How do currant worms / sawflies get around?

Looking for any info / advice on these ravenous beings. I believe these are Euura ribesii, not Nematus ribesii, unless those are synonymous. They’ve taken residence in a row of red currants for years, completely defoliating them if we don’t do anything. When we catch them early it’s manageable but we really don’t want them to spread to our many other currants and gooseberries and become unmanageable. So far they haven’t, and I am wondering why.

Are they present in the landscape and just happened to find one of our rows of red currants (but not the others)? Or maybe they arrived with those red currants from the nursery, and haven’t made it to the other plants yet because it’s hard for them to travel the distance? About 50ft away we have a patch of black currants that has remained unaffected (Ive read black currants are less susceptible but I’ve also seen people reporting their black currants are infested). About a quarter mile away we have other red currants and gooseberries that are so far unaffected. Is it just a matter of time?

Should I try to eradicate the sawflies from that one row of red currants, in case that’s acting as a foothold for them to spread to other areas? We could remove that row of red currants if necessary. I read someone tried to transplant their plants and the sawflies just came along to the new spot. If they arrived with the plants from the nursery about 7 years ago, and could spread to other areas, then I’d think about removing that row of red currants completely to try to eradicate them. But if they are already present in the area and just happened to find this one row and not the others, then there’s not much I can do to prevent them from eventually finding the others, right?

If anyone has any info along these lines please let me know!

How many plants are infested?  If it’s just a few, try spending a hour or two knocking the caterpillars down into a bucket of soapy water and dispose of them.  Easier with two people.

Mk Neal wrote:How many plants are infested?  If it’s just a few, try spending a hour or two knocking the caterpillars down into a bucket of soapy water and dispose of them.  Easier with two people.

This row is only about 8 plants, so ya we’ve been able to manage it pretty easily using the method you described. But I’m interested in understanding how likely they are to find our many other currants, which would make it a lot harder to manage. I’m hoping that at least the black currants aren’t susceptible, and that the sawflies have a hard time dispersing to plants that are further away, and that perhaps they arrived on those plants from the nursery as opposed to from my surrounding area. That might explain why they have been seemingly isolated on this one row for years. In that case I’d want to remove that row of red currants completely and hope the sawflies die out.

Jay said, "But I’m interested in understanding how likely they are to find our many other currants, which would make it a lot harder to manage.

Maybe this will help explain:

Adult females use their saw-like ovipositors to cut slits into needles, leaves, or tender new shoots to lay eggs. Eggs hatch into larvae that feed on foliage of their host plants for about four to six weeks.

https://extension.umn.edu/yard-and-garden-insects/sawflies

Maybe you can find something they like better than currants and plant that to keep them off the currants.

Anne Miller wrote:

Jay said, "But I’m interested in understanding how likely they are to find our many other currants, which would make it a lot harder to manage.

Maybe this will help explain:

Adult females use their saw-like ovipositors to cut slits into needles, leaves, or tender new shoots to lay eggs. Eggs hatch into larvae that feed on foliage of their host plants for about four to six weeks.

https://extension.umn.edu/yard-and-garden-insects/sawflies

Maybe you can find something they like better than currants and plant that to keep them off the currants.

Thanks, that helps. I’m still looking for info about how they might have got there in the first place, and why they haven’t spread to our other nearby currants. They’ve been there long enough that I would expect them to have found the others by now.