Tree diseases are part of tree ownership. If you don’t have your trees checked and treated, the tree can make the rest of your yard get sick. To know when something is wrong, you have to know what everything looks right. There are a few different things homeowners can do to check their trees, but the most important thing is to just pay attention. In Ontario, there are plenty of diseases out there, and we have written this piece to explain 3 of them today:
1. Beech Bark Disease
Beech bark disease (BBD) is a devastating disease of American beech (Fagus grandifolia Ehrl) caused by a combination of damage to the bark and vascular tissue by the beech scale insect (Cryptococcus fagisuga), followed by infection with several fungal species (Neonectria naginata, Neonectria Santissima, and Bionectria ochroleuca).
Beech Bark Disease was only recently discovered in Southwestern Ontario, but it poses a major threat to all beech trees in the area.
Trees Affected
- All species of beech trees
Signs & Symptoms
- Discoloured and missing scales
- Brown slime oozing from the dead bark
- Leaves that do not reach their full size or colour
Disease Cycle
Neonectria ditissima and N. faginata produce ascospores in the late summer or autumn. Neonectria cankers can be found on other hosts throughout the range of American beech and opportunistically infect the wounds caused by beech scale, but are not actively vectored by it. New infections are initiated in the autumn, almost always from ascospores. Neonectria spp. can have an asexual phase in the summer that produces conidia in pinkish cushions called sporodochia, but it is not known what role conidia play in disease spread. Both ascospores and conidia are windblown and will cause infection if they reach susceptible plant tissue. Tarry spots can be a symptom of infection with Neonectria spp. and sometimes perithecia will form around these spots.
Management
- Application of insecticides or insecticidal oils when crawlers are still present.
- Selective harvesting to remove diseased beech trees can salvage trees before they fall, and may reduce the levels of beech scale, to allow resistant or partially resistant trees a better chance of survival.
- Minimizing root disturbance and by use of herbicides and brush cutting, to encourage more desirable species, like maples and oaks.
2. Tar Spot Disease on Maple Trees
Tar spot is a fungal leaf disease that does occur on several plants, but it is most common on maple trees. It does not cause permanent damage to the tree.
Trees affected
- Red maple
- Norway maple
- Silver maple
Tar spot also affects willow and tulip trees.
Signs & Symptoms
- It starts with small yellow spots on growing leaves, and by late summer these yellow spots expand into large black blotches that look like tar has been dropped on the leaves.
Disease Cycle
It starts with small yellow spots on growing leaves, and by late summer these yellow spots expand into large black blotches that look like tar has been dropped on the leaves. This is because a fungal pathogen, Rhytisma acerinum has developed on the leaves of the maple. When the fungus initially infects a leaf, it causes a small 1/3 cm (1/8 inch.) wide yellow spot to form. As the summer weather progresses, that spot spreads, eventually growing up to 2 cm (3/4 inch.)
wide.
Management
- Proper garden and yard sanitation will help reduce the spread of tar spots.
- Overwintering in fallen leaves, one of the best practices is the removal of all your maple’s fallen leaves and bagging or composting them to eliminate the closest source of tar spot spores. If you leave the fallen leaves on the ground until spring, the spores on them will likely reinfect the new foliage and start the cycle again.
- Young trees may require treatment, especially if other trees have had a lot of their leaf surfaces covered by fungal disease in the recent past. If you’re planting a younger maple in an area prone to the fungal disease, though, applying a fungicide, Safer Defender Garden Fungicide 1L Ready-to-Use or Safer 3-in-1 Garden Spray 1L Ready-to-Use, at bud break and twice again in 7- to 14-day intervals is recommended. Once your tree is well-established and too tall to easily spray, it should be able to fend for itself.
3. European Gypsy Moth
The European Gypsy Moth has been affecting trees in Southwestern Ontario for over 20 years. The larva stage of the moth eats the leaves of multiple kinds of trees, making them a target for other diseases and damage, and, eventually, death. However, identifying this tree disease is much easier than other diseases as the affected trees lose their leaves, and caterpillars crawl everywhere around them.
Trees Affected
- Oak
- Birch
- Poplar
- Willow
- Beech
- Cherry
- Maple
- Apple
- Basswood
- Elm
Signs & Symptoms
- Visible egg masses: covered with buff or yellowish hair from the abdomen of the female and averages about 1-1/2 inches long and about 3/4 of an inch wide.
- Visible caterpillars: newly hatched caterpillars are black and hairy. Later stages of the larvae develop a mottled yellow to grey pattern with tufts of bristle-like hairs and a distinctive colour pattern of five pairs of blue dots followed by six pairs of red dots along their backs.
- Visible adult moths: male moths are brown with a darker brown pattern on their wings and have a 1-1/2-inch wingspan. Females are slightly larger, with a two-inch wingspan, and nearly white with dark saw-toothed patterns on their wings.
- Defoliated trees
Disease Cycle
Gypsy moths have four stages of life: egg, larva or caterpillar, pupa, and adult moth. Females lay a mass of 500 to 1,000 tan, fuzzy eggs in a sheltered area. The eggs remain here over the winter and hatch when the hardwood trees bloom in the spring. Once hatched, larvae feed for seven to eight weeks, pupate in a protected area for two weeks, and emerge in moth form, when they will mate and start the cycle over.
Management
- Early identification is imperative for the successful control of Gypsy Moths. Trapping helps identify the moths and monitor their spread to new regions. Gypsy Moth Traps are specific in shape and require that a pheromone be used as an attractant.
- Physical controls like sharp blasts of water and physical wiping of the egg masses can be used to remove them. Tree banding after eggs have hatched reduces Gypsy Moth caterpillar’s ability to reach foliage and can drastically reduce damage symptoms. This is done by wrapping either burlap folded over itself or tape with adhesive applied around the tree trunk.
- Introduce Trichogramma Wasps as moth egg parasites early in the spring to help reduce egg populations. This can be effective to reduce the number of damaging caterpillars hatching, but should not be relied upon for full control.
- Spray Horticultural or Dormant Oils onto egg masses where visible in the fall and winter to reduce hatch rates during the following season.
- Maintain proper watering and feeding schedules for target trees to boost the tree resistance to pests and reduce the number of eggs being laid.
- Insecticidal sprays containing Bacillus thuringiensis kurstaki (Btk) can be used to help control the caterpillars as they feed. Btk sprays are most effective against young caterpillars as older ones tend to be more resistant to the bacillus.
It is important to take care of the trees on your property, as they are a crucial part of improving the greater local ecosystem by providing shelter and food for wildlife in the area. To prevent these diseases from affecting your trees, you should do plenty of research on the best trees to plant in your area.
If you think one of your trees may be affected by one of the common tree diseases listed above, you must take action to cure the tree of the disease or have it removed if the tree is too far gone.
