Grapevine stem blight, also known as grapevine canker disease, is a fungal disease caused by Cryptosporella viticola.
The disease primarily affects perennial grapevine canes and trunks, but it can also spread to young shoots, leaves and fruit. Severe infections weaken vine growth, significantly reduce grape yields and may eventually cause the death of entire vines. Due to its persistent nature and difficulty of control, grapevine stem blight is an important disease that requires careful monitoring and effective management.
1. How Does Grapevine Stem Blight Develop?
Understanding the disease cycle is essential for effective prevention and control. The development and spread of grapevine stem blight generally involve three stages.
1.1 Overwintering and Spore Release
During winter, the pathogen survives in the bark and woody tissues of infected grapevine canes and trunks. In the following growing season, particularly during May and June, rainfall and increased humidity promote the release of fungal spores.
These spores can spread through wind, rain splash, insects and agricultural operations, providing opportunities for new infections.
1.2 Infection and Disease Development
The fungal spores enter grapevine tissues mainly through wounds or natural openings. After infection, the pathogen spreads through the tissues between the phloem and xylem, eventually affecting the vascular system.
The pathogen may produce pycnidia (spore-producing structures) in infected tissues and continue spreading along the vascular bundles.
The incubation period is approximately 30 days, although visible symptoms may take one to two years to develop. As a result, the disease can persist in vineyards and cause recurring infections over two to three consecutive years.
1.3 Secondary Infection
During the rainy summer season, fungal spores can spread through rain splash and air currents, causing repeated infections.
Frequent rainfall, high humidity and poor vineyard ventilation create favorable conditions for disease development and spread.
2. Symptoms of Grapevine Stem Blight
Grapevine stem blight can affect canes, leaves, young shoots and fruit. Early identification is important for preventing further disease development.
2.1 Symptoms on Canes and Trunks
Early stage:
Reddish-brown to dark purplish-brown lesions appear on grapevine canes, often near the base of the plant. These lesions are slightly sunken and have clearly defined margins.
Middle stage:
As the disease progresses, the lesions expand into dark brown, spindle-shaped or oval patches. Longitudinal cracks may develop on the affected surface, giving it a fibrous appearance. Infected canes become brittle and are more likely to break.
When cut transversely, the infected woody tissue may show dark purplish-brown discoloration and decay. Shoots above the infected area become weak, while leaves may curl, turn yellow and gradually wither.
Late stage:
Severe infections may cause the death of major canes or entire trunks. Newly developed shoots may suddenly wilt and die approximately two weeks after emergence, sometimes while the surrounding foliage remains green. This is one of the characteristic signs of advanced infection.
2.2 Symptoms on Leaves and Young Shoots
When young shoots become infected, the leaves may rapidly turn yellow, with curled leaf margins.
Purple-black streaks may appear along leaf veins, petioles and tendrils.
On the underside of leaves, pale green to yellowish-brown circular lesions may develop, often with grayish-black centers. As the disease progresses, leaf veins may become necrotic, causing the leaves to wrinkle, dry out and eventually fall.
2.3 Symptoms on Grapes
Infected young berries may develop grayish-black lesions on their surfaces, affecting normal fruit development and bunch formation.
During the ripening stage, numerous small black spots may appear on the fruit. These spots may contain pycnidia, the fungal spore-producing structures.
The symptoms can resemble those of grape ripe rot or other fruit diseases, but infected berries may be more susceptible to decay.
3. Effective Control Measures for Grapevine Stem Blight
Effective disease management requires an integrated approach combining agricultural practices, chemical protection and biological control.
3.1 Agricultural Management
Agricultural management is the foundation of long-term disease prevention. Maintaining healthy vines and reducing sources of infection can significantly lower disease pressure.
1. Vineyard Sanitation and Removal of Infected Materials
After autumn pruning, carefully remove infected canes, diseased fruit and fallen leaves from the vineyard.
Collect and properly dispose of infected plant materials through approved methods, such as deep burial or destruction where permitted. This helps reduce the amount of fungal inoculum surviving through winter.
2. Soil Improvement and Balanced Fertilization
Apply well-decomposed organic fertilizers, such as compost or mature cattle manure, to improve soil structure and promote healthy root development.
