Effects of restricting movement between root and canopy populations of woolly apple aphid

Summary

This study investigated whether restricting movement between spatially subdivided woolly apple aphid populations could reduce pest persistence in apple orchards. Field trials blocking upward movement via sticky barriers unexpectedly increased canopy aphid colonies, likely because barriers also excluded earwig predators. Greenhouse experiments found that sandy soils and mulches (wood chips or paper slurry) reduced root gall formation, suggesting soil management may offer partial protection against root-feeding populations.

UK applicability

Woolly apple aphid is present in UK apple orchards but is less prevalent than in other regions. The finding that soil amendments reduce root feeding may be relevant to UK growers, though the field results suggest sticky barriers are counterproductive due to exclusion of beneficial predators, a consideration applicable to UK integrated pest management.

Key measures

Aphid colony counts in tree canopies; root gall occurrence (indicative of root feeding); predator (earwig) abundance on trees; effects of sticky barriers on upward movement; effects of mulches and sand amendments on downward movement

Outcomes reported

The study evaluated whether restricting movement of woolly apple aphid between root and canopy populations reduces pest persistence and abundance. Field trials using sticky barriers and greenhouse experiments using soil amendments were conducted to assess the effectiveness of movement restriction on aphid colony counts and root gall formation.

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