As bloom wraps up for many apple growers, the focus now shifts to managing shoot blight. With recent reports of shoot infections, I’m resharing key management tips from an earlier newsletter article to help review the fundamentals of shoot blight control.

The original article can be found here but below are some summary points regarding shoot blight management.

Fire blight shoot infections are a major concern during the growing season. Two key tools for suppression—Apogee/Kudos and Actigard—can significantly reduce shoot susceptibility when used alone or together.

Apogee/Kudos (Prohexadione-Calcium)

• A plant growth regulator that reduces shoot elongation by inhibiting gibberellic acid.
• Leads to shorter, thicker shoots with more lignified tissue, making it harder for Erwinia amylovora to invade.
• Timing: Apply when shoots are 1–3 inches long, usually between pink bud and petal fall.
• Takes 10–14 days for growth regulation to take effect.
• One application may suffice in moderate-risk blocks; repeat every 2–4 weeks in vigorous or high-risk trees.
• Does not kill the bacteria, but limits infection by hardening shoot tissue.
• A Section 2(ee) recommendation allows the first application from pink to 1–3″ shoot growth (valid through Dec 31, 2025).
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Actigard (Acibenzolar-S-Methyl)

• A systemic acquired resistance inducer—functions like a plant vaccine.
• Activates internal plant defenses.
• Most effective when applied preventatively; offers several weeks of protection.
• Works well alone, but even better when combined with Apogee.

Tank Mix: Apogee + Actigard

• Apply both at 1 oz/A as a tank mix for high-risk orchards.
• Provides a synergistic effect—Actigard primes the immune system while Apogee toughens shoot tissue.
• Field trials show 60–80% reduction in shoot blight incidence—more effective than using either product alone.
• Cost may be a limiting factor, so consider using solo Apogee programs for lower-risk or lower-vigor blocks.

Organic orchards

• Cueva (soluble copper) can be used in bloom to target shoot blight:
  • Effective but can cause russeting—apply during dry weather and avoid on sensitive cultivars.
  • Best reserved for non-bearing blocks or low-risk varieties.

• Hydrogen peroxide products (e.g., Oxidate 2.0/5.0):
  • Offer quick surface sanitation but no residual activity.
  • Use as pre-bloom sprays, especially if inoculum was present last season.

• Products like LifeGard and Regalia can be applied starting pre-bloom:
  • These stimulate plant immune responses and are most effective when integrated with biopesticides during bloom.

 

This article was posted in Apples, Disease and tagged Apples, disease, Fire Blight, Leslie Holland, shoot blight.