Rainfall Spurs Fire Blight Risk in Young Apple Trees

By Blake Jackson

Apple growers are facing continued fire blight infections due to multiple infection events from mid-April through early May. While control efforts have helped, they’ve not been entirely effective.

Continued rainfall has encouraged new tree growth, which remains vulnerable to the disease, prompting a need for effective and timely management strategies.

A triage approach to pruning is advised. Focus first on young orchards (3-8 years old) with minimal strikes, followed by those with numerous infections.

Older orchards with few infections come next, while severely affected orchards where most trees would require removal should often be left alone, as aggressive pruning can promote new susceptible growth.

Key pruning tips include avoiding cuts during wet weather, targeting early infections, and using the “ugly stub” method cutting 6-12 inches below visible symptoms.

Burn removed branches if possible or allow them to dry in row middles and mulch later. Tool sterilization is often ineffective since bacteria can move ahead of visible symptoms.

The “Actigard Paint” method can also help apply a concentrated Actigard solution directly to pruning wounds and nearby trunk areas, avoiding foliage to prevent damage.

Prohexadione calcium (Apogee or Kudos) is another option to curb growth and limit infection spread. For enhanced control, it can be combined with Actigard in multiple applications.

In older trees, canker blight a renewed bacterial activity from old cankers is a hidden but damaging threat. It often mimics shoot blight but starts at the base of shoots and spreads internally. This form is not manageable with pruning or topical sprays and must be suppressed early in the season with Prohexadione calcium.

Trauma blight from wind or hail poses an additional risk. Damaged tissue invites infection, so using antibiotics like streptomycin within 24 hours of storms is recommended.

Bitter rot is also a major concern this season due to heat and moisture. Preventive fungicide sprays before rain events are key.

Effective options include captan or ziram, tank-mixed with FRAC 7, 11, or 29 fungicides. Adding potassium phosphites or Regalia has shown added protection.

Organic growers face limited options, with sulfur and biopesticides offering modest results. Research continues to expand available tools for all growers.

Photo Credit: gettyimages-richard-7