How late can you hand-thin apples?

General Fruit Growing
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Weather has been unusually warm and wet in Northeast Wisconsin, and the fruit set is heavy.

I am attempting to hand thin six semi-dwarf to standard-sized trees. I have pruned them so much of the fruit is reachable from the ground, and I am not getting the ladder out to thin upper branches.

I put two days on site and I made good progress on two of the six trees, doing perfunctory thinning on the other four.

The largest fruit was about nickle-size on a Duchess of Oldenburg on which I did a reasonably thorough job. The fruit ranges from pea to dime size on a Honey Gold that didn’t bear much last year, but I am anxious to thin it some so I don’t end up with hardly any fruit in 2025. The Honey Gold is a Standard that I have pruned into a sprawling spread of bearing branches. I felt completely overwhelmed by the masses of small fruit, and a robin is nesting in one of the branches, alternating between quietly sitting on the eggs and going “Crazy Robin” flying from tree to tree loudly squawking.

How big can you let the fruit get, or how many weeks past petal drop and still hand thin?

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I hand thin throughout the season. We’ve had a lot of fruit destroyed by wasps and hornets in the previous years and tend to get windstorms, too. So doing all of the thinning in spring would end poorly. In spring I will leave about 150 -200% of what I’d like to harvest on the tree and go from there.
If you want to thin but can’t use a ladder (I’m not getting up on one either) start your thinning by shaking the tree (gently at first). That will reduce the fruit in higher up - and you will get rid of fruit that would fall off anyway first.

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To have an affect on next years crop you really need to thin within the first 30 to 40 days after petal fall. That’s when seeds start developing. The more potential seed on the tree, the more hormone there is, and the more likely it will go biennial.

But @Tana makes good points. There are a lot of ways you can lose fruit so it’s always a judgement call as to how early and how much to get rid of. The first years I would error on the side of thinning and you’ll be able to tweak what works in future years as you get to know how the trees perform on your site better.

It’s a chore though so don’t beat yourself up if you can’t always get to it.

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Ditto that for Sheboygan County except that we have the chilly lake keeping a lid on temperatures. I see a few curculio nibbles, but they are not out in full force like they will be when it dries off and warms up some. For this reason, I haven’t nuked them at sunset with Carbaryl yet this year.

I’ve trapped a codling moth here and there but am holding off declaring biofix for them, too. I suppose Hades will break loose one of these days, and I’ll be too late to do anything. The saving grace about codling-moth control is that you have an interval before egg laying begins in earnest, so you can pick a good drying, windless morning to spray for them.

I’m about half-way through manual thinning between the raindrops. Fruit set is heavy but fruitlets have yet to reach dime-size diameter. It’s a mentally agonizing job. I always think I’m wasting a crop-year by thinning so much, but then I always wind up with more than I can use. Just forcing myself to do it anyway improves tree structure and hopefully future crop loads, though.

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The University of Wisconsin Peninsular Agricultural Research Station just north of Sturgeon Bay May 31, 2024 – Peninsular Research Station (wisc.edu) is reporting trapping some codling moth as you are reporting and they are not seeing any curculio damage on cherries quite yet.

On Sunday, I sprayed my orchard south of Sturgeon Bay with what I use against these insects (Avaunt on the plums and neighboring apple trees, Assail on everything else) and against plum brown rot and apple scab on my susceptile apples (Spectracide myclobutanil).

On the topic of Assail, this year I purchased the minimum size amount of 128 ounce of 30% SG (soluble granule) formulation. Given that I am mixing batches for a 3-gallon hand-pumped sprayer, I am using what I call a “drug dealer” scale to measure out single-digit gram quantities to a tenth gram precision. Actually it is one of these cheap battery-operated digital scales for measuring small food portions for people on a diet.

Avaunt came in an 18 ounce container, and it is not too hard to “tap out” the granules into a plastic mouthwash cup for which the scale has been zeroed. Assail comes in a 128 ounce container with a bigger mouth, and this agent doesn’t tap out into the cup as cleanly. I need a better way to handle it without spilling, although I am doing the measuring and mixing out in the orchard rather than in the driveway.

In addition to a drug-dealer scale, do I need a drug-dealer spoon to scoop out gram quantities of Assail out of its container? According to the label, transfering granules to a smaller container is a big no-no for safety reasons of not knowing what you have in it, despite the best intentions to label with a Sharpie.

The fungicide goes without saying given all the rain, but the first “cover” of insecticide was in anticipation of the hot-and-humids arriving this week. Yeah, yeah and yeah IPM and all of that and don’t spray for what you haven’t scouted, but once you get the weather conditions, whammo, you are swarmed with these insects.

So tell me, what is this biofix thingie?

By the way, the apples I finished thinning and bagging “down south” in Madison are getting huge for this time of year, some of them past golf-ball size. This is in a city neighborhood that doesn’t meet the label definition of “farm” or “commercial”, even when I squint" for the agents I am using in Northeast Wisconsin.

With each every-other-day heavy rain I am getting bags dropping from the tree with dime-to-nickle size apples. So despite my best efforts of hold off on bagging in the face of curculio scars, selecting king-blossom fruitlets, no more than one bag every six inches of branch, I am still getting bags on the ground.

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I love these needle-nosed snips for thinning apples on the tree. Makes fast work of it.

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See my Phenology page and my write-up on my WeeWX weather-station software extension.

:slightly_smiling_face: That’s the sum-total of my late experience bagging apples.

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I am in Northern Waukesha county in Wisconsin. Odd that the curculios have hit one of my apple trees with a vengeance. Others at work who grow apples tell me they find no curculio signs yet on their fruit.
For some reason they sure love my LindaMac apples. Busted out the Imidan to hopefully teach them a lesson.

On the subject of apple thinning, I always heard to start in June as soon as the fruit was big enough and get done by July 4th. At least the commercial orchard I worked at years ago in Leeds, WI taught me. His comment was thinning early had the best effect on increasing the remaining apples left on the tree for size. Thinning after july 4th would help reduce any potential limb breakage from too many fruits but the ability to increase apple size went down the later one would thin after July 4.

Biofix normally pertains to coddling moths. When a specific number are trapped within a 5 day period, then the biofix date is set. This allows the grower to hopefully predict peak activity and then spray at that time. I believe it is about 12-14 days after setting biofix? Don’t quote me on that.

I just follow the midwest spray guide on the internet for spraying. But if a commercial grower can set the biofix and save a spraying or two it really saves them time and money.

I know many now use the pheromone strips commercially for coddling moth for mating disruption. I am still wondering why nobody pre-packages them into smaller quantities for home fruit growers to purchase and use? Perhaps the home fruit growing market is too small for these companies to want to deal with.

So until then, I spray away with my Imidan or Assail to keep the curculio and first generation coddling moths at bay. Both products have worked well for me.

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In commercial-scale operations, concentrated pheromone lures may be used to disrupt the mating behavior of most male codling moths, but this is effective only for isolated orchards or for orchards extending over several acres, which are not easily accessible to bred females from outside. It is definitely not as effective for the backyard gardener.