BC-DAS system users should go into the Apple Scab model now to set the date of green tip for when it occurs in your orchard. Use Gala or McIntosh varieties to set the date if you have them, as these are usually the first varieties to show green tip.
Scab infections can be initiated from Green Tip through to harvest. As soon as buds reach green tip growers must begin to monitor the weather for infection conditions. The tables and graphs in the BC-DAS scab model will show the hours of rainfall/dew/moisture accumulated in the orchard and the air temperature. Please check the graph for scab infection periods – a colour change will be seen in the graph of cumulative wetness. The yellow bars (rain event) to RED (scab infection).
Growers with a scab problem last year should keep trees PROTECTED by applying scab protection products starting at green tip to half-inch green. Click on the list of Protectants in the DAS Spray Guide box.
Protectant programs are recommended on 7 to 14 day intervals during primary scab infection period (Green Tip to end of June). It is recommended that a protectant program be backed up with eradicant sprays, as necessary, to maintain thorough coverage during the primary scab infection period. Click on the list of Eradicants after infection in the DAS Spray Guide box.
For pesticide resistance management, growers may consider tank mixes with a protectant and eradicant.
Other tips for reducing potential scab infections in your orchard:
- Avoid the use of overhead sprinklers in orchards that have had scab in the last couple of seasons
- Treat leaf litter in the fall to increase decomposition and reduce the amount of spores carrying over (5% urea solution on tree or on ground once leaves have fallen; ground application of dolomitic lime to breakdown leaves; chopping or shredding of leaf litter prior to snowfall).