Answer: Iris borer can be difficult to control and most gardeners find they need to follow several steps to save their planting. The first and most important is follow good sanitation practices -- I can't emphasize that enough. Next, if you have certain varieties that seem especially prone to the borers then consider discarding those varieties. Next, treat with spinosad or beneficial nematodes being careful to apply them at the appropriate time of the year. The following web page includes detailed information you will find helpful. You may need to cut and paste the complete url into your browser to make it work correctly.
Good luck with your iris!
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