Jim Wilson writes:
> In doing some spring cleanup, I noticed something I hadn't before
> dealt with on many of my TBs in one bed. Several clumps had
> one or two little fans with what looked like black dust on the rhizome
> and in many cases going up to virtually cover the few inches of
> newly growing fan. These fans were brittle and broke off easily.
> The closest diagnosis I could find in The World of Irises is botrytis,
> and it wasn't very encouraging about it. It looks as if the problem
> of finding space may be somewhat reduced this year here.
> All alternate diagnoses or coping advice would be appreciated.
Take it from someone for whom Botrytis is an endemic problem - you've got
it! Clean up all the infected plant material and get rid of it and then
treat the affected clumps and their neighbors with a reliable fungicide,
such as Daconil. That is what I did with the Botrytis that showed up here
during the mild spell earlier this month, and up to the time that the snow
covered the iris up again last Sunday, I didn't see any return or further
spread of the problem.
Jeff Walters in northern Utah (USDA Zone 4, Sunset Zone 2)