Combining sugar diversion with flower-strip management weakens ant protection of aphids in apple orchards

Protection provided by ants to honeydew-producing insects can limit biological control by reducing predator access to pest colonies. Providing artificial sugar sources away from aphid colonies has been proposed as a way to redirect ant foraging from honeydew to alternative carbohydrate resources, but its effectiveness may depend on habitat context and the timing of sugar provisioning. We tested whether sugar diversion weakens ant-mediated protection of the rosy apple aphid, Dysaphis plantaginea , and whether its effect depends on provisioning timing and flower-strip management in apple orchards. Over two growing seasons with contrasting aphid pressure, we manipulated sugar provisioning timing, early, late or none, and flower-strip management, comparing intact and mown flower strips. We followed 5,187 individually identified aphid colonies through 13,303 active colony observations, monitoring aphid colony dynamics, ant attendance, predator abundance, predator access and colony survival. Sugar diversion reduced the probability and intensity of ant attendance, including relative ant attendance after accounting for aphid abundance. Predator abundance was affected by sugar-treatment timing and was highest when sugar diversion was combined with intact flower strips. Predator abundance was lower on ant-attended colonies than on colonies without attending ants, indicating that ant attendance constrained predator access to aphid colonies. Sugar diversion also shifted aphid colony size structure, with sugar-treated plots containing a higher proportion of smaller colonies at peak aphid activity. Colony-survival responses were more variable, but the clearest increase in disappearance risk occurred under late diversion in intact flower-strip plots. Combining sugar diversion with flower-strip management weakened ant-mediated aphid protection and improved conditions for conservation biological control in orchards. Rather than suppressing ants directly, this approach manipulates ant foraging behaviour to reduce interference with natural enemies and may provide a complementary tactic for managing ant-protected aphids in perennial fruit systems.