curculio progress

Has anyone found any issues mixing Grandevo into the core holistic recipe? (i.e., neem and/or karanja, soap, EM, molasses, fish, etc.) I'm assuming not, but thought it'd be good to ask twice and spray once.

Earthworks
Zone 7a in West-Central MD
Non-commercial, ~100 fruit trees, dwarf to MM106

We applied Grandevo last week for the first time within a variation of the core holistic recipe, and had no mixing issues. It seems to break down into the spray solution very rapidly. For what we were applying, we did make sure and follow basic rules of when to add different types of mixers, so wettable granules, like Grandevo, came first, and the oils emulsion was the last thing to go in the tank, but still when the tank was only half full and had a ways to go, fill-wise.

Note, we did not apply EM-1 in this cocktail because another bacterium we were adding would likely have had action against the EM-1, or alternatively, the EM-1 could have done what you hope it does, and occupy space in the canopy where we wanted our more specific bacterium to take hold. I felt OK about applying Grandevo with it because of the specific modes of action involved, but don't forget to think about how various biologicals will interact with one another, both in the spray tank and in the environment. I wouldn't expect the bacterium in Grandevo to be incompatible or particularly competitive with EM-1 (or vice versa), but sometimes it's just as well to get some guidance. We spend a lot of time on the phone with reps for any companies we buy products from, asking if they've done compatibility testing or if not, if they would expect compatibility to be an issue. So for example, in a different potential tank-mixing situation we felt OK about tank-mixing Agriphage with Grandevo after the Agriphage folks let us know that they had not specifically tested Grandevo with Agriphage, but had tested other products containing the same type of bacterium, and found no issues (we still sent them a Grandevo sample to test definitively for the future). Sometimes it's not a matter of bacterial compatibility, but whatever else is in a formulation with the biologicals that can negatively affect other biological components you're mixing.

Kordick Family Farm
Westfield, NC
Zone 7a



Edited 3 time(s). Last edit at 04/29/2022 03:05PM by Brittany Kordick.

No problem mixing. I'd just make sure it goes through a good screen because it appears it could clump--but not severely.
Brittany brings up a good point with competing organisms. A major driver of EM application is to provide such severe competition for the baddies that they can't thrive. That can equally apply to the good guys, or benign. Brittany, I'd be curious to know which of the good guys you have found or suspect are incompatible and why. I'm surprised the vendors would share much of that info because if this truly is a big issue with biologicals, it's not a simple one and they would spend quite a lot of resources figuring it out. Somebody like Tainio who have been around a long time have some 19 specific microbes in their Spectrum.

Agreed, mixing beneficial microorganisms is necessarily really complicated, and being that it's been so much on our minds as we get into spray season, just thought I'd mention it. A lot of the reactions can't be quantified out in the orchard environment, where the success of particular microbes establishing depends on so many variables; a lot of decisions we make about biological mixing is just taking as much info as we can get and ultimately going with our gut. But it helps to anticipate any potential issues. We're spraying today ahead of a rain event and found ourselves looking at whether or not we wanted to add EM-1 to a tank mix that will contain, among other things, Grandevo and a Pseudomonas containing formulation. We ultimately decided that we would wait til the next spray to add in EM-1, not because we think Grandevo and/or the Pseudomonas will not be compatible, but because we're applying the Pseudomonas for the first time this season and have particularly high hopes for it helping to control fruit rot infections -- we want it to get a good toehold in the canopy that we'll supplement with further applications. Going forward, we'll add EM-1 to the mix, but we would prefer for the population to be skewed with more aggressive bacteria like the Pseudomonas at the moment.

