Hardwood leaf diseases in Arizona and New Mexico are most often observed
on aspen, Arizona sycamore, cottonwood and willow. Although clonal
susceptibility to foliage pathogens is common for aspen and willow,
whole areas can become infected during favorable moisture periods.
Severe infection can cause premature defoliation and reduced tree
growth.
Figure 174. Foliar diseases can cause premature defoliation.