Q.Why is my rhododendron being bitten to death?
I planted my rhododendron some 18 months ago, I prepared the soil as instructed. The first 6 months of growing was fine and ever since it has been bitten to death. I have been to the local garden centre and purchased products for treatment as they suggest but still (even in winter) it is bitten to death. It has many flowering buds on it, but the leaves are not a nice looking green in colour. We are in a new build house and when we took posession it had lots of ‘bark chippings’ on the garden, which we got rid of thinking that this may be the cause. Please advise.
Certified GKH Gardening Expert
Are there notches along the leaf margins as if the leaves are being chewed by a pest? If so that is usually due to caterpillars or more likely black vine weevils.
If you think that's the problem, this article outlines organic program compatible methods.
https://www.gardeningknowhow.com/plant-problems/pests/insects/black-vine-weevil-control.htm
Or for chemical pesticide control, my approach would be to combine two systemic insecticides for a heavy soil drench around the base of the plant to be taken up by the roots, one for fast action and another for a longer period of effectiveness. Choose a product with the active ingredient of acephate (fastest but shorter period of effectiveness), and another with imidacloprid (full year control but takes a long time for upatake and start of effectiveness).
The wood chips mulch is usually beneficial, but the weevil larvae can harbor in the organic layer. The insecticide soil drench will kill the weevil larva in the mulch and soil surface.
The faded or yellowed leaf color could be due to nutrient deficiency or soil pH issue (too alkaline), Rhodies like acidic soil conditions. Use a complete organic fertilizer for acid loving plants.
