Re: Leaf Borer

Peter Goodfield wrote:
> 
> I've received so many conflicting pieces of advice about borer control, I
> hoped those on this dedicated list could provide a legitimate definitive
> response...
>      Two years ago, when my irises were badly affected by borer, I posted
> a note on compuserve's gardening forum asking for suggestions...malathion
> was suggested...of course, this kills just about everything, beneficial
> and malevolent...the next year, I again posted a note, and Cygon was
> recommended...obviously, this too is not a natural disease controlling
> agent, but on the other hand, I would like to be sure I don't again
> suffer the heartbreak of borer...
>      Could some of you "out there in cyberland" please post some
> suggestions as to how you've controlled borer (other than just clearing
> out the debris from the ground each year)...the more specific, the
> better, i.e. when exactly to do what, how often, etc.  Many thanks!
> Peter Goodfield in N.C.

Peter -- Keeping a clean bed is important, but the borer moth is still
going to lay some eggs. The time to destroy the larvae of the borer is
in late winter/early spring. Where you are, in North Carolina, this
might be as early as February, depending on where in the State you live.
Watch your plants for signs of new growth, and when you see it, spray
the plants with Cygon 2E. Cygon is a systemic and will zap the
microscopic little devils as they climb up the fan to begin their
chowing down. My opinion is that spraying too early is better than too
late. Different varieties of iris will "green up" at different times, so
I would advise taking the early ones as the signal to begin the
spraying. My opinion, again, is that just one or two really warm days
when new growth is beginning is suffient to "hatch" the larvae. I make
two passes, from different directions, down a row of iris to ensure
spraying both sides of the fans, and I use the spray liberally, i.e., I
soak 'em. I usually only spray once. There is, of course, some element
of luck in the timing of this, but in an ordinary year, I find borers in
only about a dozen of more than 1,000 iris.

Some larvae somehow, as just noted, will escape the treatment. The sign
is usually a serrated leaf edge and maybe a dark, wet streaked
appearance to one or more leaves. The borer enters the leaf after
munching the edge and works its way down the leaf into the rhizome. I am
told, and believe, that you can still destroy the borer before it
reaches the rhizome by finding it and squeezing the leaf until the borer
is squashed. I am not sure that I have ever succeeded in this. As in so
many things, Clarence is reputed to be an expert in the art of
borercide. I think I recall seeing a series of photographs published a
few years back in which Clarence stalks and dispatches the prey. He
apparently has the "touch" and I leave it to him to advise you further.

Griff Crump, along the tidal Potomac near Mount Vernon, VA 
jgcrump@erols.com
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