Q.Weeping Willow, carpenter ant damage to upper exposed heart wood.
Upper third of tree broke off 1yr ago. Remaining trunk left exposed. This exposed heart wood of main trunk became infested with carpenter ants (now eradicated). Damaged heart wood removed leaving cavity 2m depth by 0.3m cylinder. Healthy bow remains stemming from upper damaged area. Outer bark basically intact and secure.
How do we fill this to prevent rain, animals, insects etc. from re-entering and causing further damage?
Tree sited in SW France, enclosed garden, surrounded by other trees and shrubs. Age 40-50yr approx.
In most cases tree wounds and damage should be left uncovered to let the tree heal itself.
Just from the description, your tree sounds very compromised. I would suggest a certified Arborist inspect the tree for the best coarse of action.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/trees/tgen/wound-dressing-on-trees.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/home-remedies-carpenter-ants.htm
