NEW ENGLAND'S COMMON
TREE AND SHRUB DISEASES
Some of the most common tree and shrub disease found here in New England are, but not limited to:
Anthracnose affects many different species of plants in Rhode Island. Many of these are popular to your yards, including ash, maple, oak, sycamore, and walnut. The symptoms of this disease primarily make their appearance in the spring. While the symptoms may be similar between the different tree species, these pathogens are host specific that infect only one tree species.
Anthracnose will over winter in twigs and smaller branches on the tree as well as in the dead fallen leaves. Mild winters allow this disease to be active and form cankers, which cause dieback of the infected branch or twig. As the spring comes around, the fruiting bodies (contains the spores) thrive on the dead wood and fallen leaves. These spores are released into the surroundings by wind, rain, and cool spring temperatures, conditions optimal for the Anthracnose. The disease's progress is only halted by the hot/dry temperatures of the summer months or by chemical means.
Cedar Rust infects trees and shrubs in the cypress family. Here in Rhode Island we will deal primarily with Cedar Apple Rust, Hawthorn Rust, and Quince Rust.
Apple Cedar Rust Apple Cedar Rust
Cedar Apple Rust has several hosts, such as Eastern Red Cedar and Juniper, Apple and Crab Apple trees. This disease becomes prevalent late summer to autumn, when galls are formed (combination of plant and fungus tissue), looking like green balls on the leaves. As these galls mature they grow up to two inches in diameter, and as the spring rains come they swell and extrude a bright orange gel. It is from this that the fungus spores appear and become infectious to surrounding apple/crab apple trees. These galls die after the first year and really cause little damage to the host, other than dieback from where the gall attached itself. The apple and crab apple trees on the other hand are easily infected, seen by the yellow-orange spots on the leaves early spring. These spots continue grow, turning more orange with reddish borders. Fringe-like structures then form in a ring pattern appear on the underside of the leaf about mid-summer. It is these structures that produce the spores which are infectious to junipers and the cycle continues.
The Hawthorn Rust is very similar to the Cedar Apple Rust, with one major difference being that the galls can produce spores for three to five years. This can also cause moderate to severe dieback of the twigs which the galls are attached to.
Quince Rust has been labeled as the most devastating of the three rust disease we have discussed, with most damage found on but not limited to apple, mountain ash, cottoneaster, hawthorn, pear, and flowering quince. Here in Rhode Island we would mostly see this disease in Hawthorns. This disease is also a perennial disease and over-winters, just as Hawthorn and Apple Cedar Rust. One of the most distinguishing characteristics of this disease is the formation of white tube-like structures about a 1/2" in length, that emerge from the cankers on twigs, branches, and fruit. The same bright orange gel oozes from these infectious spots and are easily spread to surrounding junipers.
Cytospora Canker of Spruces:
This is a common disease here in the Northeast and could be one of the most damaging diseases among spruces. This disease attacks Black Spruce, Colorado Blue Spruce, Norway Spruce, White Spruce, Douglas Fir, Balsam Fir, and Eastern White Pine to name a few.
A common symptom is the browning of needles on the infected spruce in the spring and early summer. You will see large amounts of white sap being extruded through cankers running down the tree trunk, along with white dry patches of sap resin on the trunk. The easiest way to identify this disease is to cut some of the bark away going from a non-infected area to an infected area. As you peel away the bark, there will be tiny black fruiting structures. Once again there will be the yellowish to orange spores. These spores will ooze from these infected areas during periods of rain during the spring and early summer. It is also worth mentioning that in controlling this disease, controlling any insect problems is a must as they assist in spreading this disease.
Diplodia Tip Blight on Pines:
Most commonly this disease is found among Austrian and Black Pines, along some other species of two and three needle pines, for example Red Pine and Scots Pine. This fungus is common in more mature pines that are suffering from drought stress, root restriction, and many other site specific problems.
Diplodia Tip Blight
This pathogen infects the current year's shoots. The needles expand to 1/2 to 3/4 of their orignal size turning yellow and brown as they die on the branch. If you look at the base of the needles there should be tiny black fungal fruiting bodies that emerge from the needles surface. If left unattended over several years, the ends of the affected branches will have a proliferation of shoots. If this disease is left unchecked, it will result in the death of the tree.
Diplodia Tip Blight
This type of Tip Blight is amplified by drought, injury (hail, lightening, improper pruning), and insect damage. Along with these amplifiers some needlecast diseases caused by other fungi may cause damage, leaving entry points into the tree's vulnerable core.
The Dogwoods of Rhode Island are most commonly plagued with Dogwood Anthracnose and Powdery Mildew, both of which All Island Landscape can treat with applications of fungicides. We also recommend starting a tree fertilization program that will help to drive these diseases away. Healthy trees that are not lacking in nutrients will have a stronger immune system.