Adopt a balanced fertilization program based on soil and plant nutritional requirements. Avoid excessive nitrogen application, which can promote vigorous but weak shoot growth and increase susceptibility to disease.
3. Proper Pruning and Canopy Management
During winter pruning, retain healthy and vigorous canes while removing diseased or severely weakened plant parts.
Avoid excessive pruning that may create unnecessary wounds. During the growing season, remove overcrowded and excessive shoots to improve air circulation and sunlight penetration.
A well-managed canopy helps reduce humidity and unfavorable conditions for fungal development.
4. Frost Protection and Prevention of Mechanical Injuries
In northern grape-growing regions, appropriate winter protection, including soil covering where necessary, can help prevent frost damage to vines.
During pruning, tying and other vineyard operations, handle canes carefully to minimize mechanical injuries. Wounds can provide entry points for fungal pathogens.
3.2 Chemical Control
Chemical protection can help reduce fungal infection, particularly during periods when environmental conditions favor disease development.
The following treatments are referenced in traditional disease-management recommendations. Product selection, application rates and timing should always comply with local pesticide registration requirements and the manufacturer's label.
1. Dormant-Season Treatment
Before bud break, apply a lime sulfur solution at 5° Baumé or a 50% chlorobromoisocyanuric acid wettable powder at 750-fold dilution, where locally registered and approved.
These treatments are intended to reduce overwintering pathogen populations on vine surfaces.
2. Preventive Protection During the Growing Season
Before the rainy season, particularly during May and June, apply Bordeaux mixture at a 1:0.5:200 ratio or 75% chlorothalonil wettable powder at 600-fold dilution, where permitted.
Pay particular attention to protecting perennial canes that are two years old or older, as these tissues are more likely to harbor existing infections.
3. Treatment at the Early Stage of Disease
For localized infections on older canes, carefully remove diseased bark and affected tissue where appropriate. Apply a suitable registered wound-protection treatment to the affected area.
The original recommendations include 5% Junduqing at 30–50-fold dilution or Fubiqing at 10-fold dilution. These are product-specific names and should be verified against locally registered formulations before use.
For young shoots showing early symptoms, the original recommendations include:
85% fungicide wettable powder formulation at 750-fold dilution.
42.8% fluopyram + trifloxystrobin suspension concentrate at 1,500-fold dilution.
Where these active ingredients and formulations are registered for grapes and the target disease, applications may be made at intervals of 10–15 days, with two to three treatments as appropriate.
Always follow the product label for crop safety, application intervals, maximum application frequency and pre-harvest intervals.
3.3 Biological Control
Biological control offers an additional approach to integrated disease management and may help reduce reliance on conventional chemical fungicides.
1. Application of Beneficial Microorganisms
Research has indicated that certain beneficial microorganisms, particularly Trichoderma species and Bacillus species, can suppress some plant-pathogenic fungi.
Depending on the formulation, these microorganisms may be applied through soil treatment, root-zone application or suitable trunk and cane treatments.
Their effectiveness depends on the specific strain, application method and environmental conditions.
2. Induced Plant Resistance
Plant defense responses may also be stimulated using resistance-inducing substances.
For example, salicylic acid at 0.1% or chitosan oligosaccharide at 0.5% has been suggested in some disease-management recommendations to help activate the plant's natural defense mechanisms.
Use only products approved for the intended application and follow the recommended dosage and instructions.
4. Conclusion: Prevention Is the Key to Managing Grapevine Stem Blight
Grapevine stem blight is a persistent fungal disease that can seriously affect vine health, fruit production and vineyard profitability.
Because the pathogen can survive in infected woody tissues for extended periods and symptoms may take considerable time to become visible, relying solely on curative treatments is often insufficient.
An effective management strategy should focus on prevention and integrated control, including:
Regular vineyard inspection and early disease detection.
Timely removal and proper disposal of infected plant materials.
Balanced fertilization and improved soil management.
Scientific pruning and better vineyard ventilation.
Preventive fungicide applications during high-risk periods.
Appropriate use of biological control agents and plant resistance inducers.
By combining these measures and maintaining consistent vineyard management practices, growers can reduce disease pressure, protect vine health and support stable, sustainable grape production.
Early prevention, scientific management and integrated disease control are essential to keeping vineyards healthy and productive.
