Azalea has Crown Rot & Treatment


10/25/2020 – The azalea on the east side of the gap between the backyard and the barnyard has had limbs dying. Diagnosis of it having Crown rot or wilt, Phytophthora, and the treatment was based on the advice from the LSU Ag Center; “Scraping away the bark with a knife revealed discolored wood under the bark that appears chocolate brown.

11/2/2020 – Poured a quart of hydrogen peroxide in 2 gallons of water around the stump and into the stump.

11/4/2020 – Used the hack saw to remove the dead stalks where most were 1.5 – 2″ in diameter. When the bark was skimmed off a chocolate brown layer was easily visible on top of the white wood below. Sprayed Mancozeb on the cut stalk nubs and the normal stalks on the same plant. Also sprayed the trunks of the adjacent plant to the east. As the first hydrogen peroxide drench was at 7:1 and the recommendation is 3:1, poured 2 gallons of a 3:1 solution around the base from the center out about 18″.

8/11/2021 – Despite more treatments with mancozeb the plant has died and today was pulled out. The hole was drenched with water + hydrogen peroxide at 3:1 and filled with topsoil from Dawes Turf Farm. The adjacent azalea was sprayed with mancozeb.

From LSU Ag Center’s “Problems With Old Azaleas”.

  • Dieback is a disease of azaleas caused by the fungus Phomopsis. Typically, dying branches (stem dieback) begin to appear on an otherwise healthy plant. The leaves die and remain attached to the plant. Usually a single branch or a few branches on an established plant are affected. Scraping away the bark with a knife reveals discolored wood under the bark that appears chocolate brown.
  • Prune infected branches well below all discolored wood and dispose of dead plant material. Clean pruning tools between cuts with a diluted solution of household bleach (1 part bleach to 9 parts water) or 70% rubbing alcohol. Fungicide sprays containing either thiophanate-methyl or mancozeb can be used after pruning to reduce the chance of additional symptoms.

From Phytophthora Root Rot Symptoms, Treatment, and Prevention.

Hydrogen Peroxide — The application of a 3% solution of household hydrogen peroxide to your soil is effective in killing pathogens and diseases like Phytophthora. Apply a mixture of 1 part peroxide to 3 parts water and allow it to penetrate the soil before regular watering resumes.

Links to Useful Info

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