Apple Orchard Dormant Sprays: Zinc Sulfate Not Recommended

Grower asks about dormant-season zinc sulfate application on apples.

Why Zinc Sulfate at Dormancy Is Ineffective

• Zinc sulfate = fungicide (primarily)
• Fungicides target foliar fungi—no leaves = no target
• Trunk moss/lichen control only minor benefit
• No insect control (overwintering pests need oil/insecticide)

Recommended Dormant/Delayed-Dormant Applications

1. Dormant Oil (Superior Oil)

• Targets: Scale, aphid eggs, mite eggs, overwintering insects
• Timing: Late winter, temps >40°F, before green tip
• Only if history of pest problems

2. Copper Fungicide (Fire Blight Prevention)

• Copper hydroxide, copper sulfate, Bordeaux mixture
• Timing: Late winter/early spring, before leaf emergence
• Critical: Late application causes fruit russeting
• Region/cultivar dependent—check local guidelines

3. State-Specific Spray Guides

Search "[Your State] apple spray schedule" for:

• Local pest/disease calendar
• Registered products and rates
• Growth-stage timing charts
• Resistance management strategies

Label Compliance Is Law

• Temperature restrictions
• Growth stage restrictions
• REI (re-entry interval), PHI (pre-harvest interval)
• Buffer zones, pollinator protection

Zinc has a role in apple nutrition—but as foliar chelate during growing season, not dormant sulfate spray.