&middotDrought damage - needles gradually turn yellowish-green and then light brown. This starts at the top of the tree and progresses downward and from the outside in. &middotAnimal injury - dog urine can cause some browning and dropping of lower branches on arborvitae and junipers.
There are many different brands of cat flea collars. Generally, flea collars work by either emitting a toxic gas to the local area (head/neck of the pet) or by exuding chemicals that are absorbed into the animal's skin. Some flea collars have an Insect Growth Regulator (IGR), to prevent development of cat fleas, eggs and larvae.
No! The only use of cat flea collars that I recommend is to use them to kill fleas inside your vacuum canister. Cut the collars into pieces and place the pieces in the vacuum bag. That way, when the fleas are vacuumed in, they are killed. They cannot escape from the vacuum and go back into your home.