Red Lily Beatle

My asiatic and oriental lily bed (about 25 plants) is now 3-4 years old and did extremely well until this year when it got hit by red lily beatles. I kept them reasonably under control by picking off the beatles and larva pods but the plants did suffer and the leaves seemed to have turned brown earlier than usual. I intend to put all the stalks in the trash but suspect the larva will overwinter in the soil. I have three questions: 1. Is there any treatment for the soil to prevent overwintering of the larva? 2. What should I be doing next spring and summer to get rid of these pests? 3. The bed is becoming overcrowded so I want to thin them and also start a 2nd bed with the left overs. What is the proper way to do this? Should it be done in the fall before freeze-up or can I wait till spring? I prefer the spring as my 2nd bed will not be ready until then. I am in zone 4b. Thank you.
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I posted the following several weeks ago but got no replies. Maybe an expert will see it this time:
My asiatic and oriental lily bed (about 25 plants) is now 3-4 years old and did extremely well until this year when it got hit by red lily beatles. I kept them reasonably under control by picking off the beatles and larva pods but the plants did suffer and the leaves seemed to have turned brown earlier than usual. I intend to put all the stalks in the trash but suspect the larva will overwinter in the soil. I have three questions: 1. Is there any treatment for the soil to prevent overwintering of the larva? 2. What should I be doing next spring and summer to get rid of these pests? 3. The bed is becoming overcrowded so I want to thin them and also start a 2nd bed with the left overs. What is the proper way to do this? Should it be done in the fall before freeze-up or can I wait till spring? I prefer the spring as my 2nd bed will not be ready until then. I am in zone 4b. Thank you.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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