There are many things to consider when planting trees next to buildings and along roads or avenues. This is a non-exhaustive list of tree species that I recommend for our region (Auroville, India) in the typical laterite or black cotton soil. This is an evolving list.
General species selection criteria:
Not prone to structural failure
No dangerous fruit (falling risk-wise and also poisonous plants taken into account)
Ideally with interesting features (bark, leaves, flowers, shape, fruit etc…)
No buttress or superficial roots (surface roots that would disturb pavement, hinder traffic)
Little mess in terms of fruits, flowers, foliage (apart from fruit trees)
Important for local ecology
Large evergreen trees to be used as shade for houses or avenues
Yes, neem trees lose their leaves every year, sometimes multiple times but, if a tree ends up with dead leaves up in the canopy then there is a problem due to an external factor. Yes, neem dieback has been around for some time and some trees recover from it. All neem trees that I have inspected have been affected by this to some extent. Older trees, very young trees and trees in poor condition or environments will likely be the most affected.
In the image below is the tea mosquito (Helopeltis antonii)which is one way that the fungus (Phomopsis azadirachtae) is transimitted which then causes the specific neem dieback disease (scientific evidence below).
Generally, all trees can be vulnerable to drought, especially to prolonged drought. It depends on their condition and the extent of the drought. With regards to excessive rain, if the roots are submerged for an extended period, they will not get oxygen, so they won’t be able to sustain their system (they can’t burn sugars). This FAO document mentions drought and neems. It is how I eventually came to the conclusion that the neems will not be able to deal with this very well (but it is likely to be consisting of even more factors).
The succession of detrimental events is the usual course for the death of a tree. Unlike us, they are not programmed to die. So, if a tree is affected by a disease, it is then more susceptible to other diseases.
From what I understand (or think I understand) the C4 compost acts a positive environment for germination for the bacillus which then will merge with/inoculate the absorbing roots (which will also be prompted to grow due to the new richer environment, hence the combination). Then the Bacillus will induce systemic acquired resistance (which should help with the Phomopsis) along with potentially helping with uptake of water and nutrients through synergies with mycorrhizal fungi.
To give an idea of what could be affected, when surveying about half of Auroville excluding the “Greenbelt” (~2.5 square kilometres) Geomatics have recorded over 3000 neem trees. So there are potentially over 20,000 neem trees in Auroville.
Here is what has been achieved in Auroville, regarding treatment, so far (I am only involved in some of this):
Contributing financially (it costs about RS55 per tree just for the materials and we are all doing this for free) by using the temporary Auroville FS account for this: 253042
Letting me know if you have other methods which work
Inspecting the trees, plotting them and then monitoring them to see how the treatment is acting
I am happy to come by (locally) and explain, show, teach (can be part of a school or research project).
Please let me know if you treat trees somewhere so we can record it (to later check if it works as intended and get statistics. If you want to be involved in this aspect, that is also possible).
This is the first step in setting up a response to a potentially huge loss of neem trees. All networking and collaboration could be improved and should be and if you want to coordinate efforts, please do so as I do not need, or necessarily want, to be involved.
If you have any other ideas, please suggest them (especially if you want to do the legwork).
A brief article to inform people of how to go about digging near trees and why it matters.
Digging occurs for many reasons but the most important (for the tree) usually occurs when a trench is being dug for foundations or utility, such as for cables or pipes (there are many ways tree roots can be damaged but I am concentrating on digging damage).
Tree roots, usually, do not go below a meter in depth in the ground as there is not enough oxygen below to sustain them (through respiration). This is why it is usually feasible to dig under tree roots (Figure 8.16) instead of through them to install cables and pipes. For trees with tap roots, one can dig under the roots but to the side of the stem rather than directly under it.
Construction work near trees should be properly evaluated as most root damage to trees often occurs during this time but the effects will only be seen several years later.
Here is an example of poor planning and devastating results:
A new construction was planned to go around this tree (image) as it was a central focal point. The tree was not considered sufficiently. The result was that many roots were destroyed during excavation and a main branch was to be removed. I was called in by the owners who could clearly see that the tree had become a hazard as the above ground parts stretched for over 15 meters each direction and the below ground parts were all cut off at 1.5 meters in each direction. The only outcome was removal of the tree as the stability and health of the tree was severely compromised.
Construction work near trees should be properly evaluated as most root damage to trees often occurs during this time but the effects will only be seen several years later. The UK minimum root protection area is 12 times the diameter of a tree measured at 1.5 meters from ground level (a 12 meter radius for a 1 meter diameter tree). Before digging within this area root presence or absence should be verified. Foundations within this area are most often of the pile variety rather than the typical trench foundation.
Please think next time you want to dig near trees, especially if you want to build as close as you can to that special tree, because that may just shorten its life time significantly and defeat your purpose.
If you want more info, clarifications or advice, you are welcome to contact me. firstname.lastname@example.org or 7598103616