazil to control mosquitoes that carry dengue fever, and is working on agricultural applications for control of pink bollworm, Mediterranean fruit fly, Mexican fruit fly, spotted wing drosophila, diamondback moth, and tomato leafminer. The technology could be used against other pests that affect fruit crops—codling moth, oriental fruit moth, and many others. "We are applying this approach in a number of insect pests besides the olive fly and are at various stages of developing the technology in other species," said Michael Conway, a spokesperson for Oxitec, in an e-mail exchange with Good Fruit Grower. Basic strategy "The basis of the strategy in all of these insects is that we modify the insects with a gene that is lethal to their offspring once outside the laboratory," Conway said. "The gene can be lethal to both male and female insects or can be specific to females; either way, the effect is essentially the same." The lethal gene, called tTA, makes the insect dependant on tetracycline to live. So during rearing, the insects are given tetracycline. After being released and mating, they die, as do all of their offspring. Modified males, after release, track down and mate with wild female insects. So how do insects get these lethal genes? 18 NOVEMBER 2013 Good Fruit Grower

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