Botryosphaeria Canker and Dieback

What is Botryosphaeria Canker and Dieback?

Botryosphaeria canker and dieback is a serious fungal disease affecting a wide range of woody plants. It is caused by various species within the fungal genus Botryosphaeria. It is particularly detrimental to stressed plants and can lead to severe dieback or even the death of the host plant.

Regions Impacted

Botryosphaeria canker and dieback are prevalent in many parts of the world, particularly in temperate and subtropical regions. Stressful environmental conditions like drought or extreme temperatures often exacerbate its spread.

Host plants

This disease has a broad host range, affecting numerous types of trees and shrubs:

Apple, arborvitae, ash, aucuba, azalea, barberry, beech, birch, black gum, buckeye, camellia, cherry, cherry laurel, chokecherry, cotoneaster, crab apple, crape myrtle, cypress, dogwood, Douglas fir, eastern red cedar, elm, euonymus, false cypress, fir, forsythia, giant sequoia, hickory, holly, honey locust, honeysuckle, hypericum, juniper, lilac, linden, magnolia, maple, mountain laurel, oak, pear, pecan, persimmon, Pieris, pine, pittosporum, poplar, privet, prunus, pyracantha, robinia, redbud, rhododendron, rose, serviceberry, spirea, spruce, sumac, sweet gum, sycamore, tulip tree, viburnum, walnut,  willow, wisteria, witch hazel, yew, zelkova.

What Causes Botryosphaeria?

Botryosphaeria canker and dieback is caused by fungi in the Botryosphaeria genus. These fungi commonly infect plants through wounds, natural openings, or areas of stress, such as cracks in the bark or pruning cuts. The fungi are opportunistic pathogens, meaning they are more likely to infect plants that are already stressed or weakened by other factors.

Here are some common causes and contributing factors:

Environmental Stressors

• Drought conditions
• Extreme temperatures (either hot or cold)
• Overwatering
• Salt stress from either soil or water

Mechanical Damage

• Improper pruning techniques
• Lawn equipment injuries
• Storm damage, such as broken branches

Nutritional Factors

• Improper fertilization (either too much or too little)
• Soil compaction affecting nutrient uptake

Inadequate Care

• Planting in poorly drained soil
• Lack of mulch or improper mulching which can affect soil moisture levels

Contaminated Tools

• Using pruning equipment that is not properly sterilized between uses can spread the fungi from one plant to another.

Understanding the contributing factors can help in implementing effective preventive measures. Reducing plant stress through proper care and avoiding unnecessary wounding can go a long way in preventing infection.

What are the Symptoms?

The symptoms of Botryosphaeria canker and dieback can vary depending on the host plant, but some common signs are generally associated with this fungal disease:

Cankers: The most distinct symptom is the formation of cankers, which are sunken, darkened areas on stems or branches. The cankers may ooze sap or resin.

Dieback: Branches and twigs may exhibit dieback, starting from the tips and progressing inward. In some cases, the entire branch may die.

Discolored Foliage: Foliage may turn yellow, red, or brown, often before premature dropping from the plant.

Reduced Growth and Vigor: Infected plants usually show reduced growth and may look stunted compared to healthy plants.

Wilting: Even with adequate water, you may notice wilting of leaves and young shoots, particularly if the canker has girdled the stem or branch, restricting water and nutrient flow.

Fungal Structures: You may see small fruiting bodies (pycnidia) forming on the surface of the cankers. These are the reproductive structures of the fungus and are often a black or dark brown color.

Splitting Bark: The bark around the canker may split or peel away, revealing the discolored wood underneath.

Early detection of these symptoms can be crucial for effectively managing the disease. Regularly inspecting your plants, particularly during the growing season and following any periods of environmental stress, will help you catch any developing issues before they become severe.

How to Control and Prevent Botryosphaeria?

Controlling and preventing Botryosphaeria canker and dieback involves a multi-pronged approach that includes cultural practices, chemical treatments, and sometimes biological controls. Here are some strategies:

Cultural Controls:

• Proper Watering: Keep plants well-watered but avoid waterlogged conditions, as stress can make plants more susceptible to infection.
• Good Sanitation: Remove and destroy affected plant material immediately. Do not compost it.
• Pruning: Remove infected branches by cutting at least a few inches below the visible canker. Sanitize pruning tools between cuts with a 10% bleach solution or rubbing alcohol.
• Plant Spacing: Make sure plants have adequate spacing to ensure good air circulation, which can help to dry out foliage and reduce the humidity that promotes fungal growth.

Chemical Controls:

• Fungicides: Protective fungicides can be applied, particularly during wet conditions or when new growth is emerging. Always read and follow label instructions.

Prevention:

• Resistant Varieties: Whenever possible, choose plant varieties that are resistant to Botryosphaeria and other common diseases.
• Avoid Overhead Irrigation: Watering at the base of the plant rather than from overhead can reduce the likelihood of fungal diseases.
• Regular Monitoring: Keep a regular check on plants, especially during warm, wet conditions, and at times when plants are stressed (e.g., drought, extreme temperatures).
• Soil Testing and Amendment: Ensuring your soil has the proper pH and nutrient levels can go a long way in keeping your plants healthy and more resistant to diseases.
• Stress Reduction: Since stressed plants are more susceptible to Botryosphaeria, aim to reduce plant stress through proper fertilization, watering, and planting in the preferred light conditions.
• Equipment Sterilization: Sterilize garden equipment, especially if it has come into contact with infected plant material, to prevent cross-contamination.
• Mulching: Use mulch to prevent soil-borne spores from splashing onto plants.

By employing these control and preventive measures, you can reduce the chances of Botryosphaeria canker and dieback affecting your plants and manage the disease more effectively if it does appear. Always consult local extension services or plant pathologists for the most localized advice.