Hello Everyone. I am training my pine tree for bonsai. Some of the old needles on the pine began to appear yellow in color. Some of them started to turn brown from the base. The new growth on the pine is growing pretty well. This problem is present only in lower branches of the pine. I was checking on the internet and came across dothistroma needle blight. I was wondering if some one can identify whether it is dositherma or any other problem and what will the possibly solution. I am little confused and worried right now. Some of the pictures are attached herewith.