Brown Spot Needle Blight

Disease name: Brown spot needle blight

Pathogen name:Mycosphaerella dearnessii (syn. Scirrhia acicola). (fungus)

Hosts: Brown spot needle blight is a fungal disease most commonly found on Austrian pine (Pinus. nigra), eastern white pine (P. strobus), ponderosa pine (P. ponderosa), and Scots pine (P. sylvestris).

Symptoms

Brown spot needle cast symptoms develop in late summer. They start as gray-green spots on the needles. The spots can enlarge to become bands around the needles. The portion of the needle beyond the band dies.

By late autumn, many of the needles die completely and fall off. Not all the needles will fall off at this time; some may still be seen on the tree in spring.

Symptoms often develop first on the lower branches of the tree.

Smaller, younger trees are often more seriously affected.

Disease Cycle

Brown spot overwinters as oval-shaped fruiting bodies in infected and dead needles, but also as vegetative mycelium in infected needles.

New spores are produced in wet weather during spring, with spore production continuing through the summer. These spores will infect the current season’s needles.

Vegetative mycelium spreads through the infected needles and by late summer new fruiting bodies will develop in dead needles.

Management

Cultural Management

Avoid pruning wet trees. Pruning wet branches can potentially spread the fungal spores.

Keep trees mulched and watered during drought periods. Reduction of stress is a valuable tool in helping plants resist disease problems.

Severely infected limbs, as well as all needle litter from the ground, should be removed and destroyed to prevent spreading the disease.

When planting new trees, space them appropriately so that there is good air circulation around them.

Chemical Management

Fungicides are available for management of brown spot needle blight.

The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.

For current pesticide recommendations, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.

Diplodia

Disease name: Diplodia tip blight (formerly known as Sphaeropsis tip blight) (fungus)

Pathogen name:Diplodia pinea (syn. Sphaeropsis sapinea)

Hosts: Diplodia tip blight is a common fungal disease of pines with needles in bunches of 2’s and 3’s. Austrian pine (Pinus nigra) is the most susceptible host, although the following pines are also susceptible: Scots pine (Pinus sylvestris), red pine (Pinus resinosa), Mugo pine (Pinus mugo), and Ponderosa pine (Pinus ponderosa).

Pines with needles in bunches of 5 are highly resistant. The disease can attack other conifers such fir, spruce and juniper, but generally does very little harm to these species.

The disease is more common on trees older than 15 years of age (trees that are more stressed), and most severely damages trees that are older than 30 years.

It is seldom seen in forests but is common in landscape trees stressed by poor sites, drought, hail or snow damage, over shading, compacted soils, root restrictions, insect activity, or other mechanical wounding.

The fungus affects current year shoots and sometimes branches, and can disfigure or even kill them under severe conditions.

Symptoms

Diplodia tip blight kills needles at the tips of branches. Symptoms often start on the lower half of the tree and progress upwards. When the new needles (candles) are expanding, they become stunted, turn yellow, and then turn tan or brown.

Generally all needles on the current season’s shoot are killed. Often resin droplets from cankers are seen on the dead shoots.

During summer and fall, black fungal fruiting bodies will appear at the very base of the needle under the fascicle (sheath). The fruiting bodies may also be seen on the scales of second year seed cones and on infected bark.

As lateral shoots are killed, whole branches may die back to the trunk and the tree becomes disfigured.

This disease can also form perennial cankers that can cause branch death.

Disease Cycle

The diplodia fungus overwinters as fruiting bodies in infected shoots, bark, and seed cones. Tiny spores erupt from them in wet weather.

Although they are produced from spring to early fall, they are especially abundant in spring and early summer, when the new shoots (candles) are expanding.

Candles can only be infected by the fungus while they are elongating in the spring. After the needles have fully expanded, the shoot can no longer be infected by the fungus.

Wind and rain disseminate the spores.

When the spores land on a susceptible plant part, they infect it by penetrating the plant through wounds or stomates (breathing pores). Once the fungus penetrates the plant, it quickly spreads throughout the needles, then to the stem and into nearby needles.

The needles begin to die several weeks after infection.

Later in fall after the needles have died, the fruiting bodies appear on the base of the needles or on second year seed cones.

Management

Cultural Management

To help prevent infection from diplodia tip blight, maintain tree health, as the disease is more severe on trees that are under stress.

Keep the tree watered during dry periods. Maintain a layer of mulch under the tree to conserve moisture.

Because the fungus can also infect wounded tissues, avoid pruning trees from late spring to early summer when they are most susceptible.

Since cones and dead tips contain the fruiting bodies, when feasible, remove and destroy all infected cones and dead and dying branches during dry weather.

Pruning tools should be disinfected between cuts.

Chemical Management

There are fungicides available to treat diplodia tip blight. The first treatment should be done at budbreak. Additional treatment should be applied according to label directions.

The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.

For current pesticide recommendations, contact The Morton Arboretum Plant Clinic (630-719-2424 or plantclinic@mortonarb.org).

Dothistroma Needle Blight

Disease name: Dothistroma needle blight

Pathogen name:Dothistroma septosporum (syn. D. pini) (fungus)

Hosts: Dothistroma needle blight is a fungal disease of a variety of pines, especially Austrian pine (Pinus. nigra), mugo pine (P. mugo), ponderosa pine (P. ponderosa), red pine (P. resinosa), and Scots pine (P. sylvestris).