Of course, some reps are more helpful than others -- if they've done the compatibility testing (and as biological products gain in popularity, there seems to be more and more compatibility testing being done), they're happy to share that info, and sometimes, if they have solid microbiology backgrounds they are more willing to speculate, but of course, they have to protect the company they work for, too, and if they have no idea, won't necessarily go out of their way to think through your biologically complicated questions. As Don stated, some of these broad beneficial bacteria mixes may contain one or two dozen different microbe species. They all have different wants and needs, and fill different roles in the environment, which makes it particularly hard to anticipate what will ultimately happen out there. But they tend to be space taker-uppers that benefit the trees in passive ways like making nutrients available. When you purposely add more aggressive microbes to your mix for specific pest/disease control reasons, it stands to reason that they will affect/be affected by what you've got out there or are putting out there (this is why you might at times feel a need to create a blanker slate before inoculating with certain species, whether with a fatty acid knockdown a la Michael, a broad spectrum bactericidal application of Oxidate, etc.). For example, we applied a saprophytic fungi-containing product in the orchard specifically for early pathogenic fungi control during the cool season. We knew there wouldn't be much point in applying EM-1 surrounding those applications since the sap. fungi would likely annihilate those more benign species. But the sap. fungi in question is a cool climate species and will inevitably die off as temperatures rise, so once the big infection window closes, we can refocus on general beneficial bacterial colonization.

Kordick Family Farm
Westfield, NC
Zone 7a



Edited 1 time(s). Last edit at 04/29/2022 07:06PM by Brittany Kordick.

Owing to the high cost in Canada of the product discussed here, I opted for the trap tree approach using leftover pieces of last year’s frozen plums as bait, hung in net bags, with a white sheet stapled to the ground beneath the tree. Unfortunately my plan did not work because I have an early fruiting apple tree next to my plum tree, so the curculio went to the apple tree instead! On the positive side, I was able to see and kill quite a few curculios on my apple tree- I had never seen one before, just the results of their visits.

We're finally past prime plum curculio time and can try to gauge the effects of our Grandevo apps this spring. We applied 2 lbs per acre twice surrounding petal fall, and felt like our timing was perfect. We were just starting to see the first stings in fruit, but not widespread damage. One thing about Grandevo to keep in mind is that it's slower-acting and it may be days after application before pests are affected. The curculio (and any other pests you may be applying Grandevo for) has to ingest the Grandevo and it will act primarily as a stomach poison on it. Still, the label indicates multiple modes of action affecting oviposition, feeding, and reproduction. We were dismayed at how much curculio damage we continued to have after the applications (looks like fairly normal incidence in our orchard), but it will be interesting to see what our long-term effects are. Assuming the adults were able to oviposit after or during exposure, were the larvae at least adversely affected? It's tempting to say that we are seeing less June drop due to curculio, but it's difficult to say since we are seeing normal to higher drop in certain varieties presumably due to an ongoing drought situation and some overcropping. In our surveys of the fallen fruitlets, it seems like less have curculio stings than usual, lending credence to the idea (and hope) that the reproduction process was affected, so less larvae triggering fruitlets to abscise from the trees. We're hopeful that we will see reduced pressure next spring, but somehow we didn't expect, as we perhaps should have, that to large extent, the plum curculio actually has to oviposit (or attempt to oviposit) in order for the Grandevo to take effect.

Kordick Family Farm
Westfield, NC
Zone 7a



Edited 1 time(s). Last edit at 06/13/2022 05:45PM by Brittany Kordick.

I too have had the same experience with using Grandevo for the first time this year Brittany. I used it by itself one day after a holistic spray. I know Michael mixed it with Surround, but it sounded like Don didn't last year and had great results. Applied it at petal fall and I think maybe that's too late. Major damage to apples, pears and peaches. Here in Ct. they seem to come out in one night and ravage the place! This is really the first year I've been managing this small 46 tree orchard that grows fruit for local people in need, so it's very much a work in progress. I was lucky enough to attend Michaels last intensive orchard class and am trying to go that route if possible. Any advise would be appreciated.

I’ve found that the first evening after petal fall that remains above 70degrees the PC will be moving and stinging. Not much to sting at petal fall but a week later. I don’t think you started too late but maybe missed that one evening. It only takes one night as you just saw. My experience comes from the time I used to use Imidan and had no PC if I got it right. Surround does a good job if you can get it on with 3 coats.Also good on CM first generation.
Keep feeding people!

