Apple scab


Scab may occur on leaves, fruit, leaf and fruit stems, and green twigs. Infections of the leaves and fruit are most common and obvious. Early season infections usually occur on the underside of the blossom cluster leaves because these are the first tissue surfaces to emerge from buds in the spring. Once the cluster leaves have unfolded and terminal leaves begin to develop, infections become evident on the upper surface of the leaves. Individual infections appear as roughly circular, brown to dark olive-green spots (lesions), which often seem slightly fuzzy or velvety in texture. Lesions along the veins or margins often cause those regions of the leaves to distort or crinkle. Primary (ascospore) infections are usually limited to one or two distinct spots per leaf, whereas secondary (conidia) infections are often much more numerous. Secondary infections occasionally are so numerous that the entire surface of the leaf appears covered with scab.


A trunk injection with a systemic fungicide, either PHOSPHO-jet or Alamo in ornamental trees. PHOSPHO-jet inhibits fungal cells while eliciting a plant health response from the tree. PHOSPHO-jet will promote stronger, healthier tree cells, promote root development and trigger the tree's natural defense mechanisms to make the tree more resistant to infection and better able to recover. Alamo will have more direct and aggressive activity against the fungus itself and is recommended if infection is chronic or particularly severe. While Alamo is a more potent fungicide, it will not have the plant health benefits of PHOSPHO-jet.


Generally, the best seasons for injection are fall and spring, as uptake occurs when trees are transpiring. The environmental conditions that favor uptake are adequate soil moisture and relatively high humidity. Soil temperature should be above 40 degrees for injection. Hot weather or dry soil conditions will result in a reduced rate of uptake, so trees should be watered if applications are made when soil is extremely dry. If treating trees in the summer, inject in the morning for best results. If treating an established infection, Alamo is recommended as a first treatment, with subsequent treatments of PHOSPHO-jet as necessary.

Destructive Pests of New Jersey

Asian Longhorned Beetle

The Asian Longhorned Beetle is a destructive pest of trees, originally from China. It can be identified by alternating white bands on long brown/black antenna. The appearance of small holes on trees can be an indication of infestation. If you see this pest please contact the New Jersey agricultural Extension Service at the link above.

Dutch Elm Disease

Dutch Elm Disease is a fungus which affects the American Elm. Symptoms begin as wilting of the leaves which turn yellow, and eventuelly brown. Dutch Elm Disease is a result of the fungus infecting and clogging the vascular system (Pholem) of the tree. This prevents water movement to the crown causing the browning and yellowing of the leaves, as the tree wilts and dies. The disease is spread by the Elm Bark Beetle. Certain fungicides, when properly injected, are effective in protecting elm trees from infection, and must be repeated every one to three seasons. Elm trees should not be pruned during the growing season because sap oozing from wounds may attract the Elm Bark Beetle.

Bacterial Leaf Scorch

Bacterial Leaf Scorch is an incurable plant disease that has infected an estimated 39 percent of oaks statewide. There is no cure for Bacterial Leaf Scorch, but with proper management affected trees can often be maintained for many years.Infected trees will need to be pruned, to remove infected limbs, and in many cases may need to be removed.

Emerald Ash Borer

The larval stage of the Emerald Ash Borer bores holes into the trunk and serpentine feeding galleries which disrupt the flow of nutrients as they rise up the trunk from the roots to the crown via the phloem (the tree's vascular structures) just under the bark, which eventually results in the death of the tree.

Hemlock Wooley-Adelgid

Adelgids are small insects, related to aphids. The hemlock woolly adelgid sucks sap from the young branches which results in needle drop and branch dieback.

Birch Leafminer

Birch Leafminer is an invasive wasp which lays its eggs into the leaves. Once hatched, leafminer larvae consume the tissues between upper and lower leaf surfaces causing brown blotches.” Healthy trees can withstand occasional attacks by birch leafminer. Repeated attacks can result in the general decline and death of the tree over time by secondary pests such as fungi and the bronze birch borer.

Common Spring-Time Diseases of Woody Ornamentals in the Landscape

Landscape Plants Rated by Deer Resistance

Pine Bark Beetles

There are many species of bark beetles that infest conifers. Adults tunnel through the bark, mate and lay eggs in the phloem, under the bark,where the larvae develop. Adults develop from pupae and emerge by boring out through the bark. Multiple generations a year are possible.

Leaf Chewing Caterpillars

Caterpillars are the larval stage of moths and are among the most serious defoliators of trees. The eastern tent caterpillar is responsible for defoliating forest trees, as well as cherry, apple and other ornamental shade trees. Others include the gypsy moth, winter moth, spring and fall cankerworm, bagworm, clear wing borers, pine tip moth and tussock moth. Some moth larvae, such as tip moths and clear wing borers, feed inside the twigs, shoots or trunk of the tree and are virtually unseen.

Sudden Oak Death

Oak Wilt

Oak Decline

Red Oak Borer

Iron Chlorosis

Phytophthora Root Rot


Apple scab

Forest Health in New Jersey

Oak Diseases

Armillaria Root Rot