Kauri Dieback Disease. Please Check Your Kauri Trees Commonly known as PTA (phytophthra taxon Agathis): Symptoms. Yellowing of foliage, Canopy thinning, Dead branches, Trees can develop lesions that bleed resin, extending to major roots and sometimes girdling the trunk as “collar rot”. The disease can kill trees and seedlings of all ages. If you observe a kauri tree on your land with any of the above symptoms please advise the appropriate authorities immediately.