The hybrid poplar is a fast-growing shade tree used extensively in landscapes throughout the US since the 1970s and is susceptible to a variety of diseases. In addition, the short-lived hybrid poplar has shallow roots that produce suckers or small trees around its base, which can interfere with mowing equipment.
Septoria canker is caused by the Mycosphaerella populorum fungus. The infection begins by appearing under the bark of the main trunk of a limb. Eventually, the bark falls away and exposes the sunken lesion. The fungus expands and girdles the tree or limb, causing the death of the portion of the plant that is above the infection. It is wind-borne and difficult to diagnose because of numerous secondary infections that can follow damage from the initial Mycosphaerella populorum fungus infection.
Septoria Leaf Spot
Septoria leaf spot is caused by the septoria bacteria that infects the leaves from splashing rainwater and wind. It appears in mid- to late-summer. Septoria leaf spot appears as irregular brown spots with a black center, then spreads throughout the leaf. The infected leaves die and fall off the tree where wind and splashing water carries the bacteria back to the tree the next growing season.
Slime flux is caused by a bacteria that enters the tree when it is pruned or damaged in some way. The bacteria settles in the middle of the tree and feeds on the heartwood.
Eventually, the heartwood begins to decay and gasses are given off by the bacteria during the natural decaying process. The gases create pressure inside the tree and sap begins oozing from weak spots on the tree. The oozing sap creates an unsightly appearance and attracts damaging insects to the tree.
Verticillium wilt shows up as dead and dying portions of the tree after or during a drought. It is a soil born fungus that travels through the root system or may be wind-borne where it enters the tree through wounded tissue. It can cause sudden death of the tree in severe cases.
Shoot blight is caused when the Venturia populina fungus infects new growth. New green shoots suddenly turn black and die. It appears where foliage is shaded or remains unnaturally wet for long periods of time such as near a water sprinkler..