Tree decline is a progressive deterioration in the health of a tree that is attributed to a combination of factors, such as competition among plants, environmental stresses, injuries and diseases like defoliating leaf diseases, root rots, wilt diseases, and nematode infestations in the soil. Although each of these may be unimportant individually, in combination they may cause decline and death of the plant. Avoid unnecessary injury. To avoid stress, know and supply the maintenance needs of the plant. Water deeply during dry periods. Don’t induce rapid top growth by applying high nitrogen fertilizers to the root zone.