Milkweed Stem Weevils

[pjvanee]

I am a new member who has already gotten lots of great information from your site. I have a huge problem with milkweed stem weevils attacking my swamp milkweed. In past seasons the stems were so scarred from the weevils that they frequently broke off while I was looking for eggs. In addition, most of my seedpods were destroyed by the weevil larva before I could successfully harvest them.

My swamp milkweed has just begun to sprout for the season, and I have many new varieties in the basement, under lights, waiting to be planted. The monarchs are still weeks away, so I'd like to get working on an organic solution to the weevils before the new plants are planted and Monarchs finally arrive in my area.

Any ideas?

[Mona Miller]

The only thing that I've been able to do is locate them and squish them. They are ugly, gray, hardshelled, very small weevil that cut the top of the stem. They lay eggs farther down the stem. Their larvae is what does the damage to the roots and stems. Apparently, they cut the top of the stem to drain out most of the latex so they can get on with their egg laying.

http://www.texasento.net/Rhyssomatus.htm

http://www.monarchwatch.org/forums/view ... 1490#p6976
This post has some good information.

[pjvanee]

I have had great success controlling the milkweed beetles by handpicking them, but the stem weevils are very quick to drop off the plant as soon as they are threatened. Most times their reflexes are quicker than mine, and once they hit the ground they are camouflaged in the soil. Very early last spring I dug up all my swamp milkweed plants and soaked them in water for a few days before transplanting them to a new garden location in hopes of drowning the overwintering weevil. Not only did they survive the water treatment, but they also caused record damage to my milkweed stems. I am hoping for a non chemical solution, but seem to be running out of options.

[Paul Cherubini]

To learn about chemical insecticide solutions that professional monarch breeders use and are safe for monarch caterpillars see my posts in this thread: viewtopic.php?f=7&t=198

These posts are mainly about aphid control, but the Malathion may also be effective against your milkweed stem weevils.

[pjvanee]

Thanks for the Malathion advise. I am sure it would be effective, but the smell of it makes me ill. I am hoping for a more organic control. I did some more research on my own and found out that beneficial nematodes and diatomaceous earth are effective against weevil larva in the soil. I just do not know if the milkweed stem weevil larva spend any time in the soil, or if they mature in the stems. If all else fails I may have to use pyrethrin at ground level in hopes of getting the weevils under control before the monarchs arrive.