From: jwilson@bach.udel.edu (Jim Wilson)
Date: Thu, 15 Jul 1993 13:39:25 GMT

In article <FLAMMIA.93Jul14221901@kuma.lcs.mit.edu> flammia@lcs.mit.edu writes:

> My irises are turning brown, have a sticky liquid at the base and
> white worms in the bulbs. Why and what can I do about it? Also, what
> is the best time to thin and transplant irises?  Katy Flammia,
> Arlington, Mass.

It sounds as if the problem might be iris borers.  They can show up
wherever irises grow, but are particularly a problem for those of us
in the northeast quadrant of the U.S.  The larva are white, shaded
with red above, with a brown head.  They grow from about 3mm to 40mm.
Unfortunately, they are hard to kill with chemicals when they get to
this stage--better is to attack them when they hatch in the spring
with either Cygon 2E or an organic control (Gardens Alive! sells some
nematodes they claim are good for this).  Probably the easiest
approach at this point is to dig and discard the affected plants--lots
of good replacements should be available about now, and then be sure
to take countermeasures in the spring.  If you desperately want to
save a variety, then you might try digging the clump, discarding the
worst parts, then submerge it in a tub of water for fifteen minutes or
so to encourage them to float out, cut away remaining seriously
damaged regions, sun-dry thoroughly (assuming we're working here with
bearded irises), soak (maybe with agricultural streptomycin if rot is
also a problem) and replant.  Be sure to remove all old leaves and
debris in the fall and the spring--you'll likely be carrying away eggs
as you do so.

For most of the U.S., July and August is the best time to divide
bearded irises, although the southerners like to go into September.
September works very well here in Delaware and many other areas for
beardless varieties.

Turning brown can be lots of things.  Some withering of outside leaves
is natural.  You will also see brown spots where borers entered (if my
guess is right).  It is also common to have some bacterial soft rot
where there are borers.  Funguses can make brown too.  You might check
some iris books or the Ortho reference or, better, a local grower to
confirm a diagnosis.