PC emerge from soil esp. when temp gets warmer at night. I don’t know how you could get rid of them before they emerge. Soil drench? How large of an area to drench?
One possible way is to net and gather the botom of the net against the tree trunk and tie it tightly. This way, PC emerging from the ground cannot get in.
I am reluctant to use a regular sprayer as it may get clogged. I have a big old fashioned watering can with a shower head which I use to disperse them. Depending on how large your area is divide the nematodes into batches for a series of refills of the watering can.
This year I think I wasted a lot of $$, I got the bright idea of putting them down in the rain so I wouldn’t have to water so much, but after I put them down it turned into a massive downpour and it probably washed most of them away. 
That’s a bummer. Which nematodes did you go with? I was going to pick up both types you mentioned in a previous thread. Curious if you just get one type or if you combine the two you previously mentioned?
In my opinion, at least around here, any drench for curculios is going to be defeated by the following. Carolina Cherry, a wild Prunus, native to SE Georgia is subject to curculio and its one of the most common weedy trees in the area. Curculios and stem canker are coming at me from every direction. I’ve eliminated most of the fruiting sized wild cherries (both black and Carolina) from my property, but every yard and thicket around me is just full of them. One really has to focus on spraying the tree. When I do finish spraying I do spray the ground right around the trees with Malathion right at dusk. I like to think it helps a little. But seriously, I’m surrounded by curculio infested Prunus trees. I simply have to treat my trees. God bless.
Marcus
I’m 2 hours away from you and plan to implement the suggestions from you and @scottfsmith next year. Brown rot, OFM and PC devoured pretty much all of my fruit this year. Next year will be the first year I implement a spray schedule and I hope to actually get some edible fruit (if I can keep the squirrels away). Appreciate the sage wisdom both of you have provided!
Unfortunately this also creates a perfect brown rot environment - tree becomes to crowded in the net if you do not provide a spacious frame for it, and if you do, it is problematic to tie it aground the trunk - believe me , tried many different things, so far can’t find perfect netting technique… Hmmm … I think I just got and IDEA! If I make my net a cube, opened on one side, I can put it on the tree, not on the frame, but use clamps to attach it to the frame from inside, leaving bottom portion free so I can tie it around the trunk. It just has to be long enough to make that angle…
I got both types again this year.
The Cornell results on the nematodes were something like 50% reduction if I recall, probably some of this is from the fact that the curculio can come in from nearby areas. I don’t have much in the way of other good crops for them near my house so I am hoping to get 50% reduction or better once I figure out the timing and application.
This year I finally got my mating disruption working well, OFM damage has been much lower than usual. I did a much broader placement and also put them up earlier than I had in the past. With these kinds of non-spray controls it takes awhile to get the hang of them.
The Robusto is the only plumtree that I’ve gotten that’s on peach rootstock that has lived more that three years. I think something, possibly nematodes, possibly borers first weakens the root stock, then stem canker takes out the whole tree but starts in the scion. The trees did seem to show sign of disease from the bottom up rather than from the top down. The Euro plums did not last long either, but they seemed to die of stem canker or something similar from the tops down, and then the Mariana rootstock persists and suckers, and in the case of one tree, becomes my best plum tree. I’m thinking using a plum root stock and resigning one’s self to having to mow down suckers regularly is the way to go. It makes for bigger trees. But for the life of me I don’t see the benefit of the peach root stock, at least not here. I say use a seedling from an improved Chickasaw for Asian and Chickasaw types and Mariana or maybe Monson or possibly hog plum if you don’t want suckers for everything else.
Oh, that reminds me. I need to go out in the woods and look for hog plums for seeds. I want to see how easy it is to graft on since they do not seem to sucker at all. God bless.
Marcus
What is your mating disruption strategy? I haven’t seen a thread related to this (probably missed it).
I’m not sure I mentioned it anywhere. I put out the lures over a wide area, not just in the fruit trees, and I put out about double what they recommend for larger areas. To cover a lot of area I have them in bushes, attached to the house, trellises, in adjacent woods, etc. Also they should be put out at bloom, I was putting them out a bit later in past years so they would last longer through the year but that I now feel is a mistake.
Does anyone have any advice about using the new formulation Sevin for PC control? I noticed that Mustang Maxx, with the same active ingredient zeta-cympermethrin, is rated effective (4 out of 5 on a 1 to 5 scale) for PC control according to this table on page 9 from North Carolina State.. It’s also rated as very effective, their highest rating, for OFM. I used two sprays of Malathion this year on peaches and plums with not great results.
I have no experience with Seven. I still use Malathion. I spray once a week at dusk starting not long after the fruit drop the husks of the old flowers and stopping when they are a little bigger than a nickel. Mariana is way to big for me to spray the whole tree, but when I spray the limbs I can reach, all the other prunus trees around her and the ground under her as well at dusk, I get good results. With Malathion I think the key is spraying at dusk and spraying the ground. It seems to be OK to not be Able to reach the top of the tree. Personally I think the curculios hang out on the ground during the day, so it just might only be important to spray the ground under the trees. God bless.
Marcus
Whatever you do I think spraying often enough, spraying the ground and spraying at dusk are three important components of effective curculio control if your weapon is malathion.
For those interested in organic control of PC, a long study on the use of Entomopathogenic (insect-attacking) nematodes (or EPNs) concluded and its results were published here (opens to PDF) starting on page 11.
The idea was to use native cold-hardy nematodes that attack PC larvae, establishing a colony by spraying just once a year and allowing their numbers to grow naturally. Cost worked out to be $80/acre I believe. Results were mixed but sound substantive enough that if you’re dead set on organic it’d be an option worth exploring.
I saw that study awhile back and have for a couple years sprayed the nematodes they recommend. I didn’t notice a big difference unfortunately. I might have messed up the application which is why I tried it again after the first time didn’t work.
I am trying a new product called Venerate XC this year which is supposed to have some action against both PC and moths. See the following thread.
I am in Zone 7 Northern VA. My Beauty plum tree is in bloom now due to the unbelievable warm winter. I never sprayed anything on my plum, but this year I want to give it a try and hope to get better fruits.
After reading the articles online and posts on this forum, I still don’t know what would be the best spray to control PC.
I know Surround works well, but it leaves white coating, which is not good in my case because my tree is up front. I know my neighbors will start worrying and asking questions if the tree is heavily covered by white coating. 
I am OK with non-organic solution. So I found the following 3 options:
Malathion is pretty safe if you spray at dusk and are careful.
I wish I knew I bought the New Sevin with Zeta-Cypermethrin - 0.35% Plum Curculio is listed as a kill as is most everything.
Thanks, Marcus!
I will give it a try because it delivered good results for you.
Did you buy a specific product?
I am thinking to buy this one:
https://www.amazon.com/Bonide-BND992-Malathion-Concentrate-Insecticide/dp/B000OW94Y2/