Anthracnose is a common fungal disease that affects a wide variety of plants, including fruits, vegetables, trees, and ornamentals. It is caused by different species of fungi in the genus Colletotrichum. Anthracnose can be a destructive disease, causing significant losses in crop yield and quality. However, with careful monitoring and proper treatment, it is possible to manage anthracnose effectively. This comprehensive guide provides information on identifying, treating, and preventing anthracnose to help you protect your plants.
Identifying Anthracnose
Knowing how to accurately identify anthracnose is crucial for effective management. Here are the main signs and symptoms to look for:
On Leaves
- Small, irregular, brown lesions that often have a yellow halo or border. Lesions may merge and cause significant leaf necrosis.
- On some hosts, distinctive dead areas bounded by leaf veins, resulting in a shot-hole appearance as diseased tissue drops out.
- Severely infected leaves may turn yellow, wither, and drop early.
On Stems and Petioles
- Elongated black cankers or stem rot.
- Stem girdling and dieback may occur in some hosts.
On Fruits and Vegetables
- Sunken, dark brown or black lesions. Lesions may be circular or irregularly shaped.
- Lesions can enlarge rapidly and cause rotting of fruit.
- Hard, dark colored decay lesions beneath the skin of certain fruits like apples and pears.
On Flowers and Buds
- Flowers and buds may blight and drop prematurely.
General Signs
- Wilting and stunting of shoots and leaves may occur when stems are girdled or cankered.
- White spore masses may form on dead tissue during certain weather conditions.
- Premature leaf drop, bud drop, and fruit drop.
Key Identification Tips
- Look for the characteristic lesion shapes and colors – small, angular brown spots often with a halo/border.
- Check both sides of leaves for lesions.
- Inspect stems, buds, flowers and fruits as well as leaves.
- Monitor during cool, wet periods when symptoms are likely to show.
- Compare symptoms to photo guides to aid identification.
- Take samples to diagnostic labs for fungal culture if unsure.
Correct identification is important to distinguish anthracnose from similar issues like bacterial blights, environmental leaf spots, insect feeding damage and chemical phytotoxicity. Consult diagnostic services if uncertain.
How to Treat Anthracnose
Once identified, anthracnose can be managed using an integrated approach combining cultural practices, fungicides, and biological controls as needed. Key treatment methods include:
Sanitation
- Regularly collect and destroy infected plant material and debris to reduce inoculum.
- Disinfect gardening tools, pots and equipment between uses.
- For crops, plow under crop residues after harvest to promote decay of fungal spores.
Pruning and Thinning
- Prune out infected twigs, shoots and small branches.
- Thin dense growth to promote good air circulation and rapid drying.
- Prune so there is good penetration of sprays into foliage.
Fungicides
- Apply appropriate fungicides like chlorothalonil, copper, mancozebs or strobilurins.
- Ensure full coverage of both sides of leaves and all plant parts.
- Follow product labels for rates and timing of applications.
- Rotate between fungicide classes to prevent resistance.
Biological Control
- Apply fungal antagonists like Trichoderma species to help suppress anthracnose fungi.
- Introduce beneficial insects that prey on anthracnose spores like lady beetles.
Host Resistance
- For crops, plant anthracnose-resistant cultivars when available.
Balanced Nutrition
- Avoid excess nitrogen fertilization which can encourage susceptible, succulent growth.
Timing of Treatment
- Treat promptly at the first sign of disease rather than waiting until severe.
- Make preventive fungicide applications before rainfall when risk is high.
- Repeat applications at 7-14 day intervals depending on product and conditions.
- Continue spray program until conditions no longer favor disease development.
How to Prevent Anthracnose
While treatment can help manage outbreaks, prevention is key to avoiding anthracnose issues in the first place. Various cultural and management practices help reduce disease risk:
Ensure Adequate Spacing
Allow adequate spacing between plants to promote good air flow and rapid drying of foliage. This helps create conditions less favorable for spore germination and infection.
Avoid Overhead Watering
Water at the base of plants rather than with overhead sprinklers. This prevents extended wetness on foliage that anthracnose fungi need for infection.
Disinfect Equipment
Clean and disinfect gardening tools, pots, stakes and other equipment to prevent spreading spores from plant to plant.
Promote General Plant Health
Use proper nutrition and irrigation practices to promote vigorous plant growth. Healthy plants are less susceptible to infections.
Monitor Conditions
Keep a close watch on weather patterns and Plant disease forecasts. This allows preventive fungicide applications right before periods of high anthracnose risk rather than waiting for symptoms.