PC is a tricky one because we do not have really good monitoring tools (e.g., pheromone traps) and the insecticides that we have are marginal at best. It is a pest that, as Alan points out, likes those first warm nights and can do a lot of damage in a single night. For me, PC requires a multi-pronged approach and multiple applications of different insecticides, esp in this age of extended bloom periods due to late blooming varieties. As well, climate change and weather variability means that the biology of the pest is also likely shifting to become more complicated. What we do know (as best we can) is that PC is active for roughly 309 DD following petal fall. Not that it disappears necessarily, but that it is less active (to not at all). When we have these extended bloom periods, that means there are "more" petal fall timings that we need to be aware of and that our insecticide applications need to take into account these variations, as well the potential impacts on pollinators. If we wait until all varieties have bloomed, then the earlier ones will get hammered. If we treat the earlier blooming varieties once they are at petal fall, depending on the material, we run the risk of harming pollinators. So, my strategy is evolving to become one of distract, deter, and kill, and treating the varieties with deterrents as they hit petal fall, while leaving others that are in bloom alone (or at most a Surround application). What does this look like?

Tight Cluster-Pink: Surround 25 lbs/acre
Bloom: nothing
Petal Fall: Surround + Grandevo
PF+7: Surround plus Pyganic
PF+14: Surround plus Venerate

I used to use Entrust, but PS is not on the label and it isn't very effective and its $$. As well, I like to save it for other pests its more effective against. Not that these others are inexpensive. The 309 DD period can last anywhere from 10-21 days (it all depends on DD accumulation rate each year), after which PC magically vanish from the orchard - or move to another variety that is not at PF. I like the above approach because though Grandevo can reduce pollinator activity, it is generally considered low toxicity. Whereas Pyganic kills everything (maybe not 100%, but it isn't an insect class specific material like Grandevo for example). And then venerate just to keep the material diversity high.

The one thing I haven't tried but will next year is the above plus the use of better deterrents like garlic, comfrey, thymegard, etc. I don't have the option of using chickens, but these are far and away the best way to keep PC damage at a low rumble, reduce spray costs, and feed the chickens. The bottom line is that you have be proactive (deter/distract) and can't let your foot off the pedal. Any let down in coverage is sure to be seen as a portal of opportunity for the PC.

And then there are PC peppers - but that's whole other world of Magick.

Mike Biltonen, Know Your Roots
Zone 5b in New York

Thanks so much for your inputs, Alan and Mike. Just the kind of info I need as I'm by myself on this journey into trying to grow organic tree fruit. This site has helped us at The Victory Garden orchard so much along with Michaels books and videos.
Mike, your spray strategy sounds great, and I will do that next year for sure. I also like the idea of trying a garlic, comfrey tea added to the mix, but I don't know what thymegard is and what it's for? Also, on the first Surround application at pink, are you thinking 2-3 coats at that time? And I've got to know about these PC peppers, I'll try anything to keep these ugly creatures at bay!
So I'm very new to this, just 1 year of experience since I was at Michaels orchard class. There's a lot to know, and one thing I learned about was NEWA, and we have a station one town over from us. I was pretty tuned into it all spring but when I saw it get to 309DD's and checked the orchard and found no bites yet, I thought I'm good. Next time I checked it's 343DD....game over!! Lesson learned, next year I strictly go by that. Thanks again for your help, much appreciated.

Re: Details of Grandevo application:

I'd be curious of some of the folks posting re: Grandevo effectiveness could let us know if they monitor their water pH and water hardness during the Grandevo spray mix. I remember reading in the specs that it listed pH and water hardness as an important factor in effectiveness. I wasn't sure if the recommended instructions for adjusting for hard water -- basically adding AMS (ammonium sulfate) -- would effect the basic holistic recipe and/or Surround sprays. Or even if my "crop/variety is compatible with these AMS levels." For oragnic production, they recommend an approved water conditioner...which not sure what that would be, and/or how much one more product would cost for a home grower. In general, I think we are keen to target PC given its the primary pest for our apples and peaches. But sometimes it feels like "there's a hole in the bucket" situation.

From the spec sheet:

"pH
To maintain product properties, the pH of the mixed spray solution should be between 6-8, with the most desirable level being neutral."

"If you know or suspect you have hard water, add ammonium sulfate (AMS) at levels of 1-2% (w/w) or 8.5 to 17 pounds per 100 gallons of water to help maintain efficacy. Add AMS together with GRANDEVO CG or add it to the water and thoroughly dissolve before adding GRANDEVO CG. Conduct a spray test to determine if your crop/variety is compatible with these AMS levels before adding GRANDEVO CG to the tank for spraying. For organic production, use an approved water conditioner to address suspected hard water."

