Sleeve cage construction
We allowed the crowns to grow for a few weeks before adding the sleeve cages. We used tomato cages to support the sleeve cages, which were made of no-see-um netting to prevent beetle escape and to prevent entry of any predatory insects or arachnids. The sleeves were sewn with a loop at the top to make them able to house a draw-string, and a seam down the side. No-see-um netting is much easier to sew in a regular sewing machine than mosquito netting, since its holes are so small the netting functions much like fabric. Make sure you do not get netting treated with an insecticide; it could cause serious problems with your beetles. We left one pot uncovered per kiddie pool to attract any beetles that might escape so they can be put back into the cages.
The sleeves were cut to have a 1.5 meter circumference; make sure you measure your pots and ensure that the sleeves will be a little baggy to accommodate for the loosestrife plants. We did not end up needing the drawstring loop, but it does provide a nice stiff lip to tie up, supporting the excess fabric at the top. The sleeve cages are approximately 4 feet tall; they are about the right height, but the tomato cages we used to support the sleeves could have been a little taller. The loosestrife grows so fast that some plants are pushing up against the netting at the top. It hasn’t deterred the beetles or the larvae from chowing down on the tops of the plants, so it won’t ruin your project to have cages that are a little short. To close the cages we simply tied a thin strip of netting around the top; it allows you to re-open the cages if needed (for photo-ops!), but holds them tightly closed.
To seal the bottom, the cages can be taped to the pots. We found that Gorilla tape, or some other high-strength tape works best, as duct tape tends to lose its stickiness in rain. We ended up having to tie rubber bands around the bottom of the pots as well as the tape, to prevent escapes. Due to the incredibly rainy spring we’ve had, some netting that came un-taped (thus prompting the installation of the rubber bands), but the merit of an uncovered plant became apparent when a few escapees were easily found and re-caged.
Some protocols for rearing Galerucella beetles call for clothesline to hold up the cages in a strong wind. The use of tomato cages and the ability to set the plants up in an area that is protected on two sides by a building has rendered that unnecessary for our project, but you may want to look into something to support your sleeve cages if you have your pots in an open or windy area.