ACT = Australian Capital Territory, near Canberra

Quince fruit is susceptible to brown rot, it occurs more often in humid, damp conditions. The rot can form around a small injury but most often along cracks.

The misshapen fruit was likely not pollenized evenly, a small percentage of fruit does this naturally.

Not familiar with your local insects.

How large does the fruit get on average when it falls? Is it turning color or is it totally green? Is the foliage healthy?

You may need to bag individual fruits to fend off insects.

And you can't expect a lot from a 3-year-old quince tree. If you are losing a high percentage of hundreds of fruits from a more mature tree, that is a problem.

Thanks Larry,
I'm in Canberra. I did notice some tiny little black beetles crawling around some of the fallen fruit.

Some of the fruit fell off when only the size of small lemons, but now they're very big and fill my palm, and still developing rot and falling. They're still mainly green, but I can see a feint yellow colour developing, and I can even detect the early stages of perfume from the fruit.

The foliage is generally healthy except for the skeletonised damage from the pear/cherry slug, which is rather widespread on this tree, despite my ash shower and occasional finger squashing.

I think you're right about it being Brown Rot. Is there an organic solution to this?

The misshapen fruits primarily are caused by the plum curculio. Those may also be the little beetles you see. They deform the fruit but you don't see the entry until you cut it open. So, I think you have a bad curculio problem. You should check to see if this bug is a problem in Australia, I expect its found its way there by now but maybe not.

The frass holes are usually caused by codling moth. Quince don't get brown rot badly if they are not bug infested, but the bugs make holes which let diseases in.

The primary organic control for the bug problems is Surround, it is kaolin clay. Here in the states its sold as Surround WP, not sure about down under.

Scott

Thanks Scott,

I'll scout around for Surround or its equivalent. I did once notice a single grey beetle, but not near the tree, so I thought nothing of it. The beetles I saw crawling around on the fallen fruit were much smaller - only about 2mm in length - and shiny black. But they may have just been ground scavengers along with the slugs, and unrelated to the problem.

If I need to treat for brown rot too, what's the organic solution?

I'm wondering if it's worth it for a couple of bowls of fruit once a year...

Thanks

I never saw any brown rot on my undamaged quince. The best organic brown rot spray is probably sulphur; its not super effective so regular sprays are needed, in particular it needs to go on before rain with a sticker.

Just be lucky you don't have fireblight or quince rust yet, those are the real deal-breakers. My quince were turned into firewood several years ago.

Scott

My quince brown rot takes about 5% of the crop, so I've never checked into it. Just looked at your photos and they look like the typical array of quince problems.

Any chance a bird is pecking at some fruits? Humidity or rain cracks usually start at stem or blossom end and run longitudinally.