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What's happened to my avocado tree?


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It's a year odd old and was coming on great, new growth etc, then about 3-4 weeks ago it started to drop it's leaves and get sick. Not sure if that grey colour creeping up the limbs has anything to do with it. I do tend to over water. Thanks.

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Your admitted tendency to overwater may be the key piece of information. Search "phytophthora root rot in avocados"

This is the most common disease of avocado trees worldwide. It is a fungus-like pathogen called a "water-mold'. It loves over-wet conditions for infection. When the infection advances it can creep up the stem and cause tissue necrosis and discoloration that you see. 

 

Start over. Or if your tree is young enough and there is enough healthy root and stem tissue intact, you may be able to save it, but you must improve the growing conditions and soil fertility (it looks pathetically nutrient deficient, which equals increased susceptibility to disease), get the watering right and clear the competitive grasses.  I suggest to dig it up and plant it higher, on a slight mound, to get the root crown high and dry and avoid water standing at the base of the tree trunk.

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By the way; I would not take samples to a Thai ag shop, unless its in an avocado growing region, they will not be likely to know this condition and they will want to sell you an inappropriate fungicide. Most fungicides will not control a watermold.  The best remedy is to make the corrections that I have recommended. But there are two systemic chemical fungicides that I know of that are specific for phytophthora,  Subdue Maxx is the brand in the US that would be most effective, as a soil drench for root uptake, and there are generics with the active ingredient 'mefanoxam'. I have not seen it in Thailand.  It would not be appropriate for a fruiting tree, but during the non-fruiting stage it may be useful if you can get it. It's expensive.  I just paid US$200 for a quart. Go with the cultural and management improvements.

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Phosphite fungicide is also useful. Agri-fos (Agrichem from Australia) (Phosphorous acid, not phosphoric acid) But this is a preventive, for building resistance, and is not a curative fungicide. 

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14 hours ago, drtreelove said:

Phosphite fungicide is also useful. Agri-fos (Agrichem from Australia) (Phosphorous acid, not phosphoric acid) But this is a preventive, for building resistance, and is not a curative fungicide. 

Thank you very much. Great advice and I welcome it. 

I went to the local nursery and the lady there said to spread a lot of cow dung around the base.

I did dig all the grass out around the tree, and left the hollow, so that probably started the trouble. I'll try and move it and put it in a concrete ring and mound it up. After reading about the root rot. Thanks again. 🙂

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If I were you I would be getting the grass back away from the trunk for starters, and loosed the top soil around the trunk a little, if you want to mulch around it, keep that back from the trunk as well.

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It happened to my tree. I found that there was a bug that had entered into the branch somewhere. So I kept cutting back, until I got to clean wood. Now I am hoping that it will reshoot on what's left. 

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I have had a similar white fungus on other plants - a local advised using a dish detergent and water in a sprayer - that cleaned it up quickly...the local said this is a dry season issue and not seen in rainy/ low season.  I left the detergent on the plant and then watered the following day...most of the fungus came off with the watering...My plants (4 infected) looked worse for a week and then recovered strongly.

 

Good luck

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23 hours ago, drtreelove said:

By the way; I would not take samples to a Thai ag shop, unless its in an avocado growing region, they will not be likely to know this condition and they will want to sell you an inappropriate fungicide. Most fungicides will not control a watermold.  The best remedy is to make the corrections that I have recommended. But there are two systemic chemical fungicides that I know of that are specific for phytophthora,  Subdue Maxx is the brand in the US that would be most effective, as a soil drench for root uptake, and there are generics with the active ingredient 'mefanoxam'. I have not seen it in Thailand.  It would not be appropriate for a fruiting tree, but during the non-fruiting stage it may be useful if you can get it. It's expensive.  I just paid US$200 for a quart. Go with the cultural and management improvements.

They operate the same as pharmacies in Thailand 

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23 hours ago, drtreelove said:

Phosphite fungicide is also useful. Agri-fos (Agrichem from Australia) (Phosphorous acid, not phosphoric acid) But this is a preventive, for building resistance, and is not a curative fungicide. 

 

Actually it is used to cure trees. See: https://www.researchgate.net/publication/225658140_Control_of_Phytophthora_Root_Rot_of_Avocado_With_Phosphorous_Acid

 

Quote, "A twenty per cent solution of partially neutralised phosphorous acid when injected into the trunks of seven-year-old trees affected by phytophthora root rot permitted rapid recovery of trees over a 12 month period." 

