Various communications have been received re iris larvae dying mysteriously, both in captivity and in the wild. Many thanks for these.
'Irisscientist' had captive 4th instar larvae die off this May in a similar manner to my recent illustrations. But Derek Smith, who has bred one or two iris in his time, wondered whether the larva I featured had been predated (I think not: I checked the skin, which seemed intact).
I suspect a wet weather virus, but welcome other people's experiences and views. I'm not an experienced breeder and don't know what I'm talking about here... .
However, in the wet June of 1977 I lost about a dozen larvae (the only year I've tried to breed more than a few) when an orange fungal rust developed on the sallow leaf undersides. I did get it checked up but have forgotten what it is called. It proved instantly fatal. It seems to be associated with wet summer weather (remember the Silver Jubilee rains of June '77?!).
In the wild, grey-white Sallow Mildew Uncinula adunca var regularis develops quite commonly in late summer / autumn on the uppersides of leaves of sallows overhung by taller trees. I suspect it is fatal to iris larvae, though the females seen incredibly adept at avoiding laying on branches / trees which later become affected by it. Does anyone have any experience of this?
Meanwhile, Gentlemen, I am in a state of Severe Nervous Anxiety: Somerset are threatening to win the County Championship... .