Another Q. on spray details: When I talked to a company rep, he also recommended a specific sticker spray add in -- and I just mentally nodded my head, assuming the dish soap and neem would act as this. However, without a strong background in agricultural sticker/spreaders/adjuvants, I was of course just leaning towards the best and laziest solution I could imagine. So I'm curious what you pro's use in this regard.

From the spec sheet:

"Adjuvants/Carrier Volume
Avoid carrier volumes and/or adjuvants alone or in combinations that result in spray runoff or a drip accumulation. Some adjuvants have been shown to increase or decrease the effectiveness of GRANDEVO CG. Use of a quality adjuvant or crop oil is highly recommended."

Earthworks
Zone 7a in West-Central MD
Non-commercial, ~100 fruit trees, dwarf to MM106

I am not an expert on Grandevo, or spray adjuvants and water hardness, but for what it's worth:

[*] We do monitor pH and try to maintain between 6-8
[*] We have hard water, but have not attempted to use a water conditioner
[*] I think Marrone reps have recommended using Nufilm as a spreader-sticker with Grandevo+Surround. We do use Nu-film with all of our insect control sprays during the summer. However we have not used it with Grandevo because the Nufilm label explicitly says you should not spray it within 10 days of JMS Stylet oil and we do use oil in the post-bloom period for CAR control (with Regalia) and for thinning.

Does Grandevo work? I don't know. We have always had pretty low levels of PC damage, but enough to worry me that I have no idea what we would do if the damage got worse... We have used Surround for many years. 2022 is our 3rd year using Grandevo with the Surround. I honestly cannot say that I have noticed a large difference from the Grandevo.

I have always wondered as well about the possibilities of controlling PC at other stages in its life cycle. I think soil-dwelling parasitic nematodes have been mentioned in this thread. I also wonder about killing adults during their summer fruit-feeding phase. We spray beetleGONE in summer for Japanese Beetle. On the label, beetleGONE is said to be effective against insects in the weevil family as a stomach poison. Will PC adults in mid-late summer get killed by beetleGONE? What about Venerate (or Grandevo) during that period? Marrone claims that Venerate is effective vs leafrollers and apple maggot... if you spray Venerate for those purposes in late July/August, are you also controlling PC to some extent?

Chris McGuire
Southwest WI, zone 5A

Not sure if I was the one who nudged many into trying Grandevo for PC, but I think so.
As I said in my original post, we've always had quite a few PC, tried Surround with minimal success, and just lived with using PC as our natural thinnners. Scarred, but unaffected fruit, could always be used for cider anyway.
But the "final straw" was several years seeing damage to the emerging leaves before bloom. Haven't heard that from anyone else, but the buggers were definitely at it.
Seeing that last year I sprayed 25# Surround and 2# Grandevo at that very early stage early pink, and then again at early petal fall. They were gone! None to be seen.
I think nufilm would generally be a detriment to the effectiveness of Surround because Surround needs to rub off and irritate the pest. It's not simply a barrier.
I continued with Grandevo sprays as it has effectiveness against many other pests which can pose a problem. It was somewhat a shotgun approach, because so often the timing has to be perfect to be ingested after hatch and before entry into the fruit.
Michael and others say Marrone suggests Grandevo plus Surround, but I have yet to read that anywhere. Not sure why that would be so, given how Grandevo works and that it would preclude one from keeping it in place a little longer with nufilm.

Thanks for the report. We have sprayed Grandevo 4x in both of the last 2 years, 2 lbs per acre and still see some PC damage, on a broadly similar level to what we have always seen.

Marrone's recommendation for Surround+Grandevo is here:
[marronebio.com]

I was told that the reason to combine Grandevo with Surround is that the PC gets covered with Surround and then grooms itself and in the process ingests some of the Grandevo which is mixed with the Surround. Not sure if that is true or makes sense.

Another reason might be that the Surround delays ovipositioning and gives the insect more of a chance to contact a lethal dose of Grandevo before it lays too many eggs.

Chris McGuire
Southwest WI, zone 5A

Very interesting stuff! Thanks to all who have posted here recently, and especially Chris for the latest Surround + Grandevo insights. Gives us, and I'm sure others, much food for thought for future attempts at curculio control. We stopped using Surround years ago for various reasons, but will definitely consider applying it briefly and early in the future if we stick with Grandevo going forward. Much obliged.

