Imidacloprid is the stuff to use. My experience seems to indicate that once every 12 mos. is better in climates with shorter growing seasons, but I'm waiting for official research to confirm or deny that. In the absence of firm evidence, it's smart to take the bottle instructions as truth,

One thing you can do to prevent the grubs from coming back is to sprinkle permethrin granules around the base of the plants in March and April to kill the adult beetles before they lay eggs.

Good luck! : )

Sorry to hear it really WAS agaves--not fun at all. I've only used the ready-to-spray Imidacloprid stuff so I can't help you on any of their other formulations, but it's great stuff to use for sure. The ready to use spray suggests reapplying after 30 days I think. In any case, good luck and do keep us posted.

Thanks for emailing me your pics. Below are two of them embedded (I hope) and in the link section is a link to a small public photo album I made that has all of the six or so pics you emailed me just in case some folks can't see the embedded pics.

Calb_gardner's agaves

{{gwi:423628}}

Calb_gardner's agaves' weevils.

{{gwi:423629}}

Sorry again and super good luck. My agaves and I live in constant fear about these weevils, LOL.

Take care,
Grant

Here is a link that might be useful: Calb_gardner's agave weevil pics