Mango tree borer - Rhytidodera bowringii

[wolfmuc]

In our mango orchard in Thailand North we have beetles that might kill the trees.

It's not the 'Batocera rufomaculata' or someone else, no, his/her name is

Rhytidodera bowringii. Pictures below.

 

These days (in May) they seem to emerge. I'm afraid that their life circle will continue:

female laying eggs / larvae eating, growing / next generation emerging and so on.

' In heavy or continuous infestations, tunnelling weakens the wood to such an extent

that branches break or the main stem collapses. ' - Yes, indeed.

 

I am spraying a mixture containing azadirachta/neem but am very doubtful about this.

Because it is a very strong beetle.

 

Thanks for any ideas.

 

 

Rhy. bowr. - 1 Foto.docx

[soidog2]

Unfortunately spraying will not help trees already infested. You must visually inspect each and every tree, look for telltale signs, such as active holes and excrement on the trunks.

Where you find them, use a small chisel or other tool to dig out and kill the larvae, Use a strong insecticide such as chaindrite and spray inside any hole or trail you can find on the trees trunks or branches. The trees will recover if the infestation is manageable.

Any tree that is too far gone must be cut and burned ASAP to stop spreading the bugs. In the future maintain your trees with a systemic agent to prevent infestation.

Good Luck, 

[wolfmuc]

soidog2 - Thank you very much for the proposals.
Sounds good, even if it will be a lot of work  - 'each and every tree' -
But cut, chop and burn should be the very last option.

In Hainan, China there was a similar problem in orchards about 30 years ago. I found two articles,
unfortunately in Chinese language but with an English abstract.  
Quote: ‘The borers can be controlled by cutting off the infected branches and  plugging the tree holes
below the affected area on the stem with cotton soaked in 20% Fenva-lerate.’
‘Holes chewed by R. bowringii larvae were blocked with cotton balls dipped in different concentrations of
deltamethrin (2.5 % (V/V), and then wrapped tightly with polyethylene films. - can kill all of the larvae and eggs.’
You suggested Chaindrite. It contains Cypermethrin and Imiprothrin. So, that’s a good sign…
Thanks again.

[soidog2]

I didn't promise it will be easy but its the only way to save your trees.

Trees with infestation older than this year; generally speaking are not worth saving because their trunks are crisscrossed with larvae channels; weakening the trees even if outside they look healthy.

On those trees yields will be very poor and in a windstorm they will snap and cause damage all around.

Cut, burn, kill the bugs, plant new; with the right trees; 3-4 years will start producing.

If the infestation is above knee height or higher level; remove the entire canopy burn it, protect the stump from sunburn and new infestations, in a couple of years the trees will rejuvenate.

 

[wolfmuc]

Thank you for your clear words, really appreciated.

It's a pity cutting these trees, but I think you're absolutely correct.

By the way, found other mango borer larvae these days. About

half as long as the Rhytidodera larvae.

(new grub picture down right.)

Thanks again.

[drtreelove]

On 5/11/2017 at 0:24 AM, soidog2 said:

In the future maintain your trees with a systemic agent to prevent infestation.

Good Luck, 

Systemic insecticide on a food plant is not advisable, it can end up in the fruit. And even for ornamentals, systemics that are effective for beetles/borers are very limited.  Especially larvae that are feeding in the heartwood and weakening the structure, as opposed to those that feed in the growing layer and sapwood where the  insecticide would be concentrated.

 

The only systemic that is organic program compatible is a water soluble azadirachtin that is not available in Thailand as far as I know. Azasol from ArborJet  is available in the US and Soluneem  in India. It has to be applied to the soil for root uptake, or formulated for stem injection.  Oil based neem products will not translocate systemically. 

 

A 'bark banding' barrier treatment is the best preventive and only practical and affordable method.  But the external azadirachtin barrier only has a residual effectiveness of about one or two weeks. A synthetic pyrethroid, like permethrin, cypermethrin, deltamethrin, bifenthrin mixed at a high label rate and sprayed on the trunk and all woody stems and branch structure can be effective. But only as preventive, not cure. 

 

Keep your trees adequately irrigated. The borers will be more likely to attack drought stressed trees. 

 

[wolfmuc]

drtreelove - thank you for the valuable suggestions.

I'm in a hurry leaving Thailand, so the work has to wait.

May be I might find something like Azasol or Soluneem

in Munich. - In the meantime rainy season will help irrigating the trees...

Again, thank you very much.