Mango leaf problem.

[alanrchase]

Firstly I am not a farmer but have a large garden with a lot of mango trees. The mango trees are all grafted varieties planted by us and range from a few months old to about 20 years old. Every year I get a problem with the new growth getting covered in dark spots and becoming shrivelled.  There is also a problem with what I believe to be leaf cutting weevils. I have had some success against the leaf cutting insects by spraying cypermethrin. Can anyone give any advice on what is causing the dark spots and shrivelled leaves and how to prevent it please?

 

[fredwiggy]

Try this........................https://www.frontiersin.org/articles/10.3389/fmicb.2023.1168203/full

[alanrchase]

1 hour ago, fredwiggy said:

Try this........................https://www.frontiersin.org/articles/10.3389/fmicb.2023.1168203/full

Thanks for the link. I tried spraying with Bordeaux mixture last year which is a copper fungicide with mixed results. The black spots and shrivelling only seem to affect new growth and don't seem to spread to twigs or older growth. I have some copper and lime left over from last year so may go round spraying tomorrow and see if it helps.

[drtreelove]

That's a very thorough paper on Mango Athracnose Disease.  Read the entire article and recognize that its never a good idea to reach first for chemical treatments, cypermethrin or bordeaux mixture or any other quick fix dreams. 

 

In my professional opinion, based on over 50 years as a tree care professional, as my father before me, that its always best, for any pest or disease problem to look first at the growing conditions, soil and water management to determine why that pest or disease is there in the first place and what you are doing or not doing to create the conditions that make those trees susceptible to biotic and/or abiotic disorders. Because healthy plants grown in heathy soil don't get pests or diseases, and that is a well established scientific and practical truth of IPM (Integrated Pest Management) and the Soil-Food-Web, Regenerative Ag movement.  

 

"The mango trees are all grafted varieties planted by us..."  Recognize that grafted varieties are usually bred for desireable fruit characteristics and often not so much for resistance to disease. This is a critical factor in IPM. 

 

Chemical fungicides should not be depended on as a stand-alone, or a long term treatment. IPM considers a much wider viewpoint, especially the environmental and cultural factors that contribute to resistance or susceptibility. If you don't improve the growing conditions and management of watering, soil and plant health, then you are fighting a losing battle.  Also, if you are using high salt index, high NPK chemcial fertilizers, are not mulching and/or cover cropping, then the problems will be exacerbated. And if it's not one thing (MAD), it will be another ("There is also a problem with what I believe to be leaf cutting weevils.") 

 

From the article: "Alternatives to fungicides have been developed in light of rising awareness of the fungicides’ deleterious effects on human health, the presence of fungicide residues in mango fruits, and the contamination of the natural environment that results from their widespread use. Essential oils, botanicals, and oxalic acid treatments have all been shown to be effective alternatives to chemical control, especially in locations where the use of synthetic fungicides is prohibited. Microbial agents and biological control of the MAD have also broadened developmental prospects for establishing environmentally friendly pest management."

 

If you are still reaching for chemical treatment as the first response to plant problems, then you are way behind the times with modern plant science and environmental, biological awareness and practical treatment modalities. 

Biologicals 101.pdf

[ozimoron]

Some species of mango are more susceptible than others. I owned a commercial mango farm in oz for 15 years. I used to spray mancozeb soon after the fruit set and then copper every 2 weeks.

 

https://industry.nt.gov.au/__data/assets/pdf_file/0005/233591/604.pdf

[drtreelove]

First recommendations:

 

1. Review and improve your watering program for during the dry season. Not too much or too little. Drought-stressed trees will be more susceptible to pests and diseases, decline and die-back. 

https://www.fertileearthlandcare.com/watering-trees/

 

2. Soil fertility. Avoid high NPK chemical fertilizers. Use biologicals, real compost, vermicompost/worm-castings, aged/composted manures, COF (complete organic fertilizer), hydrolized fish fertilizer, and mulch the soil surface throughout the tree root zone (dripline and more).  This may be practical for small home orchards, but larger commercial orchards must consider costs of inputs and more economical alternatives like well managed mixed-species cover cropping. 

 

Some examples of local Thailand sources for biologicals: 

 

COF and Vermicompost

https://www.facebook.com/bestgardenstate/

 

https://maruchubussan.co.th/product/takumi-organic-fertilizer/

https://maruchubussan.co.th/product/fish-amino-organic-fertilizer/

 

3. Biocontrols  With good watering and soil restoration practices in place, then biological fungicides and botanicals can be used with greater effectiveness. (They are not a stand-alone substitute for chemical fungicides, they don't work in the same way. They must thought of as components in a comprehensive IPM program.)

 

 

Bokashi fertilizer.docx

[drtreelove]

1 hour ago, ozimoron said:

Some species of mango are more susceptible than others. I owned a commercial mango farm in oz for 15 years. I used to spray mancozeb soon after the fruit set and then copper every 2 weeks.

 

https://industry.nt.gov.au/__data/assets/pdf_file/0005/233591/604.pdf

 

This is of course a viable conventional approach for commercial growers who are not yet on board with modern ecological farming methods and materials and efforts to adopt practices that are more earth and climate friendly. A losing battle maybe, but some of us think its important to try. 

 

From your countryman Dr Christine Jones, Australian soil microbiologist (https://amazingcarbon.com/)

 

cover cropping orchards and vineyards

https://youtu.be/PJs8GU1cG30?si=aKmMgXp1oCSDH112

 

why change

https://youtu.be/SYRpFqUlK78?si=iUJnvKVDJtGt5boK

 

 

[ozimoron]

10 minutes ago, drtreelove said:

 

This is of course a viable conventional approach for commercial growers who are not yet on board with modern ecological farming methods and materials and efforts to adopt practices that are more earth and climate friendly. A losing battle maybe, but some of us think its important to try. 

 

From your countryman Dr Christine Jones, Australian soil microbiologist (https://amazingcarbon.com/)

 

cover cropping orchards and vineyards

https://youtu.be/PJs8GU1cG30?si=aKmMgXp1oCSDH112

 

why change

https://youtu.be/SYRpFqUlK78?si=iUJnvKVDJtGt5boK

 

 

 

I'm totally on board with using natural methods for anthracnose control. I do think it's probably for smaller orchards up to about 10 acres but more than that might, as you suggest, be a losing battle, especially in humid areas. Like all tree diseases, close mono cropping makes pest and disease control difficult 

[drtreelove]

4 minutes ago, ozimoron said:

 

I'm totally on board with using natural methods for anthracnose control. I do think it's probably for smaller orchards up to about 10 acres but more than that might, as you suggest, be a losing battle, especially in humid areas. Like all tree diseases, close mono cropping makes pest and disease control difficult 

Well said! Yes, mono-cropping has its advantages of course, and in fact is considered a necessity for large commercial orchards. But it comes with potential horendous problems.