Rhododendrons are all very nice, but they sometimes get a bit of bad press, especially in the north and west, where they have become an environmental nuisance, labelled with that dreaded appellation — invasive alien pest.
In the semi-formal ‘American’ garden in Dulwich Park, they are pretty well contained, and, as yet, show no signs of taking over. In fact, they may be having a hard time of things. I took a wander round on Monday (26 August 2013), and found them looking rather disheveled.
According to the Dulwich Park Friends website, the bushes suffered from Phytophthora fungus during 2010. I’m not sure what the problems in the garden are now, but many bushes were covered with mildew, and others appeared dead, with leafless patches and broken twigs. Elsewhere, white waxy patches showed major infestations of cottony cushion scale, Pulvinaria floccifera (thanks Claudia Watts for identifying it from a tweeted photo).
I’d gone looking for the rhododendron leafhopper. There were hundreds of them. I love the way they play hide-and-seek at the leaf edge — sidling out of sight as you approach. If you twist the leaf to reveal them, they sidle back round the other side again. Eventually they get bored and hop away, only to open their smoky grey wings and fly right back to land on another rhododendron leaf a few feet away. Judging by the empty nymphal skins that littered the leaves, the population had only recently reached adulthood.
I also had a look for the rhododendron lacebug, Stephanitis rhododendri. I found this back in 1992, and although I noticed the distinctively damaged leaves for a few years after that, I have not seen the insect for at least 15 years. Thanks to the generosity of the Biodiversity Heritage Library, I’ve been able to download a PDF of my short Stephanitis article published in 1993.
At that time, this pretty lacebug was thought, possibly, to be extinct in Britain, having almost vanished, where 75 years earlier it was common and widespread. I don’t know of any recent sightings, and its absence from the splendid British Bugs website suggests it remains extremely scarce.
Richard Jones
Bugman Jones 
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