Remove Alternate Hosts
Eliminate weeds and volunteers that can harbor anthracnose during seasons when main crops are absent. Removing these alternate hosts reduces initial inoculum.
Use Resistant Varieties
For crops prone to anthracnose, plant resistant varieties when available. Check for resistance information from seed companies or university cultivar trials.
Employ Crop Rotations
For annual crops, use a 2-3 year rotation to non-related crops to prevent build up of anthracnose fungi in the soil.
Apply Preventive Fungicides
Use anthracnose-specific fungicides like chlorothalonil as a dormant spray or when conditions favor disease development.
Scout Regularly
Frequently scout susceptible plants to detect issues early before they can spread. This allows prompt treatment before major damage occurs.
By integrating some of these preventive practices, it is possible to effectively manage the risk of destructive anthracnose disease in your garden or farm. Pay close attention to plant health, weather conditions favorable for disease, and early warning signs of infections. Prompt identification and treatment of outbreaks combined with sound preventive practices offer the best protection against anthracnose problems.
FAQs about Anthracnose Identification, Treatment and Prevention
What plants get anthracnose?
Many types of plants can be affected by anthracnose including fruits like blueberries, raspberries, strawberries, cucurbits, tomatoes and peppers. It also affects trees such as sycamore, oak, walnut, dogwood and maple, plus woody ornamentals like roses, camellias and cedars. Turfgrasses may also be impacted.
What does anthracnose look like on plants?
The lesions caused by anthracnose fungi have some characteristic appearances depending on the host. On leaves, small angular brown spots with yellow borders are common. On fruits and vegetables look for sunken black lesions. Hard, dark decay under the peel occurs on apples and pears. Dieback is common when twigs and shoots are infected.
Is anthracnose fatal to plants?
Anthracnose can definitely be fatal if infections are severe enough. The girdling of stems and extensive defoliation can kill small seedlings or cause dieback of branches. However, plants are more likely just severely weakened and have reduced vigor and yields depending on the extent of infection.
What are some organic ways to treat anthracnose?
Organic anthracnose treatments include removing and destroying infected material, using Bordeaux mix fungicide, applying neem oil, spraying hydrogen peroxide or potassium bicarbonate products, and introducing beneficial fungi like Trichoderma. Improving plant vigor through proper nutrition is also helpful.
How do you get rid of anthracnose spores?
Regular removal of infected debris destroys anthracnose spores rather than allowing them to persist. Pruning out cankered twigs also eliminates spores. Fungicide sprays are useful right before spore release. Spreading mulch under plants reduces soil splash dispersal of spores. Crop rotations or eliminating alternate weed hosts prevents carryover.
Is anthracnose treatable?
Yes, anthracnose is very treatable if caught early, though it is better prevented through good horticultural practices. A combination of fungicide applications, proper sanitation, resistant varieties, and methods to reduce leaf wetness duration can effectively treat outbreaks.
How do you stop anthracnose from spreading?
Stop anthracnose spread by thinning dense growth, removing and destroying infected plant parts, avoiding overhead irrigation, using fans to improve air movement, cleaning tools between plants, spraying protective fungicides, and monitoring closely for new symptoms after initial outbreaks.
What weather conditions favor anthracnose?
Cool, wet, rainy conditions favor anthracnose. Spores require sufficient moisture to germinate and penetrate susceptible tissue. Prolonged leaf wetness for 12 hours or more allows infection. Optimal temperature range is around 70-80 F.
Is anthracnose bacterial or fungal?
Anthracnose diseases are caused by fungal pathogens in the genus Colletotrichum rather than bacteria. Some common species involved are C. acutatum, C. gloeosporioides and C. graminicola, though many others exist that infect specific hosts.
Can anthracnose kill trees?
Severe anthracnose infections can definitely kill trees when main stems are girdled or weakened trees succumb to secondary pests. However, it more commonly results in leaf loss, dieback of twigs and branches which reduces growth, or development of cankers that damage but don’t kill trees outright.
Conclusion
Anthracnose is a destructive fungal disease affecting many types of plants worldwide. This guide covers key aspects of identifying, treating and preventing anthracnose to help you manage it effectively. Look for the characteristic lesion appearance on different plant parts and confirm by laboratory diagnosis if needed. Integrate fungicide sprays, sanitation, cultural practices and resistant varieties when treating outbreaks. Focus on preventive measures to avoid infections in the first place. With proper monitoring and action when conditions favor disease, it’s possible to avoid major anthracnose problems in your landscape, orchard or crops.