Problems With Hybrid Poplars

Hybrid poplars were bred and selected for vigorous growth, tolerance of environmental stresses and resistance to pests and diseases. Even so, they still have several problems that affect their appearance and health. Hybrid poplars are used in landscapes as fast-growing shade trees and windbreaks. They are grown commercially for pulp for paper products, wood stove pellets and some types of lumber.

Although hybrid poplars grow quickly, they are short-lived trees with brittle wood that breaks easily. The shallow roots are invasive and can send up new shoots as far as 80 feet away from the main tree. Some hybrids drop gummy buds in the spring that stick to shoes and are carried into houses and cars. Female hybrid poplars drop cotton-like pieces of fuzz that can clog water pumps on pools and ponds. In addition, the fuzz is flammable. Deer and other wildlife are attracted to hybrid poplars and will chew on the foliage and bark.

Numerous pests feed on the foliage of hybrid poplars and can cause defoliation of the infested trees. The brown larvae of satin moths feed on the foliage and can cause severe damage. Willow leaf beetles, small metallic blue or blue-green beetles, can also defoliate trees. The larvae of poplar willow sawflies and poplar leaf beetles feed on the foliage and can defoliate trees. Some hybrids are very susceptible to these pests, but some hybrids are fairly resistant. Disease pathogens enter hybrid poplars through holes drilled by poplar borers. These holes also degrade the wood and weaken stems and branches, which then break. A severe infection of aphids, a type of sucking insect, can reduce the growth of young hybrid poplars. Eriophyid or rust mites cause the leaves to cup and turn bronze. Tarnished plant bugs are small brown flying insects that inject toxins into the trees. The toxins stunt the growth of young hybrid poplars, distort the leaves and cause canker-like lesions on young stems.

Leaf rust causes orange or yellow pustules on infected foliage. Defoliation occurs as the disease progresses, and the tree weakens and becomes susceptible to other diseases. Marssonnia leaf spots also cause lesions on the foliage and petioles. Hybrid poplars are very susceptible to Septoria leaf spots, which can cause defoliation. Some hybrids are resistant to Venturia leaf spots and some are susceptible. The disease causes blighted tissue on foliage, shepherd’s crooks on new shoots and small cankers on twigs.