 

A popular tool for injecting avocado in Australia is shown here: 

 

 

 

Available from this company: 

http://www.chemjet.com.au/how-it-works/ 

 

However, your tree is too small to inject. Normally, small trees are protected with foliar sprays but you could start off with a soil drench and a spray on the leaves. I'm using Aliette on our avocado (in Laos). (About 650 baht/kg).  

 

 

I have heard that Agri-Fos is available in Thailand. Other products available in Thailand are Aliette and metalaxyl. 

 

This paper is relatively up to date: https://www.agric.wa.gov.au/avocados/control-phytophthora-root-rot-avocado-phosphite-review

 

Note the reference to the Pegg Wheel: https://www.agric.wa.gov.au/avocados/growing-avocados-–-pegg-wheel-controlling-phytophthora-root-rot Besides planting on a mound or ridge, a thick layer of mulch is very beneficial for avocado but keep away from the trunk. Calcium also has a fungicidal effect on phytophthora, so dolomite and gypsum are recommended (usually mixed with the soil before planting).

 

By the way, a healthy avocado tree will have white roots. If roots are not white, that is a sign of a problem.  

 

 

 

 

 

 

 

 

 

 

 

 

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43 minutes ago, JungleBiker said:

 

Actually it is used to cure trees. See: https://www.researchgate.net/publication/225658140_Control_of_Phytophthora_Root_Rot_of_Avocado_With_Phosphorous_Acid

 

Quote, "A twenty per cent solution of partially neutralised phosphorous acid when injected into the trunks of seven-year-old trees affected by phytophthora root rot permitted rapid recovery of trees over a 12 month period." 

 

A popular tool for injecting avocado in Australia is shown here: 

 

 

 

Available from this company: 

http://www.chemjet.com.au/how-it-works/ 

 

However, your tree is too small to inject. Normally, small trees are protected with foliar sprays but you could start off with a soil drench and a spray on the leaves. I'm using Aliette on our avocado (in Laos). (About 650 baht/kg).  

 

 

I have heard that Agri-Fos is available in Thailand. Other products available in Thailand are Aliette and metalaxyl. 

 

This paper is relatively up to date: https://www.agric.wa.gov.au/avocados/control-phytophthora-root-rot-avocado-phosphite-review

 

Note the reference to the Pegg Wheel: https://www.agric.wa.gov.au/avocados/growing-avocados-–-pegg-wheel-controlling-phytophthora-root-rot Besides planting on a mound or ridge, a thick layer of mulch is very beneficial for avocado but keep away from the trunk. Calcium also has a fungicidal effect on phytophthora, so dolomite and gypsum are recommended (usually mixed with the soil before planting).

 

By the way, a healthy avocado tree will have white roots. If roots are not white, that is a sign of a problem.  

 

 

 

 

 

 

 

 

 

 

 

 

I wish I could believe that, but in fact there are some factors that are not discussed in the research that are practical considerations in the field. There is often a big difference in what is reported from controlled scientific research from what is actual experience in field conditions.  I have been using these materials for some years, Aliette for 30 years and the others for at least 15 years.  (I have the phosphorous acid fungicide  in my pickup right now,, used some yesterday and will use the balance today. I have 25 chemjet injectors, and other injection equipment, Aliette, Thiophanate Methyl, Mefenoxam and a range of biological fungicides and botanical insecticides. )

 

The big issues that are not presented in the paper, are that

1. Aliette and some other chemical fungicides will rapidly develop resistance by the target pathogens and become ineffective after a season or two of applications. So don't count on ongoing control with hard chemistry.  If you are growing avocados or citrus, you should know and use best management practices and preventive measures for crown rot, and not have to rely on chemical fungicides.

 

2. By the time you know that your tree has P. cinnamomi, (stem discoloration, bleeding cankers, foliar dieback) there has been a considerable amount of destruction of the growing layer and conductive tissue, throughout a major portion of the root crown and lower trunk circumference. This necrotic tissue cannot regenerate. So even if you stop the advance of the disease, there has been irreparable damage. The fungicide does not cure or regenerate this damaged tissue, no matter how much you spray or inject, it can only prevent or suppress the advance of the disease. 

