Azalea disease

Question: I have about12 azaleas in my backyard, age about 4 years, one just planted this spring. All of them a re losing an excessive amount of leaves and seems to have various issues. In the past I sprayed them with a Neem oil solution to get rid of the black spots and mildew. This year it seems to be something different altogether. If you need more detailed photos of the leaves/plants please let me know. Any suggestions for treatment are much appreciated.

responder: Louise RomanowEntomologistMaster Gardener VolunteerExtension MG Program, Wake County Replied July 23, 2023, 11:57 AM EDT
response: Looking at your pics, I see what appears to be leaf burn due probably to  the neem oil.  UNH, https://extension.unh.edu/blog/2020/01/what-should-neem-be-used-plants, states:Neem oil can also be used to manage some fungal disease issues, such as powdery mildew. It works by preventing the germination and penetration of fungal spores into leaf tissue. Neem won’t “cure” a plant that is already infected with a fungal disease, but it can help limit the spread of the disease to healthy tissue. Neem oil products are often labelled for a variety of crops such as herbs, vegetables, fruits, nuts and ornamental plants. Regardless of the type of plant being treated, neem oil can damage plants by burning their foliage. Do not use on recent transplants or otherwise stressed plants. Though plants must be completely covered with neem oil for the pesticide to be effective, it is a good idea to test the product on a small area first. If no toxicity symptoms occur in that spot, then the entire plant can be treated. When spraying an insecticidal oil or soap on a plant, it is always a good idea to do it when the plant is in shade.  If there is any likelihood of its damaging the plant, spray the plant thoroughly with water after you have allowed your initial application to dry. Note that neem oil is a prophylactic against mildew, i.e., a preventative, not a cure. Are you sure you had black spot?  If so, neem oil is not listed as a control measure.  Clemson, https://hgic.clemson.edu/factsheet/azalea-rhododendron-diseases/, lists a number of fungicides to use on azalea.  Again, these are prophylactic.  If you have black spot, which I do not see on the pics you included, follow their directions and remove diseased leaves, including those on the ground. There is some damage due to sucking insects (note the tiny white dots).  This is probably mite damage.  Look for webbing near the tips of damaged leaves. This is  done when they are preparing to move (by strands of webbing) to new plants.  Mites can be dislodged by a stream of water. Azalea lace bug also causes cell collapse, which appears as stippling on the leaves, but you should see specks of fecal material if this is the culprit.  Learn more at https://hgic.clemson.edu/factsheet/azalea-rhododendron-insect-pests/   Presently, I would not apply ANY pesticide or fertilizer to your plants.  They are stressed.  Keep them watered adequately and watch that new growth looks healthy.  If so, the plants will recover.  If you have whole stems that have died, clip them off.  Pruning stimulates new growth. A number of the links provide control recommendations, but avoid stressing your plants. Consider rinsing off insecticides to prevent leaf damage after the insecticide has dried.  They act as contact poisons on the insects unless you are using a systemic.

responder: The Question Asker Replied July 24, 2023, 4:53 PM EDT
response: Hi Louise, Thanks for the very helpful advice! I guess I have to be more careful with the treatments in the future. Best regardsKai Mahnke From: ask=<personal data hidden> <ask=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>>Date: Sunday, July 23, 2023 at 11:58To: Kai Mahnke <<personal data hidden>>Subject: Re: Azalea disease (#0111299)