At a Glance
- Set your green tip date in the Apple Scab model (Gala or McIntosh are usually first indicators).
- Infections can occur from green tip through harvest; monitor for infection conditions.
- If you had scab last year, keep trees protected from green tip to half-inch green.
- During the primary scab period (green tip to end of June), use protectants every 7–14 days and back up with eradicants as needed.
- For resistance management, consider tank mixes (protectant and eradicant).
- Reduce risk: avoid overhead sprinklers in problem blocks; treat leaf litter in fall (5% urea, dolomitic lime, chop/shred).
Set Your Green Tip Date
Scab season begins when buds reach green tip. Go into the Apple Scab model and set the green tip date for your orchard as soon as it occurs. If you have Gala or McIntosh, use those blocks to set the date because they usually show green tip first.
Monitor Infection Conditions
Scab infections can be initiated from green tip through to harvest. Once buds reach green tip, begin monitoring weather for infection conditions.
In the BC DAS scab model, the tables and graphs show hours of rainfall, dew, or moisture and air temperature. Check the graph for scab infection periods — a colour change appears in the cumulative wetness graph from yellow (rain event) to red (scab infection).
Protection Strategy
If you had a scab problem last year, keep trees protected by applying scab protection products from green tip to half-inch green. Use the Protectants list in the DAS Spray Guide . During the primary scab infection period (green tip to end of June), follow a protectant program on 7–14 day intervals. It is recommended that a protectant program be backed up with eradicant sprays, as necessary, to maintain thorough coverage during the primary period. Use the Eradicants list in the DAS Spray Guide . For pesticide resistance management, growers may consider tank mixes with a protectant and an eradicant.
Reduce Orchard Risk
Avoid the use of overhead sprinklers in orchards that have had scab in the last couple of seasons. In the fall, treat leaf litter to increase decomposition and reduce spore carryover:
- Apply a 5% urea solution on the tree or on the ground after leaf fall.
- Apply dolomitic lime to the ground to help break down leaves.
- Chop or shred leaf litter prior to snowfall.