 

The only reason that I can think of for why you are relying on the hard chemistry, is that you have planted in poor conditions or have not practiced best management and are now desperately trying to counter the effects of inevitable disease progression. This is the reason that I have so many customers, poor soil and water management and now a desperate attempt at cure of advanced conditions. Many advanced conditions I cannot help, I have to refuse as incurable. 

 

So by far the best approach is to get the soil and water management right from the beginning, and use biological fungicides and systemic phosphorous acid fungicide as preventive, not curative. Use Calcium and other mineral nutrients along with complete nutrition, not with isolated curative expectations. It's the complete nutrition package and balance that creates soil and plant health. Don

 

 

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13 hours ago, Outbackoz said:

If I may ask CarlYai what area of thailand are the Avo's in?? Are you near the coast at all? 

No not near the coast, near Mukdahan, NE Thailand.

As I said it was looking great, but about 3-4 weeks ago I pulled all the grass out about .5 m around the base, so this left a bit of a concave in the soil around the tree base.

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I have to say, I'm totally impressed with the prognisess & answers given to the OP's question(s). I had no idea we had such an educated and well articulated group of members.

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11 hours ago, drtreelove said:

I wish I could believe that, but in fact there are some factors that are not discussed in the research that are practical considerations in the field. There is often a big difference in what is reported from controlled scientific research from what is actual experience in field conditions.  I have been using these materials for some years, Aliette for 30 years and the others for at least 15 years.  (I have the phosphorous acid fungicide  in my pickup right now,, used some yesterday and will use the balance today. I have 25 chemjet injectors, and other injection equipment, Aliette, Thiophanate Methyl, Mefenoxam and a range of biological fungicides and botanical insecticides. )

 

The big issues that are not presented in the paper, are that

1. Aliette and some other chemical fungicides will rapidly develop resistance by the target pathogens and become ineffective after a season or two of applications. So don't count on ongoing control with hard chemistry.  If you are growing avocados or citrus, you should know and use best management practices and preventive measures for crown rot, and not have to rely on chemical fungicides.

 

2. By the time you know that your tree has P. cinnamomi, (stem discoloration, bleeding cankers, foliar dieback) there has been a considerable amount of destruction of the growing layer and conductive tissue, throughout a major portion of the root crown and lower trunk circumference. This necrotic tissue cannot regenerate. So even if you stop the advance of the disease, there has been irreparable damage. The fungicide does not cure or regenerate this damaged tissue, no matter how much you spray or inject, it can only prevent or suppress the advance of the disease. 

 

The only reason that I can think of for why you are relying on the hard chemistry, is that you have planted in poor conditions or have not practiced best management and are now desperately trying to counter the effects of inevitable disease progression. This is the reason that I have so many customers, poor soil and water management and now a desperate attempt at cure of advanced conditions. Many advanced conditions I cannot help, I have to refuse as incurable. 

 

So by far the best approach is to get the soil and water management right from the beginning, and use biological fungicides and systemic phosphorous acid fungicide as preventive, not curative. Use Calcium and other mineral nutrients along with complete nutrition, not with isolated curative expectations. It's the complete nutrition package and balance that creates soil and plant health. Don

 

 

Hands on today, not Thailand but Scotts Valley California, near San Francisco and Silicon Valley. 

 

Reliant is an American brand of phosphite systemic fungicide as being discussed here.  We are using it for treatment of native oak trees to prevent Sudden Oak Death syndrome (Phytophthora ramorum).  This is a different species of water-mold from the Phythopthora cinnamomi that causes avocado crown rot, but the symptoms are similar and the treatment has similar action against the pathogen.

 

My helper is applying the fungicide with ChemJet injectors for one tree.  The last photo is a basal bark spray with the fungicide mixed with a bark penetrating surfactant, PentraBark, for absorption through the bark into the conductive tissue of the tree for uptake and translocation. The fungicide helps builds tree resistance to disease. The white material on the soil surface is a mixed soil amendment application ready for incorporation, including oyster shell lime and ag gypsum. 

