Entomologist Professor Jerry Cross, speaking at last week's EMR members' day in Kent, said that GM technology may be necessary in helping growers to overcome the use of pesticides - which is "arguably the greatest and among the most important challenges faced by fruit growers".
Cross said that the public's suspicion of pesticides, combined with the incoming European Thematic Strategy for the Sustainable Use of Pesticides, will make it necessary for fruit growers to adopt new technologies in their commercial practice to reduce their dependence on these chemicals.
Currently, UK apple crops have on average more than 18 spray rounds, but technologies such as semi-chemical-based monitoring and control methods - developed for capsid bugs, blossom weevils, midges and raspberry beetle - can be integrated into commercial practice, said Cross.
Growers' dependence on Botrytis fungicides could be reduced by protected cropping coupled with better, lower-temperature cool chain marketing.
But for diseases such as scab on apple and mildew, Cross said that cisgenesis technology, a form of GM technology where only genes that are already present in varieties of the same plant are transferred, offers "very important opportunities" for growers.
Cross revealed that a cisgenic, scab-resistant Gala apple has been produced by the Swiss Federal Institute of Technology, in Zurich, as part of a federal-funded research project.
Cross said: "Varieties with durable disease resistance will be crucial [to UK growers].
"Public acceptance of the enormous benefits of this technology is necessary before it can be used. But this variety could occur at the national collection at Brogdale.
"GM does offer very important opportunities for reducing our dependence on pesticides."
Cross added that, in the short term, there is an agenda to greatly reduce - and, ideally, eliminate - the occurrence of pesticide residues. However, this is often a demoralising task for growers because legislators keep "moving the goalposts" - lowering the official reporting limits for various pesticides from 0.05mg/kg to 0.01mg/kg.
Results from different accredited laboratories can also vary up to tenfold due to sample-taking, said Cross. He added that the problems these factors cause are illustrated by the history of residues on apples experienced by Worldwide Fruit.
He said the producer organisation has achieved a fivefold reduction in the frequency of occurrence residues above 0.05mg/kg between 2006 and 2008.
But the percentage of samples with residues above the official reporting limits has risen from 23 per cent in 2006 to 78 per cent in 2008.
This, said Cross, is because the lowering of the reporting limit of boscalid (contained in Bellis and Signum) and other active ingredients from 0.05mg/kg to 0.01 mg/kg in 2008 "made elimination of residues much more difficult".
But Cross added that while the task of reducing residue levels is not being made easy, "it is not time to give up".
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