Delegates updated on fruit pest research work

The BIFGA Technical Day heard of a number of findings, not all successful, from ongoing and recently completed tree fruit research projects funded by levy body AHDB Horticulture.

Rhynchites: damage from apple fruit pest is on the rise - image: Christophe Quintin
Rhynchites: damage from apple fruit pest is on the rise - image: Christophe Quintin

East Malling Research entomologist Dr Michelle Fountain explained that developing a semiochemical monitoring trap for the apple fruit Rhynchites weevil has proved an elusive task. "There is little literature about Rhynchites but damage from it is increasing year on year, maybe due to tighter regulation of insecticides," she said.

During the project TF 209, which concluded last year, Fountain and a colleague set lures of both male and female populations in East Malling orchards but failed to detect any intra-species attraction. In the lab, isolating compounds emitted by captive weevils also failed to elicit a response when passed over the weevils' antennae.

Meanwhile, earwigs are now seen as an ally of the orchard grower, if not the soft-fruit grower, because they are effective predators of woolly apple aphids in particular, said Fountain. Another AHDB project, TF 220, has sought to ascertain the impact of modern insecticides on them, which may explain their highly variable distribution.

Under the project, which has now been extended, two commercial orchards with very different earwig levels were each divided into "standard" and "earwig-compatible" spray regimes. "We found a number of sub-lethal effects that could still affect populations over time," said Fountain. But she added: "If you already have lots, you may still be able to spray with 'unfriendly' pesticides."

Mating disruption of tortrix moth and codling moth, being developed within the wider TF 223 project to improve integrated pest and disease management in tree fruit, "could benefit earwigs, as with fewer harmful sprays they could provide control of other pests", she suggested.

AHDB fruit research and knowledge exchange manager Andrew Tinsley added that project TF 204 on timing of spraying against codling moth, which concluded last year, found that the standard spray threshold of five moths per trap per week for two weeks is too high for the crucial second generation later in the season, when three moths should now be considered the threshold. "You should continue to monitor for codling moths through the season," he added. "You can't just spray again and again with Chlorpyrifos."

Ongoing project TF 216 to evaluate products for control of the fungus Neonectria ditissima, the cause of canker on apples, has revealed two promising products, so far identified only by codes, that "are likely to be approved in the next year or two", he said.

Meanwhile, the rise of protected cherry growing has benefited the spider mite (Tetranychus urticae), which "loves protected conditions", said Tinsley. The ongoing project TF 219 is assessing the efficacy of the predatory mite Amblyseius andersoni, sold commercially in sachet form as Gemini.

"You don't need many of the sachets - just one per five trees", he pointed out. "But if there's no pest, you are wasting your time. You have to keep crop walking and if you see any hotspots, add more there."

Tinsley added that growers have welcomed the "little and often" way that AHDB has provided information on dealing with the recently arrived pest spotted-wing drosophila, including through social media, and said this would be extended as a means of giving growers timely information on other topics.

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