Pine Blight
Pine Blight
Pine blight refers to a general term for multiple diseases with the common name of pine blight, as well as white pine blister rust, Dothistroma needle blight, and Sirococcus shoot blight. Pine blight diseases can be fatal to pine trees and can be damaging overall, especially in places where pines are prevalent in the environment, such as Eastern Ontario. Below is a summary of how these diseases show up, how to treat them, and how to prevent them.
White Pine Blister Rust (Cronartium ribicola)
How It Appears:
- Needle Symptoms: Initially, white pine blister rust only affects the needles of white pines, causing them to turn yellow or orange. The colored areas develop into brown spots that eventually become necrotic.
- Cankers on Branches: The disease creates cankers (swollen, sunken areas of bark) where branches meet or the main trunk. Cankers form by the fungus grows beneath the bark and cutting off the tree’s vascular system.
- Orange Structures: In the advanced stages, small, bright orange blister-like structures appear on the cankers in the summer, which indicate the presence of fungal spores.
Treatment:
- Pruning: Pruning can be effective if an infection is caught early enough. Remove the infected/dead branches and dispose of the infested materials appropriately to slow disease spread.
- Fungicides: Fungicides can be effective to slow the spread of white pine blister rust, and are typically most effective when trees are treated to stop the infection prior to becoming uncontrolled. Fungicide applications are typically done in late spring or early summer when the tree puts out the spores.
- Removal: If the severity of the infection is great, particularly where it occurs in commercial or otherwise valuable landscapes, removal of the infected tree may be the only feasible method for slowing disease spread and preventing further infection.
Prevention:
- Plant Resistant Varieties: Some species of pine are more resistant to white pine blister rust than others, and planting resistant varieties can reduce infection risk.
- Control Alternate Hosts (Ribes): The disease requires Ribes (currant and gooseberry bushes) as alternate hosts. Removing Ribes nearby will break the whole infection cycle.
- Continuous Monitoring: Continuously monitor your pine trees’ white pine blister rust symptoms, because if you can identify this disease early, then you may be able to minimize damage.
Dothistroma Needle Blight (Dothistroma septosporum)
What It Looks Like:
- Yellowing and Browning of Needles: One of the first signs of Dothistroma Needle Blight is the development of yellow or orange bands on the needles, generally either at or near the tips of the needles. The tips of infected needles turn brown, and the blight advances down the needle.
- Needle drop: With the disease progressing, ever so often, the infected needles drop prematurely, leaving the tree only a few remaining green portions. In extreme cases, some trees may have no needles on the entire crown.
- Tree decline: Eventually, multiple infections lead to crown thinning, stunted growth, and overall tree decline.
Treatment:
- Pruning Infected Needles: It is advisable to prune out any infected needles only on a dry sunny day to limit the further spread of the disease from tree to tree. The act of pruning greatly limits the fungal load and will increase tree health.
- Fungicide Applications: Fungicides have been used to help control and limit the spread of Dothistroma Needle Blight. Fungicides can be applied in the spring (most effective in early spring before bud burst or just before needles are infected).
- General Health of Tree: Provide proper amounts of water, nutrients, and mulch to increase the vigor of the tree. It is important to improve tree vigor to allow recovery and subsequent resistance to new algal infections.
Prevention:
- Proper Spacing and Air Circulation: Pine trees need to be well spaced so as to allow adequate air circulation around them. Overcrowding of the trees gives rise to a wetter condition, which allows easier disease spread.
- Avoid Overhead Watering: Do not use top watering methods, as dripping needles create conditions that promote the growth of fungi. The base of the tree needs to be watered instead of water from above.
- Keep Tree Vigor: Well-nourished trees develop more robust immunity against diseases. Providing constant fertilization and sufficient water in dry periods will keep your pine trees healthy.
Sirococcus Shoot Blight (Sirococcus conigenus)
How It Presents:
- Blackened Shoot Tips: The infection usually occurs in the new shoots of the pines, making them turn black and die. This is particularly evident during spring and early summer.
- Needle Yellowing and Curling: The shoots infested by the insect can also develop needle yellowing, curling, and early needle fall. Such symptoms result in dieback of the infested portions of the tree.
- Branch Cankers: With the development of the disease, small cankers will develop on the branches. The cankers may expand and cover larger portions of the tree.
Treatment:
- Pruning Infected Growth: Pruning of infected growth early in the growing season controls the spread of the disease and improves the health of the tree.
- Fungicide Applications: Fungicides could be applied to manage Sirococcus Shoot Blight if the blight is widespread. These would have to be done to the tree at the time of spore release in early spring.
- Tree Care: Equally to other pine diseases, maintaining the health of the tree through frequent watering, mulching, and fertilization will improve its resistance against Sirococcus blight.
Prevention:
- Avoid Overcrowding: Provide enough space between trees to reduce the humidity and improve air circulation.
- Remove Infected Material: Clear up and remove dropped infected needles and shoots. This minimizes the risk of reinfection.
- Prune in Dry Conditions: When you are pruning, make sure you do it under dry conditions. Wet weather causes the disease to spread very fast.
General Tips for Protecting Pines from Blight Diseases
- Regular inspection: Too early signs of the disease, inspect ordinary pine trees, especially during the spring and summer months when disease-causing fungi are most active.
- Proper water and fertilization: Place the pines well in water (especially in dry periods) and fertilize with a balanced, slow-release fertilizer to ensure healthy growth and improve resistance to diseases.
- Improve air circulation: Proper spacing between the trees and dilution of the dense leaves. Improve the air flow around the tree, reduce the moisture level, and reduce conditions favorable for the development of the fungus.
- Remove dead or infected material: Clean the fallen needles and branches immediately. The infected material can act as a breeding ground for fungal spores.
- Consider Fungicide Treatments: In high-risk areas, or if it is known that it is known to be present, consider applying fungal remedies as a preventive measure, especially in the early stages of development of the new shoot.
Conclusion
Among these challenges is pine blight. Effective management of the disease involves proper treatment during pruning, the application of approved fungicides, early detection, and regular maintenance. Proper tree care and sanitation lower these risks further. Such measures ensure that the blight diseases do minimal damage to the pine trees, keeping them healthy and flourishing.