Poplar trees grow very fast and grow throughout North America. They are often used for paper and particleboard production and biobased products, such as fuels and adhesives. Poplar trees are susceptible to some diseases that must be taken care of as soon as possible to prevent damage to the tree.
Leaf spot can appear on poplar trees as white, silver, brown or tan marks or circles on the leaves. Leaf spot can cause leaves to dry up and drop off prematurely. It is usually caused by a fungus, so remove infected twigs and leaves to prevent it from spreading. Though leaf spot will not kill the tree on its own, it can make the poplar more susceptible to other diseases and pest infestations.
Established poplars infected with fungal infections that cause shoot blight are not usually severely damaged, but the disease can cause new shoots and growth to die. Shoot blight causes young shoots and leaves to turn black and shrivel up. The fungus spreads best in moist conditions. Poplars affected by shoot blight should be sprayed with a fungicide every 10 days, according to North Dakota State University. Shriveled shoots and leaves should be removed and burnt to prevent the spread of the fungus.
Several different kinds of parasitic fungi can cause cankers on poplars, killing portions of the bark. Entire branches can be lost if several cankers cluster and grow together. A poplar can die if cankers spread to more than half the diameter of the trunk. Bark infected with cankers rots and opens the tree up to infection by other parasitic pests. The canker can also cause the tree to ooze bad-smelling sap. Poplars should be provided with adequate water and fertiliser, as drought increases the risk of cankers. Branches infected by cankers should be cut and buried or burnt to prevent the disease from spreading.
Poplar rust usually appears after midsummer. The disease is caused by a fungus that manifests as yellow blisters on the lower portion of the leaves. As winter approaches, the leaves become encased in orange or brown waxy crusts. Rust spores from an infection can spread quickly to other poplars and other trees. Fungicide sprays can help protect poplars from rust fungi.