Nursery Notes: Fireblight has been bad this year
The big concern for many has been fireblight, mostly on crabapple, but a few serviceberry were hit. Turns out, it has been a bad year for fireblight.
The only thing that can be done now, is prune it out and hope for regrowth. Make the cuts 6 to 10 inches below the affected part. Disinfect the pruners between every cut to ensure not spreading it all over again in case the cut is not made low enough. (The infection will be below the visual symptoms.)
Branches can be cut back on plants older than 2 to 3 years, but the pathogen may travel down short branches into the main trunk of first year plants. There is no way to make that plant salable.
The crabapple in front of McMinnville Electric at the corner of Morford and Chancery has a severe case of fireblight. The branches appear to have a foot of new growth killed. If left alone, the branches will provide the spores for next year, assuming the environmental conditions are favorable.
The pruning is a fairly simple task, requiring a sharp pair of hand pruners, time and plenty to drink. Disinfecting between each cut complicates the task. The big problem is convenience and speed. It is difficult to carry a bucket of bleach to dip into. Alcohol wipes can be used. Most spray bottles are too large and too clumsy. A plastic milk or bleach bottle is usually used, with a hole cut in the side to allow the pruners to be dipped into. There is a handle to carry by hand or strapped to belt.
———
Disinfecting pruners: Recent research suggests using Lysol or household bleach diluted 1 to 4 with water, not 1 to 10 as formerly recommended. Lysol is just as effective, with less corrosion to metal and safer to clothing. Best results were obtained by soaking the tools for at least one minute, as opposed to dipping. I have not personally had anyone let me know that the disease started up again after correct pruning and dipping.
But there is a reason to use a more concentrated disinfectant. “The higher the concentration, the shorter the ‘soak time’. Personally, I favor the quaternary ammonium disinfectants such as GreenShield, Consan, Physan etc. I would mix as directed in a spray bottle and spray my pruners frequently while pruning.”- Dr. Alan S. Windham, UT Ext Plant Pathologist.
Finding a convenient, small spray bottle to use can make the task go much faster. I shopped several stores and never found my ideal. It must be user friendly.
Now is a good time to consider growing some of the more resistant cultivars. I can fax or e-mail a list. Thank goodness all years are not good for fireblight.
Also consider not fertilizing these crops til May, hopefully reducing the amount of tender, succulent growth that will be killed by fireblight. Fertilization makes fireblight kill more growth.
———
Avoid pathogens from entering pruning wounds – Spray Cleary’s 3336 ASAP after major limbing up in order to prevent some of the canker diseases. This is a good idea, but may not be essential. We have observed infections over the years that appeared to have entered though fresh wounds created by normal pruning, limbing up. The rate is 20 fl oz/100 gal of the flowable formulation. Any labeled thiophanate methyl product will be fine.
———
According to the Task Calendar, it is time to apply Terraclor or Contrast to prevent southern blight on first year apple and crabapple plants, and possibly small, second year plants. The bark on older plants is thick enough to resist an attack. The fact sheet was provided at the recent MTNA meeting. I can fax or e-mail. It contains the rates and procedure.