Doing some research on Growing Degree Days (GDD) I found the following useful. It is based on apples but that shouldn’t matter regarding Plum Curculio life cycle.
Weather station for your area and petal fall date must be selected to get accumulated GDD. The PC cycle based on apple petal fall is 308 GDD. I’m at 80 GDD (on May 16) and oviposting is currently predicted which is correct since I’ve seen some marks. I can monitor GDD and stop spraying as I approach 308 GDD assuming they are correct.
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Hard to believe no one posted about PC in 2023 till now. Knock on wood. I barely found a PC mark this year and only sprayed once. I guese that’s the one saving grace for having nearly 0 fruit set the previous year.
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Same here. This year is strange, I don’t see PC bites on plum, peach/nect, not I am asking for it. I am highly alert on monitoring possible PC activities at this stage of fruits development. It makes me undecided whether to spray or not. Where did the PC go?
When night temp is in the 60’s, they will emerge in droves. Some emerge before that but more when it gets warmer.
I don’t wait. I spray proactively because I know I have them here.
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Tippy ,maybe they have a reunion in the east😂
Im pretty sure they skipped out on you guys and came to my place. I’ve been behind on spraying and already have some crazy PC activity. If I loose 90% or more stonefruit im switching to some heavy duty pesticides next year.
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Hope they like the upper midwest more 
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In the mid-atlantic regional thread we have been discussing PC, plus I think it has been on some other threads … just not on this one.
For me it’s been a normal year… some things strangely untouched and other things strangely bitten to death. I lost maybe 2/3 of my apricots in the early freezes and the PC really picked on the remaining ones. I’m not going to get many fruits at all. Other than the cots the damage is a bit less than a usual year. The weather has been cooler lately which has helped; it was almost a month ago that the PC was rampant in the early heat waves and that was also when the apricots were the main target.
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Maybe the Midwest dry weather suppressed the PC activities. We have no had a good rain for awhile, and is not in forecast for another week. Night temperature in mid 40s to upper 50s range.
Should I wait till after the next rain to spray pesticides?
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They did seem to avoid my fuzzier peaches for the most part. No cherries were touched either. Nectarine, nectaplum, peacottum, pluerry, pluot, plum were all well sought after! Hell last year they even went after the black walnuts!
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I saw some last year, I’ve treated the soil twice now though, early and late, with beneficial nematodes and I’m hoping they do their job. I haven’t seen PC yet.
I lost a lot of fruit to late freezes. The plum curculio pressure was also bad this year for me. I sprayed 8 times with permethrin (the most I have ever sprayed by far) and still had a lot of feed bites from pc. Almost no crescent shaped egg marks. On the trees that survived the freeze damage I will have a fair amount of fruit, some of it will be ugly from the pc scarring. I am located in the Piedmont region of Virginia. I feel that imidan would have done better with the PC but we had constant rain and permithrin stays on the fruit longer than imidan in the rain.
There being no next rain in the forecast, I have started already to spray. Bagging apples and pears will have to wait till fruit drop. Thinking of those organza bags for the few stone fruit that set. Maybe I might get one to eat.
I thinned apples very early to size up my keepers fast so was able to bag 500 apples after only two Surround sprays. I’m now on easy street except for cutting out blight every day.
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I have been thinning my Asian pears for several rounds already. Started with pinching off smallest unopened flower in the cluster, then taking off lastest bloomed flower;then taking off smallest fruitlet and any damaged fruitlet; then thinning to 3 per cluster; now 2 per cluster. Nextis 1 per cluster. Thinning is getting tougher and tougher when only one fruitlet can stay.
Every time I went out to the yard, I brought back handful of little fruitlets. There os no hope for the peaches this year. Plum is light too. Asian pear is more dependable even though the fruit set is light.
@ltilton , you are right, I should keep the spray schedule. I saw a green stink bug on my window screen today. This bug does number of damage to fruits too
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I used imidan maybe 6 times so far. More than usual but it rained heavy soon after spraying multiple times. I’ve seen less PC than usual. I’m in the Shenandoah valley of Virginia.
The good thing about your location is that you aren’t losing all your stonefruit to late freezes like here. I know it’s still a challenge with insect and disease pressure though.
I hope you have better luck than I did. I spent $250 and didn’t see any appreciable difference. There are many factors involved in getting good results with them so it is certainly worth a try but don’t count on anything.
I hope I am getting near the end of curculio season. But with Surround I learned to keep the coat up into early June, I have had too many late attacks. I just did another spray last night.
BTW on the subject of treatments for curc I have been using Grandevo and Venerate in my Surround tanks since they are supposed to have some effect on the curc. I haven’t noticed a huge difference there either but they also have some control for other things such as SWD OFM CM etc so I am going to keep using them.
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I’m not sure how bad the pressure will be, the nematodes might be enough for now but we all know that the longer the tree is there, the more nasties arrive.
being in the region I’m in makes it better I think. though we’ve got to spray for lots of other things
Ah you are in the PNW… don’t worry be happy, they are not established there yet. They will one of these years for sure though.
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Ageed. No threat here in Spokane.
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