Hi Chris,

There's a lot to unpack with your questions. I'll do my best to address them all.

Biocontrol: I don't think that Galerucella beetles are commercially available. Most people and organizations have to collect them from established populations. The Minnesota DNR has a nice guide on how to collect and release loosetrife beetles. https://files.dnr.state.mn.us/natural_resources/invasives/aquaticplants/purpleloosestrife/pl-biocontrol-how-to-collect.pdf

Herbicides: Herbicide sprays are only one of several methods for removal. Due to limited resources, land managers typically have to perform a cost-benefit analysis for each management tactic. For example, in situations where the infestation is small and isolated, manual removal or hand-wicking are reasonable choices. With large infestations, most land managers would tell you that the labor costs for manually removing or hand-wicking each individual plant would break their budget. Moreover, if it's a severe infestation, it likely that the loosestrife has already crowded out most native species. In these cases, herbicide sprays are very cost-effective and collateral damage to native species is incidental.

Herbicides require special labeling for use in aquatic environments. I'm not certain how many of these herbicides are available to the average homeowner. It has been a long time since I've worked in ecological restoration, so I'm not as familiar with aquatic herbicides as I used to be. Regardless, applicators are obligated to read the label before spraying. It will let them know if it's OK to spray on their site.

If you haven't seen it, check out this management guide by the Ontario Invasive Plant Council. It does a nice job of articulating the calculus of selecting control strategies and lays out a good set of BMPs for purple loosestrife.

https://www.ontarioinvasiveplants.ca/wp-content/uploads/2016/07/Purple-Loosestrife-BMP-April-2016-final.pdf

Hope that helps!