Damage caused to poplar seems to be primarily a reduction in photosynthetic area because of necrosis and early defoliation. Impact on poplar growth can be severe. The disease is best controlled by avoiding susceptible clones. Melampsora needs alternate host plants. The disease infects hosts in several ways.
Heavy infection causes premature senescence of leaves and defoliation.
Uredial pustules of some rusts act as sinks to accumulate metabolic products in competition with other plant parts. Leaf rust is best controlled by planting resistant poplar clones. Some fungicides could be applied. The heartwood of cottonwood is brownish colored and sapwood whitish. The definition between them is not clear.