Hi Kage,

The soil disturbance around the base of your Quercus is very probably caused by the ants themselves. They can move quite a lot of earth around when making their underground nest chambers.

The ants won't harm the tree directly, but they may well be "farming" aphids on the foliage - they harvest aphid honeydew and in return keep predators away from the aphids - so check carefully for the presence of aphids since a large infestation can cause considerable damage to a young tree. If there are aphids present then they need dealing with as a priority.

Although ants are a very important part of any garden ecosystem they can be problematic if they turn up in the wrong place. Depending on the size and species of ant and the consequent size of their colony, they may also be causing substantial disturbance to the roots of your young tree, particularly if they are excavating at the very base of the plant. This can leave large air pockets and lead to the death of some of the roots, which in turn allows fungal disease to enter the plant.

If the colony is small then I would leave them alone, but if there is lots of excavation then I'd use a nematode to disperse them away from your tree:

http://www.ecocharlie.co.uk/grow-your-own/pest-and-disease-control/nemasys-no-ants.html

Hi, thanks very much for your reply, the ants are only a few, but they are there every time I go to the tree. Its not them who is disturbing the soil though, I think it is probably hunting dogs as the tree is near a hunting area. I put some plastic sheets around the base of the tree just under the soil to keep the soil moist and to keep the water from evaporating, every time I go to the tree lately the plastic sheets have been dug up and are nearby the tree.
Last time I went to water the tree I put the soil back in place and the plastic over it, and then I covered it with some rocks to keep it in place, but it was dug up again! So this time I put the soil in place again and the plastic over it, and then I found the biggest heaviest rocks I could find to put over the top. Fingers crossed! Do you think its possible that the hunting dogs can smell my scent at the tree and try to dig up whatever is at the base of the tree? Its starting to get annoying, and now that its quite hot here in France the tree is looking really dry (thats why I put the plastic in place, to keep it moist)

thanks very much for your reply

Hi Kage,

Was the tree planted with manure or bonemeal, blood, fish and bone, pelleted food granules or anything like that? All of those are highly pungent and will attract badgers, foxes and dogs too, otherwise I'm not sure why they would be so interested in disturbing the plastic sheeting and digging directly into the plants roots.

In any case I think your solution of using the biggest rocks you can find will probably be the best one! Of course those same rocks will also help to keep the ground a little cooler and help to reduce water loss too.