Integrating scab control methods with partial effects in apple orchards: the association of cultivar resistance, sanitation and reduced fungicide schedules
Abstract: To preserve the environment, consumer health and reduce the economic impacts of apple scab, it is crucial to improve disease control while reducing the number of treatments and the impact of fungicide spraying. To reach this goal, the planting of cultivars with partial resistance to the disease, associated with an integrated control strategy, may be an attractive alternative. However, to decrease the risks for growers, cultivars with a high partial resistance level are required, and several methods of control must be associated. The application of such a strategy must be simple and reliable. The thresholds for chemical spraying must be defined and validated, taking into account the cultivar resistance level and the sanitation practices applied. Since 2006, we have studied within an experimental orchard the association of the cultivar ‘Reine des Reinettes’ (which presents good partial resistance) with:i) A sanitation practice: reduction of leaf litter.ii) A chemical schedule: fungicide spraying only if a medium or high Mill’s risk is recorded or expected.The results obtained in 2006 and 2007 showed that, with only 5 to 6 sprayings per season (on average, twice as many sprays were applied in conventional orchards in the Loire Valley), scab control was efficient with less than 2% of scabbed fruits.