 

These are oak trees that are not infected, it is a preventive treatment.  If I were dealing with an infected tree, P. ramorum or P. cinnamomi, I would first of all not take on an advanced disease condition. Because I know from experience that it is futile when there has been extensive tissue destruction from the pathogen. But if I get called for a tree in early stage of infection, with less than 10% of the trunk circumference affected with bleeding cankers, I would recommend a two year program of repeated treatments, spring and fall. Phosphite fungicide applications,  Subdue (mefenoxam) soil drench for root uptake, Aliette fungicide foliar spray application, (but only once or twice due to resistance forming). I would also sample the soil for lab analysis of nutrient deficiencies and apply prescription amendments. And I might apply a foliar nutrient solution (foliar fertilization). 

But this is the Silicon Valley economy with high value real estate and money to keep beloved native oaks healthy. 

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14 hours ago, JungleBiker said:

 

Actually it is used to cure trees. See: https://www.researchgate.net/publication/225658140_Control_of_Phytophthora_Root_Rot_of_Avocado_With_Phosphorous_Acid

 

Quote, "A twenty per cent solution of partially neutralised phosphorous acid when injected into the trunks of seven-year-old trees affected by phytophthora root rot permitted rapid recovery of trees over a 12 month period." 

 

A popular tool for injecting avocado in Australia is shown here: 

 

 

 

Available from this company: 

http://www.chemjet.com.au/how-it-works/ 

 

However, your tree is too small to inject. Normally, small trees are protected with foliar sprays but you could start off with a soil drench and a spray on the leaves. I'm using Aliette on our avocado (in Laos). (About 650 baht/kg).  

 

 

I have heard that Agri-Fos is available in Thailand. Other products available in Thailand are Aliette and metalaxyl. 

 

This paper is relatively up to date: https://www.agric.wa.gov.au/avocados/control-phytophthora-root-rot-avocado-phosphite-review

 

Note the reference to the Pegg Wheel: https://www.agric.wa.gov.au/avocados/growing-avocados-–-pegg-wheel-controlling-phytophthora-root-rot Besides planting on a mound or ridge, a thick layer of mulch is very beneficial for avocado but keep away from the trunk. Calcium also has a fungicidal effect on phytophthora, so dolomite and gypsum are recommended (usually mixed with the soil before planting).

 

By the way, a healthy avocado tree will have white roots. If roots are not white, that is a sign of a problem.  

 

 

 

 

 

 

 

 

 

 

 

 

This Pegg Wheel concept is interesting and is a good example of a comprehensive management program, including resistant species selection. 

But there are a couple of things that I strongly disagree with.  

1. the water management suggestions are opposite of what works in my experience. Root rot of various susceptible tree species is something that I deal with frequently and have for many years. Small, frequent irrigation is what keeps roots wet and predisposes root rot. Infrequent deep irrigation allows a drying out period that interrupts the disease cycle.  My father managed citrus orchards and I witnessed from a young age the successful flood irrigation program. 10 inches of water every 10 days. Drip systems are common cause for root rot when programed for multiple waterings per week. Soil conditions and drainage has to be taken into account. But the principle is that  if you keep roots wet, certain tree species will develop root rot.  

2. Applying metalaxyl fungicide at planting will be contrary to organic growing principles and will kill off beneficial soil biology.  I would instead apply a biological fungicide that complements healthy soil life. 

My application of mefanoxam is a calculated exception to save an infected tree. It is applied around the base of the trunk for uptake by adventitious roots and not throughout the root zone. It is an effective curative systemic fungicide specific for Phytophthora infections. 

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  • 1 month later...
On 3/5/2020 at 10:30 PM, rhyddid said:

Our avocado threes are adult, tall and give us a lot of fruit, in this season when the flower start to become fruit, all the threes loose almost all the leaves


Indeed over watering its a serious issue in a tropical country, roots get easily diseases and rot.

Hi, where did you buy your trees from? I need to get some more.:)

 

My tree is recovering with new shoots and looking healthier. I washed a lot of the fungus off with soapy water and spraying weekly (nearly) with sadaow and seaweed type mixture. Mounded up the tree and not watering as much.

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  • 2 weeks later...
On 3/4/2020 at 5:33 PM, Refresh said:

I have had a similar white fungus on other plants - a local advised using a dish detergent and water in a sprayer - that cleaned it up quickly...the local said this is a dry season issue and not seen in rainy/ low season.  I left the detergent on the plant and then watered the following day...most of the fungus came off with the watering...My plants (4 infected) looked worse for a week and then recovered strongly.

 

Good luck

What percentage of dish detergent do you recommend?

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