Landscape hemlocks in the Baltimore – Washington area were infested by the woolly adelgid in the late 1980’s and natural stands in the area became infested by 1990. The infestation steadily moved westward through native stands of hemlock in Frederick and Washington Counties in the mid-1990’s, Allegany County in 1999 and Garrett County in 2001.

Hemlock woolly adelgid is most easily recognized by the white “woolly” wax they produce on young hemlock twigs. The “wool” is present all year, but is most abundant and conspicuous during the spring and fall when egg masses are present. Most other stages in the life cycle are much harder to see. Fully grown woolly adelgids adults are only about the size of a period on a printed page.

Over 100 species of hardwoods are recorded as hosts. Preferred species of the fall webworm include black walnut, ash, hickories and oaks.

Moths emerge in the spring and lay eggs. The newly hatched larvae construct webs which they enlarge as needed. Larvae feed gregariously within the web for 4 to 8 weeks. After feeding, the larvae migrate and pupate in the soil. There are two generations of fall webworms per year.

Although not considered a serious forest pest, their unsightly webs can affect aesthetic value of landscape and roadside trees. Biotic factors usually keep populations in check so that chemical control is only rarely necessary.

Because of its ability to spread internally or systemically within the plant and to kill the plant, verticillium wilt is considered a serious disease. However, compared with a wilt disease such as Dutch elm disease, verticillium is less severe. Verticillium wilt is often confused with other diseases or biotic conditions. Herbicide damage, adverse environmental conditions and mechanical damage may cause the same or similar symptoms.

Symptoms caused by verticillium develop anytime during the growing season, but are most apt to appear in July and August. In some cases the symptoms may be more severe during or following cool weather. Symptoms appear chronically, or they may be acute and often lethal. Chronic symptoms include small, yellow foliage, leaf scorch (marginal browning), slow growth, abnormally heavy seed crops and dieback of shoots and branches. Often, the foliage on one or more branches wilts suddenly. Acute symptoms include leaf curling, drying, and an abnormal red or yellow color of leaves or areas between leaf veins, partial defoliation, wilting and branch dieback. Often one branch or one side or sector of the plant is affected.

Recurrence of wilt in ensuing years is unpredictable, as is its severity. In its lethal form, verticillium wilt will cause a sudden and total collapse of the plant.

Populations fluctuate from year to year, with outbreaks occurring every several years. Defoliation of trees, building of unsightly silken nests in trees, and wandering tent caterpillars crawling over plants, walkways, and roads cause this insect to be a pest in the late spring and early summer. Eastern tent caterpillar nests are commonly found on wild cherry, apple, and crabapple, but may be found on hawthorn, maple, cherry, peach, pear and plum as well.

While tent caterpillars can nearly defoliate a tree when numerous, the tree will usually recover and put out a new crop of leaves. In the landscape, however, nests can become an eyesore, particularly when exposed by excessive defoliation. The silken nests are built in the crotches of limbs and can become quite large.

Larvae cause considerable concern when they begin to wander to protected places to pupate. They are frequently seen crawling on other types of plants, walkways, and storage buildings. They are a nuisance and can create a mess when they are squashed on driveways, sidewalks, and patios. But keep in mind that no additional feeding or damage is done by the wandering caterpillars.

Eastern tent caterpillar nests are frequently confused with fall webworm nests. Unlike the tent caterpillar, fall webworm nests are located at the ends of the branches and their loosely woven webs enclose foliage while the tents of the eastern tent caterpillar do not. While there may be some overlap, fall webworm generally occurs later in the season.

Following severe infestations of spider mites, leaves become discolored, producing an unthrifty gray or bronze look to the plant. Leaves and needles may ultimately become scorched and drop prematurely. Spider mites frequently kill plants or cause serious stress to them.

Spider mites (Family: Tetranychidae) are classed as a type of arachnid, relatives of insects that also includes spiders, ticks, daddy-longlegs and scorpions. Spider mites are small and often difficult to see with the unaided eye. Their colors range from red and brown to yellow and green, depending on the species of spider mite and seasonal changes in their appearance.

Many spider mites produce webbing, particularly when they occur in high populations. This webbing gives the mites and their eggs some protection from natural enemies and environmental fluctuations.
Webbing produced by spiders, as well as fluff produced by cottonwoods, often is confused with the webbing of spider mites.

Rust fungi are very easy to identify on the plant. It can be characterized by a rust color on plant leaves and stems. The rust will start out as flecks and will eventually grow into bumps. The plant rust will most likely appear on the underside of the leaves of the plant.

The good news is that there are so many kinds of rust fungi and they are so plant specific, that if you see the rust color on plant leaves of one type of plant, you will not see it appear any other types of plants in your yard.

The excess water makes it very difficult for the roots to get air that they need, making them rot. To avoid root rot, it is best to only water plants when the soil becomes dry, and to put the plant in a well-drained pot. Using a heavy soil, such as one dug up from outdoors can also cause root rot.

A large number of root rots are caused by members of the water mould genus Phytophthora. Perhaps the most aggressive is Phytophthora cinnamomi. Spores from root rot do contaminate other plants, but the rot cannot take hold unless there is adequate moisture. Spores are not only airborne, but are also carried by insects and other arthropods in the soil.

A plant with root rot will not normally survive, but it can often be propagated so it won’t be lost completely. Plants with root rot should be removed and destroyed.

Egg laying begins shortly after the peach tree borer emerges and lasts only a few days. The eggs are deposited on the trunk at or near the base. Females lay 500-600 eggs on average. The larvae will begin to hatch in 9 to 10 days. Upon hatching, the larvae wander down the trunk to the soil line and burrow into the bark, often entering through a crack or wound. When full grown, the larva is 1-1/4 in long, cream colored with a dark brown head. The winter is spent as a larva under the bark. In the spring the larva will construct a silken cocoon and cover it with tiny bits of chewed wood. The peach tree borer will remain in the pupa stage from 18 to 30 days before emerging as an adult. There is a single generation per year. Infestation by the peach tree borer is often identified by oozing of gum around the base of the tree. The gum is usually mixed with dirt and reddish-brown frass. Frequently empty brown pupa cases can be found around the base of damaged trees, either at the head of the larval gallery or in the soil close to the tree trunk.