Beneficial nematodes and butterfly gardens

Princeton, TX

I'm considering using beneficial nematodes to help control the populations of grubs, cucumber beetles and other pesky things. My garden is all organic and it is a butterfly garden with a variety of host and nectar plants. My small farm is a Monarch Waystation and I grow/release various species of butterflies every summer/fall. I haven't used anything in prior years at the expense of plant damage. This year I want to try using nematodes, but my concern is that they might also attack my caterpillars which is undesireable.

I did my research and it seems nematodes will definitely do more good than bad, but I want to keep butterflies safe, including hummingbird moths and sphinx moths that inhabit my farm.
I looked into 2 out of 3 types of nematodes I found:

Steinernema feltiae or Sf - to control mobile insects in the ground. I'm in zone 8b with clay soils so this variety seems to be more desireable for my conditions. Another type is Steinernema carpocapsae or Sc which is very similar but is not being suggested for my conditions/soil type. My concern is that Sf type is also more effective against caterpillars. What kind of caterpillars though? There is a list with insect names and it seems that they attack mostly those in-ground, which means moth pupae. Which means I'd have to potentially say goodbye to my banded sphinxes, Io moths and clear winged hummingbird moths... :(((

The third variety is Heterorhabditis bacteriophora or Hb, they seek out stationary pests, including ant queens which is great. But again, in-ground moth cocoons..?

So, my question is - if I use any one of these nematodes, will I have to sacrifice my favourite moths? How about leaf-dwelling caterpillars? Are they safe from being infected if they touch ground while looking for a spot to pupate? Or should I stay away if I want to keep my favourite moths pupating in my garden? I've researched quite a bit about nematodes but there are still a few bits of information missing in order to be able to make an educated decision.

Thank you very much.

Pueblo, CO(Zone 5b)

My understanding is that the beneficial nematodes work in the soil and only attack the insects that have a stage in the soil. Your sphinx moths pupate in the soil, so they would be at risk. Maybe you could only put the nematodes under the plants that are having soil pest problems, OR group the hosts for your moths with a soil stage and not put nematodes there. I am experimenting with growing marigolds as a green manure to turn into the soil to discourage bad nematodes - that is one if the pests that good nematodes are supposed to get rid of. Since I don't whether or not I have nematodes, it will be a little hard to tell if it works. I was going to grow marigolds anyway - they are the host for a little butterfly we have here.

Princeton, TX

Thank you - that is a good point not to put nematodes near hosts for moths. Grubs and the moths that destroy my false indigo and zinnia blooms are the worst so I was hoping to battle those with nematodes. Also, if I am understanding correctly grasshoppers lay eggs in ground and they have been such a huge problem and starting to be again this year. I've been applying NOLO Bait but ants seems to eat it before grasshoppers get to it. So I don't know what to do next. Nematodes are my plan B :).

And I'll try planting marigolds everywhere as well - I have heard they work well on keeping a number of pests out of the garden.

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