How Wisconsin Growers Can Reduce Fire Blight Damage Now

By Blake Jackson

As apple bloom season comes to an end across much of Wisconsin, growers are being encouraged to shift their attention toward managing fire blight shoot infections.

According to Leslie Holland, Assistant Professor and Extension Specialist at the University of Wisconsin-Madison, symptoms are already appearing in some orchards, and upcoming warm weather could speed up disease development.

Current blossom blight symptoms are largely linked to infections that occurred during bloom. While those infections cannot be reversed, growers can still take action to reduce disease spread and limit future shoot blight damage.

Regular orchard scouting is essential. Producers should inspect orchards weekly, especially blocks with susceptible varieties, young trees, or a history of fire blight.

Common signs include darkened flower clusters that remain attached, wilted shoot tips forming a “shepherd’s crook,” blackened leaves, water-soaked tissue, and bacterial ooze during humid conditions.

Where infections are limited, pruning can help slow disease movement. Infected shoots should be removed 8 to 12 inches below visible symptoms and cut material should be destroyed or removed from the orchard when possible. Extensive pruning should be avoided during hot, wet weather, which can increase bacterial spread.

Prohexadione-calcium products, marketed as Apogee and Kudos, remain valuable tools for managing shoot blight. These plant growth regulators reduce shoot growth and strengthen tissue, making trees less vulnerable to infection.

Applications are most effective when applied early and preventatively.

Actigard offers another option by stimulating the tree’s natural defense system. Because it works by activating plant immunity, it should also be applied before infection occurs.

Research has shown that combining Apogee or Kudos with Actigard can improve fire blight suppression by addressing both shoot susceptibility and plant defenses.

Organic growers may consider products such as soluble copper materials, LifeGard, Regalia, and OxiDate as part of an integrated disease management strategy.

Photo Credit: istock-rixipix