Jane
Thanks for reading the article. Borers are a never ending fight. If you get rid of one batch there will be others to follow the next year. I do not like to recommend a particular product since what works for one might not work for another. Whatever a person uses must be handled with extreme caution if pets and children are around.
Below is a picture of the two primary products I use faithfully every spring in early April when the first tulips begin to bloom. The Insect killer is "SYSTEMIC", meaning it enters into the plant tissue and attacks the insects from within. The Daconil is a fungicide which I like to use once every summer month, especially when the weather is hot and humid.
I cannot as I said tell someone this will be the "silver bullet": BUT it works for me! And out of about 300+ iris plants It keeps borers in a minority.
Whatever you choose,
please follow the complete instruction on the label and wear personal protective clothing. Insecticides can be very toxic and potentially dangerous. Hope this will help, and excuse me for being overly cautious. (P.S. Ortho has modified some of its products recently to comply with federal and state standards concerning environmental issues. So these might not be available now as shown below.)