Kordick Family Farm
Westfield, NC
Zone 7a

PS: In previous years we applied Venerate exclusively for plum curculio control at 2.5 quarts per acre, always in the weeks surrounding petal fall, and never felt like we saw a difference in pressure or damage. I see the label now reads 2-4 qts per acre. I seem to remember a much wider range on the label in past years, more like 1-4 qts per acre, so they may have updated it. Anyway, it's expensive stuff, and we always applied something of an intermediate rate and hoped for the best. I've also wondered about later season control of newly hatched adults outside of the normal target window. On the one hand, the fact that Venerate and Grandevo also act against other pests is appealing to justify their use in the event of less than stellar curculio control; on the other hand, it's pretty rare that we spray for any pests in summer proper. Also, it seems like you'd have to be doing some pretty serious monitoring to determine when the new generation of curculio have emerged from the soil and are walking around in numbers sufficient to think about ground application (I'd have to review curculio habits and life cycle, but don't believe they're hanging out in trees post emergence . . . which may preclude addition of Surround unless you're into an expensive faux snow look on your orchard floor!).

Kordick Family Farm
Westfield, NC
Zone 7a

Regarding PC adults in summer, they do feed on the fruit, in the trees, according to the references I have seen. For example https://learningstore.extension.wisc.edu/products/plum-curculio-p1889. They leave small holes in the fruit, a few mm wide. Gus Howitt's book says that the adults emerge about 50-55 days after eggs are laid in spring, which typically works out to mid/late July to early August in our climate. That's my rationale for thinking that late summer sprays might have some effect.

Chris McGuire
Southwest WI, zone 5A

I'm glad you pointed out that plum curculio continue inhabiting and feeding in fruit trees after oviposition and traditional control time is passed. I guess it's been a long time since I revisited actual literature on curculio, and did not remember that. After your post, I worked out that the next generation of adults should have started emerging in our orchard two weeks or so ago. We are in the midst of picking our 'Early Harvest' June apples right now, and I have noticed several curculio adults on the fruit, though I have not been able to assign specific damage to them so far. So it does appear that we have a viable second chance at curculio control within the growing season. Somebody had better tell the pest modelling folks at NEWA. According to our NEWA site, linked to our on-site weather station, adults are "inactive" and "plum curculio control sprays are no longer necessary." I'd love to try something new against curculio and be a guinea pig, but frankly, we are already way over budget for our spray plan and just overwhelmed with other orchard everything right now. As mentioned in a previous post, there's not really anything else we're generally targeting insect-wise in the orchard right now anyway, but if we do happen to have anything come up or have an unexpected high catch in our codling moth/Oriental fruit moth traps and decide to spray, we will definitely select something that might be active against curculio, as well.

Kordick Family Farm
Westfield, NC
Zone 7a



Edited 1 time(s). Last edit at 06/25/2022 01:28PM by Brittany Kordick.

So, when I was at Michael's orchard coarse last June, he thought that possibly the runoff from spraying Grandevo could affect the life cycle of this miserable pest because they pupate in the ground after they destroy the fruit. Then they emerge from the ground to eat more in late August - September. I'm doing a heavy ground spray tomorrow (IMO, compost tea) before a good rain and I'm going to add Grandevo to the mix and see what happens. Hoping it might cut down on next year's misery. Anyone think It'll help?

Who knows?
I think we are just beginning to really grasp the "New Worlds" out there--like we are on those three tiny ships departing Spain half a millenia ago, totally unaware of what is over the horizon.
Take a look at where the active ingredient in Grandevo came from: [www3.epa.gov]
Under some hemlock trees in MD. Is it endemic, or could (or should) it be made to be endemic? That's somewhat your (and Michael's) basic question here.
This brings up another even larger question and a tiny glimpse on that new world, or at least our knowledge of it is new. I stumbled upon this article when trying to think through what's going on with Marsonina leaf blotch in my orchard. I was thinking about what I've seen in our area over the 50+- years I've been farming and orcharding. Many small orchards and even "wild" apples seem to have disappeared. Is changing climate the culprit. That led me to wonder what is the historical geographical range of Malus. A little googling seemed to say domesticated apples took the route from Central Asia, then to the Caucasus, and to Europe. It definitely didn’t include the sub-tropics.
Are there known warmer climate varieties? This article spiked some Phillipsian musings after stumbling upon the following article.

