Preharvest Fungicide Tips to Prevent Apple Rots

By Blake Jackson

This season’s persistent rainfall since May 1 has significantly heightened the risk of fruit rots in apple orchards. Weather records from Biglerville, Pennsylvania, show a stark increase in rainfall from April 1 to July 31: 13.27 inches in 2023, 13.64 inches in 2024, and 21.06 inches so far in 2025 and the season isn’t over yet.

Even if drier conditions prevail in the coming weeks, ideal rot conditions have already led to widespread fungal infections, increasing the likelihood of latent infections in fruit still on trees.

These hidden infections can be especially problematic for apples destined for long-term cold storage. To reduce postharvest losses, growers are urged to take proactive steps now.

Key Preharvest Reminders:

• Do not extend the interval between your last fungicide spray and harvest particularly for fruit intended for storage. Some varieties may spend 2-3 months or longer in cold storage.
• Rot management begins in the orchard. Research shows Alternaria and Bull’s eye rots, two major storage diseases, start before harvest.

Fungicide Strategies:

While captan is effective against bitter rot, it is prone to wash-off during heavy rains. Consider using more persistent fungicides as your final spray:

• Merivon (FRAC 7 + 11; 0-day PHI)
• Luna Sensation (FRAC 7 + 11; 14-day PHI)
• Flint Extra (FRAC 11; 14-day PHI)

For organic growers, sulfur, Oso (6.5 fl oz/A), and biologicals like Serenade or Double Nickel offer short-term control, especially for fruit that won’t be stored long.

Postharvest Rot Risks and Control:

Latent rot infections can become entry points for blue mold during storage, caused by Penicillium spp., which produce the regulated mycotoxin patulin. To limit contamination, apply preharvest or postharvest fungicides such as:

• Scholar (FRAC 12)
• Penbotec (FRAC 9)
• Academy (FRAC 3 + 12)
• Mertect (FRAC 1, but best used in combination due to resistance)

Additional Best Practices:

• Remove rotting fruit during harvest to reduce canopy infection.
• Harvest at optimal maturity.
• Handle fruit gently to avoid bruising.
• Use clean bins and minimize debris.
• Keep harvested fruit shaded and cool.
• Deliver fruit promptly to packing facilities.

Photo Credit: istock-rixipix