I'm co-maintaining a small orchard. Often, noone will look after it for a while. Nature conservation and tree/ecosystem health is more important for the group of maintainers than a high yield.

After and during harvest season, there are naturally a lot of apples on the ground, mostly windfall, I guess, maybe a few from shaking and not collecting. Many of them are good to eat, but still a lot aren't collected by anyone and just rot. I'm wondering whether that's good or bad. Should we leave the rotten apples on the grass, or should we remove them?

Pro leaving: The apples contain the nutrients the tree will need in the next season. Leave them there to let the tree reabsorb them.

Pro removing: The apples will attract all sorts of bugs and possibly illnesses (bacteria, funghi) that are harmful for the apple tree. Remove them, compost them, and apply the compost after 2-3 years.

  • Apples are acidic. Do you want acid soil in your orchard? – Peter Bill Feb 23 at 10:45
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    As an anecdote, I was asked to clean up under my single apple tree one year, because it attracted deer and the deer were being followed by a mountain lion. Normally the mountain lion would not follow deer into town, but the drought had driven pretty much all the deer into town. – Michael Richardson Feb 23 at 15:23
  • If you mow grass under the trees , the fallen apples are messy in the mower blades. – blacksmith37 Feb 25 at 15:42

According to this publication from the University of Wisconsin Extension, the larvae of several destructive insects can grow to maturity in windfallen apples:

  • Apple Maggot Flies (pp. 12, 14)
  • Codling Moth (p. 15)
  • Plum Curculio (p. 16)

In all three cases, you should remove all windfalls but not compost them (it's recommended that you bury the apples at least two feet deep instead).

The University of Minnesota Extension agrees with these recommendations, in these pages: Apple Maggots in the Home Orchard, Codling Moths in the Home Orchard, and Growing Apples in the Home Garden, which also mentions Apple Curculio. The one difference between UW and UM is that the UM pages recommend putting the apples in your municipal trash rather than burying them.

So, in answer to your question, if you're in an area where any of these four pests are present, it is definitely a good idea to remove windfall apples throughout the growing season in order to prevent pest problems the following year.

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    Birds don't need to be "provided a bonanza". All this does is breed insects, +1 – Mazura Feb 23 at 1:20
  • @Mazura - posted under the wrong answer? – Jurp Feb 23 at 4:27
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    @Jurp, I believe Mazura was agreeing with your point about insects, while suggesting Peter's answer isn't helpful because birds don't need to be "provided a bonanza." – Kirk Woll Feb 23 at 16:18

Here in the UK fallen apples are eaten by several species of birds. Here's a quote from this link:

The bumper crop of apples nationwide in 2013, and the fact that they stayed on the trees so late in many instances, seems to have provided a bonanza for native and migrant thrushes. The pictured birds below - Blackbird female, Redwing and Fieldfare - were among a group of around two dozen feasting on windfalls this morning. A Song Thrush was also present, but not interested in the fruit, while for the first time in my experience a Great-spotted Woodpecker also seemed to have a go at an apple for a short while. Fieldfares appear to be top of the pecking order, no doubt because they are the biggest of these garden visitors. One devoted the best part of 20 minutes trying to chase away Redwings and Blackbirds, an exercise in futility given the number of apples available across a fair-sized area in the garden.

So if conservation is your aim, leave them for the birds.

  • That's definitely a good point, and we also leave plenty of apples on the tree. However, they are so many that they still start to to rot before the birds can eat them. So I'm still wondering whether the mouldy rotten ones should be removed after the birds had their feast. – Turion Feb 22 at 13:15
  • Also, the birds might eat the apples from a compost heap just as well, I guess? – Turion Feb 22 at 13:15
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    As they decompose, they also ferment. That can have good and bad side effects. Inebriated birds trying to fly can be quite amusing to watch. Hedgehogs can get into alcohol-fueled territory fights as well. But over aggressive drunken wasps aren't so nice to have around... – alephzero Feb 22 at 16:28
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    @alephzero - "Hedgehogs can get into alcohol-fueled territory fights" is a marvellous sentence – lupe Feb 23 at 19:50
  • "Hedgehogs getting into alcohol-fueled territory fights" - isn't that a new show on BBC2 this autumn? – Jurp Feb 23 at 20:14

No, any Brown Rot (Monilinia fructigena) will breed on the fallen fruit and affect the next years apples and stone fruit.

If present in your area, the Mediterranean or Queensland fruit flies will breed there.

The wikipedia article is a bit boring, the other ref. is more readable.



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