Evidence for host–microbiome co‐evolution in apple - Abdelfattah - 2022 - New Phytologist - Wiley Online Library [nph.onlinelibrary.wiley.com]

Are there ways we can spike the biological symbiosis to help the situation, thus “adapting” Malus to a warmer climate and its attendant diseases (and pests)? And again, should we? After all, many of these blocks to our efforts are the result of human efforts or stumblings themselves. Think of all the diseases and pests from all over the globe which originated by human transmission--from the chestnut blight to Covid-19.

This year has been a weird one. Lots of "anomalies" in terms of insect and disease pests being more prevalent, more virulent, and out for earlier/longer periods of time than "normal." That without a significant increase in resilience of the trees. Can we help trees adapt to changing conditions? I think the answer is an absolute, yes. The best question is how and something I've been thinking a lot about. In Michael's book "Mycorrhizal Planet" he speaks towards this very subject in some detail. That said, in the 5 years since the book has been published I believe that conditions even more dramatically and we have to move even more aggressively in the direction of "helping" the trees become more resilient by really working on the quality and life of the soil, mycorrhizal connections, SAR/ISR systems, broader use of plant medicines for plants (a lot to learn from herbalists in this realm), microbial inoculants, etc. and fewer allopathic remedies. It will take time for sure to shift the plant's physiology from whatever it is right now to what it can be. The use of gene priming principles and practices will help the tree better adapt. In some sense we need to stop coddling the trees (e.g., a little stress is good, a lot not so much) and allowing for its own pathways to kick in and create the phytochemical composition that works best for it. I've learned a lot this year about different levels of susceptibilities of numerous varieties to common diseases and insects when sprayed under the same program. For example, Grandevo (I propose) works better in concert with a variety less susceptible to PC than another. It may also affect the development of PC in the soil. But if that were the case then we would see a general reduction in damage across all varieties. When we see differing levels of damage between varieties then I have to assume there is also something with that variety that either makes it less attractive to PC or more simply more resistant to attack (e.g., production of certain phytochemicals that help it fend off all but the initial attack). We talk a lot about the microbial activity in the soil, but rarely talk about what happens inside the plant. A Rutgers University researcher has shown that some plants will symbiotically harbor certain bacteria inside the plant cytoplasm as a way to protect it and benefit from its association. How many of these association 'inside the plant' are we not aware of? This is new territory for me, but a rabbit hole I plan to go down once the season dies down. Anyway, I there is plenty we can do to help plants adapt better to changing conditions. we just need to further our own perception and sensibilities to somewhat forecast where we're headed and to reduce our reliance on "established" practices.

Mike Biltonen, Know Your Roots
Zone 5b in New York

Alas, I tried Grandevo without Surround this year with poor results. Tons of egg laying scars, followed by far too many August feeding holes in the fruit. Way more than in the past with Surround alone.
I will be sure to rely primarily on Surround in the future!

Hemlock Grove Farm
Zone 5 in New York

Hey Brian,
What was the actual program (rates, timing, etc.) you used?

Mike Biltonen, Know Your Roots
Zone 5b in New York

2022 PC sprays:
Our petal fall was 5/17 for most vars. That day I applied Surround @ 25#/100 (~50#/A)
5/24--25# Surround + 1.25# Grandevo per 100
5/31--1.25# Grandevo per 100
6/7--half or orchard as 5/24, half as 5/31 very windy, marginal coverage
6/13--1.25# Grandevo per 100

So, I skipped Surround on about half of the 6 sprays, in the latter half of the PC onslaught. We were able to hand thin off much of the spring damage, but got hit pretty hard with adult feeding in August.

