Re: Iris Borer

Cygon 2E has been replaced with Lagon, same product, different name, but you need sprayers licence in Canada, probably same in USA. This is a systemic, gets absorbed into leaves., and is eaten by anything eating leaves. Needs to be applied very early in spring, when plants are just starting to grow. Dormant oil spray, very early in season will smother eggs before they hatch. Any insecticide that is not systemic is useless.
Hunting and squishing is not as time consuming as it may sound. As you are going through iris garden, keep a watch on foliage, at top of separation point of leaves. A sign on borers is damaged leaves coming out of growing tip, and green plant sawdust. Seperate leaves and look inside split were leaves seperate. A tiny borer will be found. Then just squish them. This can be done around time of flowering. Squishing outside of leaves doesn't work as borers are inside the hole they have eaten, and are protected. Just get in habit of looking at plants as well as flowers.
I burn foliage in spring, just as soon as foliage is dry enough to burn. Plants may look awfull after burn, but plants bounce back quickly. I have a series of photos of Siberian iris spring burn, showing foliage before burn, the burning, after with the charded remains, several of growth through the season, and plants in full bloom at proper time. I also burn large TB clumps, same result. Not only does it kill borers, but also weed seeds around plant, which are weed free in spring where fire extended. 

Chuck Chapman

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