Symptoms

Dothistroma produces yellow to tan spots on the needles. These will enlarge to form dark reddish bands on the needles in the fall. The ends of the needles beyond the bands die, while the bases of the needles remain green. Small black spots may appear in the dead and discolored areas.

Needles shed prematurely, especially second-year needles.

Infection is usually worse in the lower half of the tree.

Successive years of severe infection result in decreased growth and death.

Disease Cycle

Dothistroma overwinters as fruiting bodies in infected needles. In spring, the fruiting bodies will increase in size and break through the epidermis (outer skin) of the needles to release spores.

The germinating spores enter the needles through their stomata (breathing pores).

Not all infections occur in spring. Infection of older needles can occur throughout the growing season, approximately May through October.

As infected needles die, more fruiting bodies are produced under the epidermis of the needles.

Management

Cultural Management

Avoid pruning wet trees. Pruning wet branches can potentially spread the fungal spores.

Keep trees mulched and watered during drought periods. Reduction of stress is a valuable tool in helping plants resist disease problems.

Severely infected limbs, as well as all needle litter from the ground, should be removed and destroyed to prevent spreading the disease.

When planting new trees, space them appropriately so that there is good air circulation around them.

Chemical Management

Fungicides are available for management of Dothistroma.

The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.

For current pesticide recommendations, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.

Lophodermium Needle Cast

Disease name: Lophodermium needle cast

Pathogen name:Lophodermium seditiosum (fungus)

Hosts: Lophodermium needle cast is a fungal disease commonly found on Scots pine (Pinus sylvestris), red pine (P. resinosa), ponderosa pine (P. ponderosa), and Austrian pine (P. nigra).

Symptoms

In early spring, brown spots or bands with yellow halos appear on the previous year’s needles. As the season progresses, these spots enlarge, and the entire needle turns yellow and becomes brown by late spring.

Dead needles will begin to fall in summer and continue to do so throughout the season.

Defoliation is common on lower plant portions, often leaving only tufts of green current-season needles at the tips.

In late summer, small, black, football-shaped fruiting bodies appear as conspicuous protrusions on dead needles. The fruiting bodies have a characteristic lengthwise slit down the center.

The current season’s growth will not show damage.

Disease Cycle

Lophodermium overwinters in infected needles as vegetative mycelium, rather than as spores.

The fruiting bodies that will produce the spores do not develop until the early part of summer.

The spores are produced and spread from late summer into mid fall, about August through October. The current season needles become infected at this time, but symptoms will not be noticed until the following spring.

Management

Cultural Management

Avoid pruning wet trees. Pruning wet branches can potentially spread the fungal spores.

Keep trees mulched and watered during drought periods. Reduction of stress is a valuable tool in helping plants resist disease problems.

Severely infected limbs, as well as all needle litter from the ground, should be removed and destroyed to prevent spreading the disease.

When planting new trees, space them appropriately so that there is good air circulation around them.

Chemical Management

Fungicides are available for management of Lophodermium.

The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.

For current pesticide recommendations, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.

Pine Wilt

Disease name: Pine wilt disease

Name of causal agent: Bursaphelenchus xylophilus, (nematode)

Hosts: Pine wilt is a fatal disease. The most common hosts are Scots pine (Pinus sylvestris), Austrian pine (Pinus nigra), mugo pine (Pinus mugo), red pine (Pinus resinosa), and Japanese red pine (Pinus densiflora). The disease is uncommon on white pine (Pinus strobus).

Pine wilt disease is widespread in much of the United States, especially in the Midwest.

Symptoms

On pines infested with the pinewood nematode, the needles appear as an off-color grayish-green, turning yellow and, finally, brown. The tree dies rapidly after the needles turn color, usually within a few weeks or months.

The dry, brown needles remain on the dead tree, rather than falling off. They are held on by the resin produced by the tree.

Most deaths occur in late summer or fall. A tree that declines slowly is usually not suffering from pine wilt.

Disease Cycle

Pinewood nematodes cannot move from tree to tree on their own. They are carried from dying trees to living trees during the growing season by the pine sawyer beetle.

This beetle will visit dying trees to feed, mate, and lay eggs. The beetle will conduct most of its life cycle in the dying tree, and during that time, the tiny nematodes will move into the spiracles (breathing pores) of the beetle’s body. When the beetles emerge as adults, they will fly to healthy trees to feed on the bark.

As the beetle feeds on a healthy tree, the nematodes leave the beetle and enter the tree through the feeding wounds. The nematodes will then infest the resin canals of the pine, multiply rapidly, and clog the water transport system of the tree.

The life cycle of the nematode can be completed in three to five days, so the population increases quickly.

The clogging of the water transport system of the tree by this large population of nematodes leads to the rapid death of the tree.

Management

A laboratory test to check for the presence of the nematode is necessary to confirm the diagnosis. The University of Illinois Plant Clinic will confirm pine wilt for a nominal charge. Some arborist companies have their own labs, or have access to other labs, and can assist with obtaining a proper diagnosis.

Cultural Management

Once a pine has started to die from pine wilt disease, it needs to be removed from the site immediately or burned where burning is permitted. The stump should be ground or buried. The wood should not be kept for firewood but can be chipped for use as mulch.

Chemical Management

Insecticide treatments to control the beetles that carry the nematodes are impractical because the beetle has a long period of activity. There are nematicides registered for management of the nematode. These products are for prevention, not cure, of pine wilt. They must be injected into the tree by a licensed professional before the tree is infested by the nematodes.

The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.

For current pesticide recommendations, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.