The Dogwood Anthracnose symptoms are purple or tan blotches on the leaves and cause significant leaf and twig dieback. If not treated the tree can die within a couple of years and a replacement can be costly.
Powdery Mildew on Dogwoods
Another common fungal disease is Powdery Mildew, indicated by the white powdery blotches on the plant. This disease can cause stunted or distorted growth patterns of the branches, decreasing the aesthetic value of the tree. This disease will rarely cause death, but if left may contribute to its demise. These diseases thrive in cool, damp, and poorly ventilated areas of your property.
One of the solutions to these two diseases could be transplanting the tree to an area where air circulation is not a problem. Call All Island Landscape Inc. for a price quote for our Tree Spade Service or go to that page of our web site for more information.
Juniper Tip Blight:
Phomopsis Tip Blight and Kabatina Tip Blight can cause serious problems in certain species of Juniper, especially when grown in crowed or stressed situations. This disease is primarily found, but not limited to young plants.
Phompsis Tip Blight
Phomopsis Tip Blight, infects new growth and the succulent branch tips of Junipers; the more mature junipers build resistance to this. Small yellow spots first appear and then change to a dull reddish or brown color, which then turns gray with small gray lesions that surround the branch tips. In the lesions are where you find the small black spore-bearing structures that are released during wet rain weather .
Kabatina Tip Blight, is another fungal disease that affects young year old twigs. The disease is usually associated with some type of wound from either insect damage or a broke branch/twig. The disease is similar to Phomopsis Tip Blight, but is believed to occur in autumn with the signs not showing until the spring of the following year. The disease part of the branch first turns a dull green then to a reddish or yellow color. The same grayish lesions are present with small black fruiting bodies at the base of the discolored tissue. This brown foliage eventually drops from the tree in May or June, this disease can also be confused with winter injury.
Fungal leaf spot is one of the more common diseases that is found here in the Northeast, in particular Rhode Island. Rhode Island's cool wet weather, that is associated with coastal communities, is a great enviroment to host this disease. Fortuently, in most cases this disease results in more appearence damage then actualy physical damage to the plant.
Leaf spot on crabapples, for example, have small brown spots with purple borders that develop on the leafs surface following damp spring weather. Once this disease progresses the brown colored leaf spots turn grayish, causing a "frog eye" appearance. Leaf spot also causes black rot cankers on weakened limbs, in particular an injury that happened the previous winter. In any of these cases it is advised you have one of our arborists come out and prune the disease wood out of the tree. Remmeber that an affordable professional prunning of your tree far beats the cost of a replacement.
Oak Leaf Blister
Oak leaf blister commonly affects the red oaks and white oaks we have here in Rhode Island. The symptoms of this disease are blister like, circular bulges on the uppper leaf surface. As these blisters age they turn a yellow to brown color. Spores are produced on the upper leaf structure in mid-summer, which gives the leaves a powdery appearance. It is common for some of these leaf spores to be lodged in the bud scales where they over-winter for the following spring. The leaves over time will build-up a resitance to this disease, but may in some circumstances require All Island Landscape Inc. to treat with a fungicide.
Phyllosticta Leaf Spot
Phyllosticta leaf spot of maples affect numerous species of maples, particularly silver, red, Japanese and Amur maples. The symptoms are circular spots, tannish in color with reddish or purple borders. As the season progresses, black fruiting bodies of this fungus appear in the ringed lesions on the leaves. Along with a treatments on fungicide All Island Landscape Inc. reconmends a injection fertilization program to boost the immune system of your prise specimin plants.
Powdery mildew has most-likely affected most of your plants at one time or another, may be without you ever noticing it's affects. The fungi that causes powdery mildew does differ from plant species to plant species, though the appearance is pretty simular in nature. As with most diseases the prompt identification and control of powdery mildew can prevent severe damage to the plant.
The way to identify this disease is by the superfical white or gray powdery growth of fungus over the surface of the leaves, stems, flowers and or fruit. This disease will continue to grow and can infect the entire plant, in these cases treatment by All Island Landscape Inc. is advised imediately. You will see along with this powdery fungus, leaf curling and twisting, yellowing of the leaves, and eventulually brown dead leaves as the disease progresses. Even though this disease may not be fatal to your plants, powdery mildew can defoliate the plant leaving you with a unsightly landscape. A side note to this disease, if your roses do become infected flowering may not happen for that year.
Below is brief list of some woody plants that are most suseptible to powdery mildew:
The following is a list of some herbaceous plants you may find in your landscape:
Not every situation results in chemical applications, ask our technicians for your best solution.