Hemlock Grove Farm
Zone 5 in New York

Interesting. The science tells us that we only need to treat for PC for 309 DD50 post-PF. The Ithaca NEWA station says there was 355 DD50 from 5/17 to 6/13. So you should have been covered. But it sounds like the majority of the damage you incurred was from the August emergence. Do you know if the summer or spring population did more overall damage, were they about the same? This midsummer emergence is a newer phenomenon that we've never really tracked (from an IPM standpoint). We know there is a second emergence, but its never been a real concern. As well, however, there is some evidence (anecdotal though it may be) that the spring emergence is either starting earlier or ending later, or both, with real impacts. This coming year I plan on trapping PC adults starting at tight cluster and ending at maybe 400 DD50, then again in August (not sure on timing). There's a part of me that thinks this is related to climate changes, not material effectiveness per se. In other words, our controls are not being applied early enough or for a long enough period or during the summer emergence, all because PC is in the orchards longer. That's my theory anyway. That said, I do like some variety in the sprays. This year I used Surround plus Grandevo, Venerate, or PyGanic this year with pretty good success including the summer emergence population. Lots to chew on here, but thanks for sharing your spray program.

Mike Biltonen, Know Your Roots
Zone 5b in New York

The science is no doubt correct when you kill PC with a stronger pesticide. When you repel them and they are still around, you need to go longer than that model. I have learned this years ago the hard way. I choose 6/20 as my end target for coverage. (I find phenology and dates to be better than degree days.)
We had more damage from spring PC egg laying. However, we were able to remove most of it via hand thinning. We could not remove the August damage that way, so it more apparent and costly. Usually, August feeding is quite minor but because we had poor spring control, I think we had a lot of in orchard reproduction.

Hemlock Grove Farm
Zone 5 in New York

I agree with Brian that the 309 b50 post-PF is not good guidance for timing the end of PC sprays for an organic grower who is not applying a lethal pesticide. My understanding without having read the original research is that timing predicts the end of PC migration into the orchard, but does not mean that all adults have died...

In SW Wisconsin with petal fall typically 5/15-5/25, we have several times seen PC adults or fresh oviposition scars in the orchard as late as 6/25 (or in one case July 12!), after the 309 b50 past petal fall.

Chris McGuire
Southwest WI, zone 5A

Guess I'm trying to see if I'm a total outlier, or if I'm missing something I might ought to be paying attention to. We've always had tons of curculio just after bloom, which I used to fret about and try to do something about. But we always seemed to have plenty of apples--but relatively few table apples and plenty for cider. But of those cider apples, most weren't damaged by curculio but by other insects. We've never thinned to any great degree either, so I considered those eliminated by curcs as just a thinning. And still, generally would have more apples than a properly thinned tree might have.
The concern I had with the curculio two years ago was that I saw them feeding on new leaves prior to bloom. I had seen that happen once before and since those leaves are so tiny, the damage can be quite severe. Thus I treated with Grandevo with good success.
I realize I risk promoting biennialism by not thinning, but the curcs? Are you all aiming for big proportion of large sized apples, thus thinning to the point where those marred or dropped by curcs become a big crop loss?

It sounds like PC may operate differently in different orchards. We have never had a noticeable issue with spring PC feeding on leaves. However, our pressure is very heavy and if not controlled, very close to 100% of the fruit would have scars in many years, with most also small and deformed. After drop, the ones left would still mostly be small and deformed.
Then comes late summer feeding by the new generation of adults. They make holes about 1/4" deep in the near-ripe fruit which then decay around the edges. Not good for fresh market.
Since 1997, we've applied Surround and been able to greatly reduce this damage. It is a bit of a bother to tank mix all the clay powder, and I was hoping that I might be able to avoid it in the future, but--not so at our farm.

Hemlock Grove Farm
Zone 5 in New York

I am hoping the science isn't situational and based on the use of toxic pesticides, but rather based on biology. Nor do I think the science is settled - I always pause when anyone says the science is settled because scientific findings should be open to new interpretations and better data especially in the face of climate change. That said, we do have different situations - the conventional/commercial arm and the organic/holistic arm, and those in between. If the science is based on the use of toxic pesticides, then we need to reinvestigate the biology under holistic circumstances. I know that Tracy Lesky and Jamie Pinero have been doing some other work re: what attracts PC to apples - so different level biology. I don't think anyone at Cornell is going down that path. Anyway, lots to learn and, Brian you are right, there are many different management situations depending on the specific site circumstances and environment, as well.

Mike Biltonen, Know Your Roots
Zone 5b in New York