Iris Borers

     Well, I'll un-lurk to join this discussion...
     
     I grow irises in Massachusetts (zone 5, more or less, about 35 miles 
     south and inland from Boston).  For most of us in this area, iris 
     borers can be a real problem, especially in our smallish, relatively 
     intensively-planted iris gardens. Most of the growers in my region use 
     some sort of chemical control (Cygon and other systemic insecticides) 
     to control the borers. The fact is that even if you remove the soil 
     and sterilize it, or heat sterilize it (with plastic) in place, or 
     plant in a new area that has never seen irises, you will still 
     eventually end up with borers if you are growing only one crop in that 
     area for any length of time.  Crop rotation, the means by which 
     farmers try to battle this phenomenon, is usually not an option (we're 
     dealing with perennials here after all, and we don't usually move them 
     every year; I don't have enough iris beds to do that anyway!) 
     
     But, I HATE USING POISONS.  So, I've been trying to find alternative 
     remedies for my insect and disease problems. (I grow hundreds of 
     irises, but I also grow my own veggies, and I'd just rather be as 
     organic as possible about the whole thing.)  Well, I don't know if 
     anyone else has tried it, or if it would be as effective for others as 
     it has been for me, but I seem to have found an organic control for 
     iris borers - beneficial nematodes.  
     
     I originally got them as an attempt to control what had become a 
     Japanese beetle invasion (It was bad; in mid-summer you could walk up 
     to one of my peach trees, shake it, and watch a cloud of beetles fly 
     out - yuck!  The leaves of my beans were turned to lace; they made 
     swiss cheese out of my basil; white roses got chewed up while in bud; 
     they chewed off the corn silks, making pollination spotty and causing 
     the ears not to fill out properly - it was REALLY bad!) I've sprayed 
     the nematodes (available from Gardens Alive!) onto the yard and 
     gardens in spring for the last three years running. Now, the Japanese 
     beetles are down to a few hardy souls (definitely manageable) and I 
     haven't seen more than a couple of iris borers in the last couple of 
     years. 
     
     The nematodes parisitize the grubs while they are in the soil, so 
     timing is important.  Once they've entered an iris rhizome, I doubt 
     the nematodes can get at them.  In zone 5, a fall application would 
     probably also work, but the nematodes are not winter-hardy here and 
     our freezes are VERY unpredictable, occurring both early and late, 
     making it a bit more difficult to time it right.
     
     Well, the verdict is that it may be kind of expensive, but it works 
     for me.  Anyone else had any experiences (good, bad or inconclusive) 
     with beneficial nematodes as an iris borer control??
     
     Stephanie Markham (smarkham@meridianmktg.com, going organic in 
     Massachusetts)
     
     _________________________ Reply Separator___________________________ 
     From: SCHAFFCM@SNYBUFAA.CS.SNYBUF.EDU
     To: iris-l@rt66.com
     Subject: Re: Irisborers (not Kathy)
     Message-ID: <01I9TERP8WZC90YQ1X@SNYBUFAA.CS.SNYBUF.EDU>
     
     
     Rich -- among the other suggestions you will get might be one to 
     completely
     remove the existing soil, sterilize it to get rid of borer larvae in 
     dormancy
     (or whatever you call it when they are cacooning down in the soil) and
     put in new soil -- at this time of year, they are ready to come out of 
     the
     soil and become moths and start laying eggs.
     
     OR__ move the bed... put the iris where no iris has gone before -- 
     which kind are you putting in? bearded or beardless??
     
     Carolyn Schaffner in Buffalo, NY who knows a local grower who removes 
     the
     soil where he is going to plant new T.B's and puts in bags of soil 
     from a
     nursery and swears he has no borers!!
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index