Excessive Codling Moth Damage – Reduced Harvests Ahead?
I’ve got a bit of a bad feeling about the prospects for this year’s garden / allotment / small orchard apple harvest here in the UK, and it’s largely this little so-and-so’s fault:
That’s the larvae of the codling moth, seen here shortly after it had emerged from an apple and was attempting to make a getaway1Spoiler: it didn’t make it… in order to hibernate and pupate in the leaf litter around the base of the tree it came from, to emerge the following spring as an adult moth, lay more eggs on apple leaves and start its life cycle all over again.
This year I’m seeing a lot of codling moth damage on the apples on my allotment, and in the orchards at work. It’s a rough estimate rather than a scientific survey, but I think I might be looking at damage-rates of between 80% and 90% of the crop this year, although some of those fruits will hopefully be salvageable for cooking with. Bearing in mind that the majority of my allotment trees are small cordons, which only carry a dozen apples at most in a good year, that could mean I only get to pick one or two, maybe three decent apples per tree this year. But in many cases there will be no undamaged apples on a particular tree, and overall, I know I’m going to have very few apples that are worth keeping into winter.
Here’s an example of what a codling moth larvae typically does to the outside of apple:
And here’s an example of internal damage, on a different apple:
Not a pretty sight, is it? The larvae tunnels into the centre of the fruit, and then usually chomps its way around the core before tunnelling back out again. Although it’s unlikely to eat the whole apple, it will leave a lot of frass (droppings) behind, making for an extremely unpleasant eating experience, if you’ve not noticed an entry and/or exit-hole and haven’t prepared accordingly.
According to the NIAB website codling moths really enjoy just the sort of hot, dry summer we’ve been having here in the UK, all through their peak season of activity:
“[Codling moth] adults fly at and after dusk on warm evenings at temperatures >15 degrees C.”
We’ve been having plenty of those over the past couple of months, so the adult moths are likely to have been moving around from tree to tree quite freely.
The problems aren’t limited to the actual larvae-damage alone. If a tunnelled-into apple is left on the tree, there’s also a very good chance that brown rot spores will get into any holes that have been made by the tunneling larvae, and quickly spread to infect the whole fruit, rendering it completely inedible:
The brown-rot-infected fruits will also infect the fruits next to them, if they’re touching, so if you haven’t made time to thin out your apples earlier in the year then you can easily lose whole clusters of fruit at once.
The one bit of good news is that if you catch the damage early enough, you can chop out all the affected parts, wash the remaining apple, and then either eat it raw – if it’s reached a reasonable state of ripeness – or, even better, cook it into a stewed apple purée, or spiced apple compote (yum!)
Codling moth is a tricky pest to deal with, because it’s extremely difficult to effectively control it on a small scale, and in a bad year (for us, or a good year for them) the larvae of the moth can do massive amounts of damage in an orchard. On an agricultural scale there are various viruses, insecticides and pheromone controls that might be used, but these products won’t be available to the small-scale grower. And if, like me, you prefer to grow as organically as possible, then you’re left with orchard hygiene – picking up and disposing of infected fruit and clearing leaf litter from the base of the trees in autumn – or trying to catch the larvae as they hatch, but before they reach the fruit, which would surely be an almost impossibly lucky occurrence.
A word on codling moth traps, which are available from Amazon and other online retailers: they do catch some of the male population of codling moths during mating season, which can reduce the numbers of mating adults, slightly. But they’re not comprehensively effective – they won’t catch all the males before they mate, and they do lose their efficacy over time, allowing more males to escape the lure – so they’re really intended as a monitoring system, an indication that the population is peaking, to signal when other control measures should be taken. Which, as I’ve mentioned, are few and far between for small-scale growers. By all means give them a go if you only have one or two trees to try to protect, they might help reduce the proportion of infected fruits, but they’re probably not all that useful at any sort of scale, especially if you have neighbours with un-trapped apple trees, from which a population of moths could develop, and then reinfest your trees at a later date, in the second breeding cycle. I don’t use them myself, for that reason alone.
This summer the additional threat posed by pests of the feathered and furry kind has ramped up again as well, with the hot, dry weather causing more critters – pigeons at the plot, parakeets and jays at work, squirrels pretty much everywhere – to attack the fruit, perhaps seeking the moisture they can’t find elsewhere at the moment. And of course, they make much larger wounds than moth larvae, leading to more surface area for brown rot spores to infest.
