Author Topic: any tips on preventing phytophthora root rot in avocados  (Read 6328 times)

fruitnewbie

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any tips on preventing phytophthora root rot in avocados
« on: May 26, 2014, 03:08:23 AM »
Hi all,
Hope you are having a relaxing Memorial Day weekend. We just had a thunderstorm here with quite a bit of rain and it got me thinking of my young avocado trees and my attempts to prevent root rot. Some of the things that I try to do are:

1. put dolomite in planting hole and sprinkle liberally around drip line
2. plant on a mounded slope with area that drains (which is challenging as I have clay soil and get 60-80" of rain a year).
3. Agrophos foliar spray once every few months

My question is are there other things i can do? How frequently should I apply dolomite? And how often should I apply agrophos foliar? My Green Gold, Kahaluu and Ota look ok but Wurtz is struggling and looks pathetic. If you guys and gals have any "secrets of the trade" to prevent this devastating disease, please share. It would be greatly appreciated by all of us struggling to be rewarded with ONE STINKIN' AVOCADO. And if Carlos is on line, I was devastated that your Kahaluu dropped all its fruit. I was watching your progress with that one. But man it sure grows fast.

Thanks,
Jenna




jmc96

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #1 on: May 26, 2014, 04:13:36 AM »
Does agrophos contain Phosphoric acid or Phosphorus? You need to apply Phosphoric acid religiously every six weeks to keep phytophthora under control. Here it is marketed as Yates anti rot. As long as the soil is perfectly drained, it doesn't matter how much water they get. They won't tolerate standing in still water.

Mike T

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #2 on: May 26, 2014, 05:27:12 AM »
I get 100 inches of rain, I'm coastal at 17s latitude, have clay soil and wurtz, reed, shepard and hazard grow fine and never had any phytophthora. I used to use phosphonate and anti-rot when they were young but realised I didn't need to.

Dolomite is ok if you are low in Mg and have a pH below about 5.5 but in the planting hole and used regularly? Excess Ca and Mg can cause antagonisms of nutrients but I guess over use of gypsum and lime is just as bad. Drainage and a lack of puddling is important.

A mound on a slope should mean they will be fine unless there is phytophthora upslope or poor hygiene potentially spreading spores.

Mulch heavily and keep it well back from the trunk and don't fertilize excessively with strong mixes that contain chlorides close to the trunk. Chlorides and salt are bad news. Correct and micronutrient deficiencies and have good hygiene practices so you don't introduce it.10:4:6 would be a reasonable NPK.

fruitlovers

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #3 on: May 26, 2014, 06:21:40 AM »
Really the most important step was or was not taken by the person that sold you the plant: did they use a phytophtohora resistant rootstock? Some trees are very resistant and others succumb very easily. Here we use seeds for rootstock from trees that have grown for very long time and shown to be resistant.
Oscar

Mike T

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #4 on: May 26, 2014, 06:27:19 AM »
Commercially produced trees should just about always have the best rootstocks for the area. That would include the most disease resistant rootstock.

BMc

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #5 on: May 26, 2014, 06:33:02 AM »
Top nurseries will also have vegetatively propagated rootstocks.

fruitlovers

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #6 on: May 26, 2014, 06:34:57 AM »
Commercially produced trees should just about always have the best rootstocks for the area. That would include the most disease resistant rootstock.

Should in this world unfortunately does not always result in does. If you don't have standing water in your planting hole and your tree succumbs to root rot then the nursery has not used a very resistant rootstock.
Oscar

fruitlovers

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #7 on: May 26, 2014, 06:36:32 AM »
Top nurseries will also have vegetatively propagated rootstocks.

That may be true in Australia perhaps, but is not true in USA. I believe most nurseries use seeds for their avocado rootstock.
Oscar

BMc

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #8 on: May 26, 2014, 08:42:14 AM »
We only have a few that do it, but they can supply big numbers to many nurseries. I can't quite remember how they do it, but it included, nurse grafting a root system to a cutting of an avocado that grew in a stagnant pond, growing on in a darkened shipping container (plantlets were white) then introducing to light and grafting the top. Pretty cool, and well worth the extra $10.

Ed of Somis

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #9 on: May 26, 2014, 09:49:30 AM »
Mike has given you some really good advice ...with common mistakes some people make. Is your soil volcanic??? This would be great. My soil is heavy clay...so my worries are well-founded.  It sounds like you are really more dialed-in than 90% of amateur growers. Do not whack out about it (I have in the past). Your Wurtz is not really a vigorous or aggressive growing tree. Those natural dwarfs (I have "Holiday") can be even tougher to grow than most. Sounds like you are doing fine...

fruitnewbie

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #10 on: May 26, 2014, 02:03:14 PM »
Thanks for your replies. Mike, thanks for your thoughtful insight. You are right, I am going nuts on the dolomite and will back off. Too much love can kill  :P.

My soil is oxisols which is old and weathered volcanic soil, acidic and frequently low in calcium. UH did a study showing that calcium will suppress root rot in this area. I know that I should do a soil analysis but have not gotten it together to send one in  :(. I will make a commitment to do it today.

Oscar, my plants for the most part are from Plant It Hawaii so I'm hoping they use seeds from some ancient tree growing in >100" of rain in Hilo. Your fruit are so lovely but I know it did not happen overnight. Patience is a virtue I think I have to work on...

I admit to being an OCD researcher when it comes to my trees.

This forum is so valuable to me. Thanks for all of your knowledge and willingness to share.

Aloha.

Jenna

fruitlovers

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #11 on: May 26, 2014, 06:23:45 PM »
Thanks for your replies. Mike, thanks for your thoughtful insight. You are right, I am going nuts on the dolomite and will back off. Too much love can kill  :P.

