Tree Pests and Diseases

Asian Long-Horned Beetle

The Asian Long Horned Beetle (ALB) causes widespread mortality of poplar, willow, elm and maple trees. The beetle is a large black insect with white spots dashed irregularly on its wings. The distinctive long antennae that give the beetle its name are as long as the body in females and almost twice the body length in males.

The ALB is considered an invasive species in North America, where it is a serious threat to many deciduous hardwood trees. During the larval stage, the ALB bores deep into a tree's heartwood, where it feeds on the tree's nutrients. The tunneling damage within the cambium layer of the bark and eventually kills the tree.

Aphids

Aphids, also known as plant lice, have piercing/sucking mouth parts. Aphids infest new foliage on both annual and permanent plants, usually in spring or early summer. Aphids ingest the fluids from a tender leaf or stem tissue of the plant, depriving it of nutrients. They can also spread disease by moving from one plant to another. For severe infestations, an Urban Forestry representative will spray a strong jet of water or soap/water mix directly onto the affected area of the plant to wash the insects off.

Carpenter Ants

The red carpenter ant and the black carpenter ant are two of the most common types found in Canada. The red carpenter ant has a dark brownish-black body, with a reddish-brown upper body. The black carpenter ant is dark brownish-black all over.

A carpenter ant's body is divided into three segments, with a very slim waist separating the upper body and lower body. Their antennae are bent and in sections. Male and female adults have wings at mating time. The mere presence of carpenter ants within a tree suggests premature rotting within the tree's core.

Emerald Ash Borer

The Emerald Ash Borer (EAB) is a highly destructive insect that attacks and kills ash trees. Native to eastern Asia, EAB was first discovered in Windsor, Ontario, and Detroit, Michigan, in 2002. In 2008, the Canadian Food Inspection Agency (CFIA) confirmed the presence of EAB in Brampton and other neighbouring municipalities. Invading Species – Emerald Ash Borer.

Locust Plant Bugs

Locust Plant Bugs feed on the developing buds and leaves of a plant. They use a “lacerate and flush” feeding style that causes a lot of damage to the feeding site, which often destroys young leaves and buds. Older leaves may survive, but show discoloration and deformation of developing foliage due to localized necrosis around feeding points.

Spongy Moth

The Spongy Moth is a defoliating (feeding on leaves) insect that is considered a major pest in North America. The caterpillar, or larva stage of the insect, eats the leaves of trees making them more susceptible to disease and damage from other insects.

Wasps and Hornets

A wasp is a predatory, flying, stinging insect. A Pest Management Specialist will respond to all public concerns regarding wasp and hornet nests in City t​rees. A nest will only be destroyed if it is located on branches no higher than 5 metres (16 feet) above the ground.

Apple Scab and Rust

Apple Scab is one of the most common diseases of apple and flowering crabapple. The disease causes premature defoliation and a reduction in the number and quality of flowers the year following defoliation. Apple Scab first appears in early spring, especially on years with high levels of precipitation, as roughly circular, velvety, olive-green spots on both the upper and lower surfaces of leaves. The spots eventually turn dark-green to brown and develop a rough texture. Usually the fruiting bodies can be found on its alternative host, Junipers (Juniperus virginniana) commonly found throughout eastern Ontario.

Dutch Elm Disease

Dutch Elm Disease (DED) is often confused with other tree diseases such as Elm Yellows, Leaf Miner and Leaf Scorch. DED causes leaves to wilt and turn yellow, eventually changing to brown. Symptoms can be seen in the early summer, but may show any time in the growing season. Elms are used widely in urban forestry and along city streets. DED can affect entire rows of trees by transmission through the underground roots. Elm beetles are also attributed to the spreading of the disease.

Leaf Scorch

Leaf scorch may occur on any species of tree or shrub. Leaf scorch most often occurs following prolonged periods of dry or windy weather when the roots are unable to supply water to the foliage. It causes the browning of plant tissues and the darkening or yellowing of plant veins. In mild cases of leaf scorch, the leaves remain attached and little damage results. In more severe cases, plants may drop many of their leaves prematurely.

Powdery Mildew

Powdery Mildew is a fungal disease that affects a wide range of plants. It is one of the easiest diseases to spot, as its symptoms are quite distinctive. Infected plants display white powder-like spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any part of the plant. As the disease progresses, the spots get larger and thicker as massive numbers of spores form.

Tar Spot

Tar spot cause round black, tar-like spots on infected leaves of Maples, which are not noticeable until late summer. Tar spots of maple are caused by fungus. The thickened black spots are fungal tissue called stroma. Red, silver, Norway and Manitoba Maples as well as others are affected by tar spot diseases.