All of the above has plenty of echoes of summer 2021, when I bemoaned the impact of Mother-loving Moths and Bastard Bloody Pigeons. Back then, I seemed to be pretty stoic about the situation, which seems like a reasonable stance to take, so I think I’ll just quote myself and leave you with this thought:
“All I can really do is take solace in the fact that last year was an excellent year for apples, even allowing for the fruit we lost to the same pest problems. This year overall fruit set is down (for perfectly natural reasons), so the fruit we’re losing represents a higher proportion of the total crop, which is why it’s so annoying, but that doesn’t mean that next year won’t be another great one.”
2021 Me seemed to be talking sense, so I’ll do my best to follow his advice again this year.
How about you? Are your apple crops badly affected as well? I’ve had a couple of emails from readers saying they’re looking at similar levels of infestation to me, but I’ve also spoken to an orchardist friend of mine who says their trees down in Suffolk are largely codlin-free. Do let me know how badly affected your trees are, and especially if you know of, and particularly if you use, any effective control methods, via the comments.
Footnotes
- 1Spoiler: it didn’t make it… ↩︎
Hi Darren
Very similar down here in South Wales on Gower. We had quite a good fruit set, a bit of a surprise after the fruit-tastic 2025, but our orchard has taken a hit from the Codling moths and lots of blackbirds that have gone for the fruit in the trees rather than on the ground. Not all trees affected equally by moth damage though most of the orchard trees had some damage. Katy apple has suffered most from the moths although still quite a bit of fruit left. Ribston Pippin and Jupiter only mildly hit and they are loaded with fruit again. Our stepovers not affected at all. Might try nematodes? Saw my first sunburned apple (Discovery) this year as well!
Best wishes, Jeremy.
Hi Jeremy – Interesting that the stepovers don’t seem to be as badly affected as some of the (I assume) larger trees. Could be variety-related, or possibly something to do with proximity? Hard to say. Nematodes are one suggested remedy, but tricky to apply, as apparently you have to time the application almost perfectly and ensure full spray coverage of all the leaf area to catch all the grubs. Might be worth a go on a smaller tree or two, to see if they make a difference.
Plenty of codling here in suburban Heaton Mersey, Stockport. I’ll make a point of removing affected fruit and clearing away the fallen fruit from the ground. Figs doing well, which is a compensation.
Hi Chris – Yes, orchard hygiene seems the best defence against a growing codlin population. Glad to hear your figs are thriving. You’d hope so, in this distinctly Mediterranean weather!
Hi Darren — one thing to add: if the chewing damage to the fruit is occurring during the day, it’s squirrels. If it’s at night, it’s rats. Nobody likes to admit to it, but rats are a significant pest in urban gardens worldwide. I remember a farmer’s market customer, a well-to-do older woman, telling me that squirrels were eating the peels of the lemons in her San Francisco rooftop garden. I asked her if the damage was happening at night, and when she replied that it was, I told her that the destruction was being caused by rats, not squirrels (plus rats love citrus peels). She was completely indignant, refused to believe it, and stomped off.
We’ve dealt with increasing codling moth issues here in Sonoma County, California for about the past decade. Nighttime minimum temperatures are increasing faster than daytime ones with climate change, lengthening the season for codling moth so that more flights happen per year. Untended trees in the hills also act as repositories for moth. They cannot be conquered without a rigorous spray regime, something we don’t do at all on our farm!
Hi Dan – Very good points, thank you. We have had a few problems with Rattus norvegicus in the past at work, and I wouldn’t be surprised if they were active in at least one of our orchards. We also have voles and mice round the place, who might not climb the trees, but will surely have a nibble on the windfalls. And yes, there are wild seedling trees out in the woods, and of course trees in other folks’ gardens nearby that serve as codling hosts. From all the Super El Nino forecasts it doesn’t sound as if next year is going to be any cooler, either. Fingers crossed we all get through it with some sort of harvest to show for our efforts!
I am crossing my fingers and toes! Next year is forecast to be warmer than this one simply by virtue of the energy released this fall and winter from the Pacific Ocean into the atmosphere during this El Niño.
We’ve had three wet winters in a row, a statistical anomaly in Northern California, and as a result the sheer number of rodents this summer is beyond anything I’ve seen. We only have a native rat, the Dusky-Footed Woodrat, which I must admit is quite cute–for a rat, anyway–but they eat anything and everything in the garden. Field mice and voles are also off the charts in numbers. Western pocket gophers, which do the most damage to the roots of our trees, are booming. Fortunately, we’ve got two barn owl nesting boxes on the property, and they clearly help us keep the rodent population down in the orchard.
Our biggest pest is deer. They use our orchard as a pass-through to get water from cisterns down the hill. If f I fixed the perimeter fence they’d end up having to walk along the highway to get to the same spot, resulting in lots of deer-automobile collisions. So I let them stay, to the detriment of the trees.