My soil is oxisols which is old and weathered volcanic soil, acidic and frequently low in calcium. UH did a study showing that calcium will suppress root rot in this area. I know that I should do a soil analysis but have not gotten it together to send one in  :(. I will make a commitment to do it today.

Oscar, my plants for the most part are from Plant It Hawaii so I'm hoping they use seeds from some ancient tree growing in >100" of rain in Hilo. Your fruit are so lovely but I know it did not happen overnight. Patience is a virtue I think I have to work on...

I admit to being an OCD researcher when it comes to my trees.

This forum is so valuable to me. Thanks for all of your knowledge and willingness to share.

Aloha.

Jenna

Yes Jenna Plant it Hawaii uses seeds for growing their rootstock. Using clonally propagated rootstock, as BMc describes, would be much better. But nobody here does that. Not all the seeds come from same tree, so some of their plants may have more resistance than others. But you should be just fine as long as your soil has good drainage. BTW, average rainfall where Plant It is located is more like 150 inches.
Oscar

Finca La Isla

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #12 on: May 26, 2014, 08:51:48 PM »
Another thing that can help is a program of applying EM, beneficial organisms.  They help with converting organic material into food for plants as well as directly attacking pathogenic fungi.
Peter

fruitlovers

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #13 on: May 26, 2014, 09:42:11 PM »
Another thing that can help is a program of applying EM, beneficial organisms.  They help with converting organic material into food for plants as well as directly attacking pathogenic fungi.
Peter

Yes agree. But also don't forget high organic matter content in soil. Should be 5% or higher organic matter. Organic matter in soil also helps promote beneficial fungi which will crowd out non beneficial fungi like phytophtora.
Oscar

fruitnewbie

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #14 on: May 27, 2014, 12:26:26 AM »
Peter, I use both Bokashi and EM. I kind of like the smell and so do the rats. I also incorporate some peat with the beneficial fungus that is impossible to remember how to spell. My first avocado will be $500 but the rest will be free.  ;D. Oscar, greater than 150 inches a year in Kurtistown? That's some rain! Thank God for volcanic soil.

The first Sharwil I planted I over-mulched with thick mulch and it croaked. Black roots, lost all it's leaves. It tried to bloom as a last attempt to survive. Then it turned into black twigs. Very sad.  :-[ I was over-eager and did not do my homework first. That was about a year a half ago and I think that I have learned a lot.

Hopefully someday I will post pictures of my "haul".

Aloha,
Jenna   

Tropicdude

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #15 on: May 27, 2014, 01:54:03 PM »
Trichoderma, is a beneficial fungi that kills the bad guys, it does not discriminate though, so if you suspect you have fungi problems Trichoderma is the predator you want.  but if you have healthy trees and just want to prevent the nasties, inoculating with beneficial fungi is a good thing.

http://www.avocadosource.com/journals/ca/ca_1978_v32_n4_pg_6_7.pdf

I should mention that beneficial fungi in an injectable foam, is being used to combat Laurel Wilt, in Avocado.

Also do not forget the Gypsum.


 
William
" The best time to plant a tree is 20 years ago.....The second best time, is now ! "

CTMIAMI

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #16 on: May 27, 2014, 08:09:47 PM »
William where did you get the information about an injectable foam lor Laurel Wilt?
Carlos
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OrganicJim

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #17 on: May 27, 2014, 09:02:16 PM »
Hendrikus Organics has both a liquid product to drench existing soil and a dry product that you add at planting that has natural biology in it that inhibits phytophthora. They are suppose to be in the Islands.

Mike T

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #18 on: May 28, 2014, 02:39:10 AM »
The breakdown products of vegetation mulch, animal decomposers and antagonistic fungi to phytophthora mean that thick mulch is the best strategy in the war on this fungal disease. A diverse assemblage usually turns up on its own.

 Excessive grass, fine sawdust or within 8 inches of the trunk can cause problems like water repulsion, lack of 02 to roots and a few other issues. Phosphonate is a tonic not a fungicide by the way and can be used topically, injected and even runoff on the ground helps.

Why use gypsum at all? As a clay breaker perhaps. It's effectiveness on clay is controversial but the nutrient imbalances caused by excessive application is a risk.More nutrient deficiencies in fruit growers gardens are caused by additives and fertlizers than are natural.

 

Tropicdude

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #19 on: May 28, 2014, 03:07:45 AM »
William where did you get the information about an injectable foam lor Laurel Wilt?

http://ars.usda.gov/is/pr/2013/130826.htm

Actually the fungi in the foam, kills the beetles that spread the wilt.
William
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CTMIAMI

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #20 on: May 28, 2014, 07:14:04 PM »
I sent Alex Rooney the lead researcher a note to see how is that test doing
Carlos
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CTMIAMI

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #21 on: May 28, 2014, 07:19:09 PM »
Plant Doctor according to their label is only 1/2 of a percent active ingredient. The professional products are over 50%  Plant Doctor is not a good value.
Carlos
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Josh-Los-Angeles

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Re: any tips on preventing phytophthora root rot in avocados
« Reply #22 on: May 29, 2014, 01:29:41 AM »
I've started using Potassium Silicate. It hulks out the plants, makes roots much stronger and makes leaves dense enough to prevent most pests from nibbling. There's a number of manufacturers, I paid around $15 for a liter that should last years. Here's an interesting article on SI preventing/alleviating avocado root rot:

http://www.avocadosource.com/journals/saaga/saaga_2007/saaga_2007_v30_pgs_49-56_bekker.pdf