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I have an avocado plant in my outdoors balcony. It's been growing nicely, but there are small brown dots/holes in the leaves for some time now. I don't see anything in the underside of the leaves, and up until now new, healthy looking leaves have continued to sprout, but I'm concerned that it will not stay healthy.

What does it have? What can I do?

The avocado tree from above

A closeup of the leaves

UPDATE:

It's been months since I asked this question. The avocado's leaves continue to look bad, but it continues to put out new ones. I've attached a new picture of the current state as well as the trunk, in case the brown things on the trunk aren't harmless or natural (I hadn't noticed them before, because I was preoccupied with the leaves)

another close up of the leaves

This is the trunk, April 2014.

The trunk

Eyal
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    Have you found a remedy for this? My tree is starting to show similar symptoms. – emsoff Jan 11 '14 at 00:17
  • No. I'm waiting to see if the newest leaves will develop it too, or if it's related to the cold snap we had. – Eyal Jan 11 '14 at 07:59

3 Answers3

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Plants live in an uneasy balance with fungus, virus and bacteria. Sometimes they coexist, sometimes one attacks the other. The symptoms I see look like a soil borne infection caused by a stress to the plant.

One possible cause for this is overwatering. Underwatering tends to produce large areas of dead tissue in the leaves which I don't see here. If you think overwatering is possible just try a drier watering regime and see if the new growth is healthy.

Edit: Eyal asks about spider mites. This answer Why are these white dots appearing on my citrus and avocado trees and the leaves getting pale? is about avocados and citrus and has more detail about identification and control

Community
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kevinskio
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It can be several things. I have to look at the back of the leaves to know for sure. My guess is:

Spider mites if there are red dots

Thrips or whiteflies if there are white dots on the back

It can be sun burn from misting if the back looks the same

user3084006
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    For indoor plants spider mites look like white grains of salt. Thrips resemble black exclamation marks. Whitefly are white or off white and move or fly readily. – kevinskio Dec 26 '13 at 14:49
  • I don't see anything on the underside, but you can look at the updated picture I've added- maybe one of you will notice something. – Eyal Dec 28 '13 at 13:26
  • @Eyal Was there cold temperatures, fog or hail? – user3084006 Jan 02 '14 at 09:50
  • Yes, there was about 5 degrees Celsius, and hail. But the avocado is somewhat protected by a roof. – Eyal Jan 02 '14 at 10:17
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    @Eyal It is likely the cold and probably the fog. The edge of some of your new leaves look like they might have had some burns too. I would actually not worry too much they do this every time it gets around 3-5C and lower. If it gets too cold below 1.6C (35F) they may drop their leaves and new stems can turn black and die. – user3084006 Jan 02 '14 at 11:01
  • @kevinsky The cold snap was a long time ago (December) and yet the problem persists. Today, for the first time, I noticed something that looks like what you called spider mites - something salt sized, white, moving on the underside of the leaves. Is rubbing the leaves with a mild dish soap solution going to do the trick? Should I remove heavily damaged leaves myself? – Eyal Apr 17 '14 at 14:36
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I’m a bit late to the game, but I found your post when researching the same issue with my avocado tree. I spoke to an arborist and he said these are not mites but rather leaf burn - your tree is not getting enough water and as a result the light is able to burn the leaves. Deep water once a week and it should prevent future burn - cut off the burnt leaves to keep the tree from wasting energy on trying to repair those and it should do much better after a few weeks.

Claire
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