That’s very noble of you Dan, and quite right, too. We don’t have deer issues at work, thankfully, but I think we could maybe do with some more owl nesting boxes nearer to the garden to help control the rodents. And then all we have to do is work out how to stop visitors helping themselves to fruit and, allowing their kids to throw footballs into the trees…
My observations reflect yours. Bit of a disaster for me this year to be honest. I will be trying cardboard collars next year and of course orchard hygiene I the hope that I can put a dent in the numbers.
Hi Olly – Cardboard collars around the tree to give the maggots somewhere to pupate are definitely worth a try. Normally I’d say it’s too wet in our neck of the woods for them to last a season, but this year… maybe a good idea. Won’t catch the maggots that fall from the tree in an apple, but as you say, combined with hygiene practices, it should help to reduce the numbers for next season. Do please let me know how you get on.
…also, I was thinking the increase in bird damage could be explained by the fact that there is so little water about and the apples are a good source of hydration?
…yes, absolutely. Not much else around that provides moisture at the moment, so birds and mammals are probably desperate for anything that they can use to rehydrate.
Thank you for the heads up. Seen none here in the past but will act if do as sounds like they get bad if left alone
Hi Russ – If you do spot an infestation and have a chance to break the life-cycle then hopefully it won’t end up getting worse year-on-year.
Useful chat! Our Blenheim apple is mostly (90% so far) Codling-infected and only useful for cleaning up and stewing. We normally store healthy apples that last till end Feb/early March but not this year! Worcesters are less affected by moths but lots of brown rot. James Grieves are mostly pest/rot free (10% level) but tiny due to drought. Most resistant are Spartans which still look OK, although they are a late ripener. Our greengages are affected by plum moth every year but normally les than 10% of the crop. This year more like 90%. Certainly the worst year I have experienced in 40 years. Your philosophical approach – maybe better next year – the only reason why not giving up!!
Hi Mike – Those are some disheartening stats, but it sounds like the Spartans might be a bit less attractive to the moths? I’m going to see if I can dig a bit deeper into the available research, see if anyone has assessed whether codling is more prevalent on early-ripening varieties, or dessert apples rather than cookers, or if there are any definite weather-based correlations that anyone has noted. Shame about the greengages as well, one of the finest fruits in the orchard, imho. Our trees at work are having a rest year anyhow, so that might help insert a break into any pest population build-up. We’ll see what happens next year.
The point about pheromone traps being useful chiefly for monitoring, rather than a complete control, is especially helpful. On a small cordon where there may only be a dozen apples to begin with, that level of damage really does turn into almost nothing for storage. The practical emphasis on removing affected fruit and leaf litter makes a difficult season feel a little more manageable.
Thank you Aneeq.
My experience is the same as Jeremy above. Our two large, old trees have been decimated. The four stepovers are untouched. They are not that far away from each other!
I have two hypotheses:
1. The stepovers are young and have smooth bark, with no winter hiding places for the grubs. The old trees have cracked and gnarled bark, with lots of hiding places.
2. Maybe codling moths like to fly quite high above the ground, and don’t look for apples close to ground level? It’s not a natural place to look for apples!
I am planning to try a winter wash next winter. Our neighbours commented that this helped their tree.
One plum tree has had the entire crop destroyed by plum moth. The other is untouched. The bad plum tree is next to some blackthorns in our neighbour’s garden. I think this is the source.
Hi Steve – Yes, those theories sound quite sound to me. I do still have quite a bit of codlin on my 5′ – 6′ stepovers, but I’m sure they’ve flown in from some of the larger trees around our allotment site. Odd that the plum moth affected one tree and not the other. Something to do with the scent of the fruit of the one they attacked being more attractive, perhaps?
Absolute Codling carnage at our small orchard in Gloucestershire. Young and old trees all affected. This is the first year there has ever been any damage ( that I’ve noticed?), so has gone from virtually zero to a major infestation in one summer. Picking up all fallen apples and putting in bin bags to rot and bought some nematodes, so will see how it is next year. I assume it’s too late for cardboard around the trunks now? On the plus side, it was a great year for soft fruits and plums!
Hi Chris – Very sorry to hear about the codling carnage, but great to hear that the berries and plums have done well. Must have been a hell of a shock if an infestation hadn’t happened on a noticeable scale before. Of course, Gloucestershire will be packed full of orchards that are potential sources for the moths, which will have been more mobile than usual this year, so that’s probably how they reached you. Fingers crossed those nematodes work well next year. And yes, I think it will be too late for cardboard to do more than catch a few stragglers, if damaged apples have already started dropping.