How did boll weevil helped the war effort

I don't know about the war effort, but about the weevil itself, it was devastating for the economy, and therefore forced the US. to be less dependent on cotton and diversify their industry towards mixed farming and manufacturing.

The weevil was eradicated somewhere after 1978, so if the war that you're talking about was after that, than it would mean that the weevil made the US. economy more prepared for the war as they now had the better mixed farming and manufacturing processes already set up