Rhododendron infestation

Question: What is ailing my rhodie? Is it treatable or will I need to replace it? It is in the southwest corner of my backyard. Gets morning and some early afternoon sun in the summer. Variety is Percy Wiseman.

responder: Sheryl Casteen Replied April 03, 2023, 2:52 PM EDT
response: Dear Renee, Looks like the plant is filled with mites and mold.  The stems around the buds and the buds look like mold and the leaves have spider mite damage.   Best options are to spray with Neem oil and then with a spray with bicarbonate soda in it.  Pure Neem oil should be purchased and mix according to directions with water.  Spray the entire plant both sides of the leaves and the stems and buds.  Pure neem oil can be found online.  It does gel, but putting the bottle in a warm bowl of water will return it to liquid.  More is not better, follow the instructions.  This is an organic spray but it will kill all insects.  Do not spray around pollinators.   The other is a bicarbonate spray often made with a mild soap to spray on the leaves.  Wait 10 days before spraying if you have sprayed with Neem oil.   Or you can use a sulfur spray, found at the store.  Look for organic, Safer, or OMRI labels.  Again wait 10 days between sprays.   These are different categories of sprays and they attack in different ways.  Neem  and sulfur sprays will kill molds (fungal growths) as well as insects.   Use gloves and safety glasses, spray when dry if at all possible and not windy.  Do not breathe in the sprays.  Even though they are organic (the ones mentioned above) you do not want to get it in your lungs. These are just basic, normal precautions. Here is a link to Oregon State publication on rhodies for your reveiw:  https://catalog.extension.oregonstate.edu/fs12/html Any further questions, please contact us again.   If you have other plants in the area, check them out as well.

responder: The Question Asker Replied April 06, 2023, 4:59 PM EDT
response: Great!  Just a couple of clarifying questions while we wait for the rain to stop:1. I have some RTU neem oil spray (Bonide Captain Jack's 0.9% Neem Oil).  Can I use that?    a. For the underside of the leaves can I soak a cloth and wipe it on?  Thinking it may be easier than turning each leaf over or spraying upside down.2. The bicarbonate spray: Bicarb of soda? Can I use an insecticidal soap as the spreader/sticker?3. Spraying schedule: Alternate neem oil and bicarb spray every 10 days? I have Nitrile gloves, N95 masks (don't we all, now?) and swim googles I use when spraying.4. I am unable to access the OSU article on Azalea and Rhododendron Care. I get this message: HTML version of publication is not available.  I have tried looking for it in the gardening index and I am not seeing it.I think that  is it!Thanks again for your help. Renee  On Monday, April 3, 2023 at 11:52:09 AM PDT, Ask Extension <<personal data hidden>> wrote:

responder: Sheryl Casteen Replied April 06, 2023, 5:50 PM EDT
response: Hi Renee, The trouble with Neem oil from other providers is the 99% other ingredients.  What are they and why are they not listed?  When I do use a spray, I look for the OMRI label on the front.  That means it has been tested by the Oregon Material Research Institute which is located in Springfield, OR and works directly for the U.S. Dept. of Agriculture with respect to their National Organic Program for farmers.   This OMRI label tells you that the product made it into the approved organic program.   Past incidents have been observed when businesses have used other products not listed in their sprays, e.g. malathion.  Therefore, I recommend the pure Neem oil.  Bonide Neem will work and wiping the undersides is fine.  This is your choice, just want you to have more information on sprays.  They are deadly to all insects.  That includes the pure Neem oil.  Treating your plant now is a good idea.  With the rain continuing, I would suggest doing it when it is not raining and then putting a tarp over it for a day so it does not get washed off. Yes baking soda, bicarbonate of soda, same thing.  Add a little Castille liquid soap, no scent in the spray bottle to make it stick better to the leaves.  One tablespoon baking soda, one tablespoon Castille soap in a small spray bottle, fill with water, shake well and often to keep the materials mixed.  Kills like insecticidal soap you buy but you know exactly what is in it.  And to my knowledge does not contain a carcinogen.   Yes to every 10 days at least - 2 weeks might be better.   I cannot get into the article I sent to you either.  I did the day I sent it to you so they probably pulled it for updating most likely. So, Farmer's Almanac is usually a good source for organically caring for plants.  Try this link:  https://www.almanac.com/plant/rhododendrons-and-azaleas   When you Google a plant or plant care put in what you want to know:  "What is this plant?" then add site=.edu to the inquiry.  That will give you university information, not some gardener that has posted online that may or may not know what they are talking about.  University information is researched-based.  Or send me another email.  Good luck with your plant.