Problem with our avocado fruit

brad16 says...
My first impression was a fungal disease but I'm tending to think it looks like severe sunburn.

Picture 3 is the one of interest. This one has two holes in the skin and the larger hole seems to be freshly made. The flesh inside doesn't seem to indicate brown rotting flesh that would be expected from a fungal infection like anthracnose.

How is the canopy of the tree?
Is it thin, where fruit would be exposed to direct sunlight?

Sydney has had a long, hot summer this year. I work outside, and the sun has been quite intense. Sydney usually experiences this, but normally only for a short period around the new year. This year it has lasted much longer. Your tree is in the ground and quite large, so will have a good root system to sustain it through a dry period, but maybe the extended period of intense, direct sunlight burnt it, just like it does the fair skinned European tourists down at Coogee and Bondi beaches.

If it is fungal, you have a big clean up and control job ahead of you, especially since it's a large established tree. Although I suspect it to be severe sunburn, a fungal infection will not just go away, so don't be complacent.

Have a look at the remaining fruit in the tree. If all the marks point towards where the sun shines, then that could be another good indicator for sunburn. Infections won't be so uniformly oriented. They will occur anywhere where fungus spores can gain entry (ie. cuts, bites, pores etc.).

Also fungal infections radiate out from the point of infection. Lets say anthracnose entered an avocado from a pin prick in the skin. By the time you saw a marble sized spot on the skin, there would also be a hemispherical region of rotten flesh underneath it. If that was to grow as large as the black spots in your pictures, the rotten flesh would be about half of the avocado, including the seed. This is why your 3rd picture stood out to me. The flesh underneath just didn't look to be rotting into the avocado as I would expect for a fungal disease.

The more I think about it, another indicator that points to sunburn is the approximate location on all the avocados in the washing basket. All the marks seem uniformly similar in size and orientation on the fruit. They all seem to have clean bums. They look as though if I hung them all, all the marks could be arranged to point in the one direction.

Anyway, they are my thoughts. Good luck.

Pictures - Click to enlarge
Picture: 1

Markmelb says...
Luke - a pic of the tree would be a good start for us to work this out? Looks like sunburn due to not enough leaf cover. If you can see through your tree then it has root rot issues - no different to what Avo orchardists contend with by using Phytophera fungicides on an ongoing basis. Unless of course they have perfect conditions of drainage etc but they still use preventative measures. Antirot spray can help or Metalaxyl from Elders.

Even the original Hass tree died of Phytophera - google as good story on Wiki.