My avocado plant is around 13 feet tall and is around 100 years old – my Grandmother started it. In the move from Montreal to Toronto about a month ago, it was put in storage for a few days and was exposed to cold. Its leaves have all fallen off and it smells bad – kind of rubbery (unpleasant!). The bark seems to be peeling and there is brown gummy liquid that oozes out of the bark. Can the plant be saved?
You have a couple of problems here. The first is that cold/frost damage has stressed the plant and caused the leaves to wither and drop. Branches may also die back and the bark can split from cold. But it is possible that the plant would recover and send out new growth once it’s in a stable, warm home environment.
Unfortunately the avocado seems to be afflicted with a more widespread disease as well, and it may not be able to recover. This could be some sort of canker rot or black streak, for example, although it is not possible to tell for sure. Whatever is affecting the plant likely has been present for some time, and did not just appear after the “cold storage”, although this environment probably weakened the plant.
Canker rot (e.g., from Phytophthora canker) appears at the base of older plants, starting at or below ground level. The canker is a dark area with a red, gummy exudate that, when it dries, looks like white crystals. If you look under the canker, you would see an orange-to-brown area instead of healthy whitish coloured tissue. When exposed, the lesion smells fruity. Canker rot thrives when the soil is too wet or there is poor drainage. If detected early, the canker may be controlled by cutting out the affected tissue. Your plant is severely affected – and is likely not treatable.
On the other hand, avocado black streak is also a possibility, although these cankers should look like black blotches with distinct edges; they can ooze sap that dries as a brown or white powder. Your photos show mainly oozing material, which looks almost like dark molasses – I don’t see any canker-like lesions, but then again bark that has cankers may have cracks that ooze sap. Black streak occurs when the plant is stressed, e.g., where it has not been watered enough. The plant can decline gradually or may die quickly. This disease appears not to be as severe as canker rot, and watering the plant appropriately and fertilizing it may help the plant heal to some degree.
The UC Davis’ Problem diagnosis for avocado provides an overview of diseases/pests that can attack the plant. Clearly, avocado trees grow outdoors in California, but the same issues would apply with your plant.
See also a couple of articles from the UC Integrated pest management program:
I have a feeling that this is a continuation of a question you asked us earlier this month, see Avocado tree. I agree with our earlier response that it appears to be too late to save the plant. You may want to follow the suggestions in that response, to verify that this is correct – e.g., get rid of any mushy bits and to dig down to see if any of the roots appear to be unaffected.
Although your avocado has several strikes against it – no leaves, exposure to cold weather and a serious disease – as you are so attached to this plant, which has such a lovely history in your family – you may want to contact your local nursery to see if anyone can help (show them the photos). And Landscape Ontario has links to several arborists/tree specialists around the province. You might want to try calling some of these experts – you never know, although arborists usually deal with trees that are outdoors, you may find one with an interest in avocado trees.
Please write again to tell us what happened with your plant!