I can only see the one picture and the link is broken.

The Cranberry Rootworm, Rhadopterus picipes, chews holes in the leaf, some of which are crescent shaped. Shiny and black with a greenish sheen, these beetles are about 3/16 inch long. They feed at night and hide in litter or under containers during the day. Beetles damage leaves by chewing oval-shaped holes. They are usually associated with container nursery stock in areas with dense shade. Remove ground litter and weeds from the area and reduce shade where possible. Treat late in the day and repeat once or twice weekly.

It looks like your rhododendron's roots have lots of competition. Rhododendrons have very shallow roots and don't compete well with other plants. I would pull out some of the plants in the rhododendron's drip line, being very careful to avoid disturbing the rhododendron's roots. Then mulch well. The mulch will keep other plants from coming into the rhododendron's space, as well as conserve moisture, keep the roots cool in summer, and avoid ground heave in winter.

The pH looks OK. Right now, I might apply a little HollyTone, but at half the rate on the package and just once. If the rhododendron has too much shade you are lucky you got one flower. They need some sun, several hours a day, from now until mid-summer to form next years flower buds. If shade is the problem, you have two choices, thin out the shade or move the rhododendron to a sunnier location.

Here is a link that might be useful: How to grow rhododendrons and azaleas

Thank you, rhodyman. When you say treat late in the day and once or twice a week, what am I treating with? I am going to take your advice and move the plant, too - hopefully the beetles will not follow! Thank you for the link.

BTW, tried my link and I can see the other pix; now I've got to figure out why you can't!

This assumes a contact insecticide approved by our county agent. Possible pesticides include Carbaryl, Imidacloprid, Permethrin, and Spinosad. Besides applying at night when they feed, spray the leaf litter below the plant where they hide.

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