Next, let’s examine the possibilities for treating an anthracnose infection.
Pruning and Sanitation
To stop the infection from spreading if you notice symptoms of infection, prune out as much of the afflicted plant tissue as you can. Trim off any infected branches and leaves, then collect them for disposal.
Although hydrangeas can typically withstand a fair amount of pruning, if you need to remove more than one-third of the plant, it might not survive.
A source of infection the following spring can result from the fungus overwintering in plant waste. Make every effort to stop this as well.
Under your hydrangea, gather up any fallen leaves or other plant debris and throw it away far from your plants. Ideally, you ought to dispose of it in the trash in a tied bag. Don’t compost any plant material that has been exposed to disease.
Make sure to clean your pruning shears after use with a solution of 70% rubbing alcohol or 10% bleach. While pruning, you might also want to think about cleaning your instruments between cuts or between plants to prevent further undesired spread.
What kind of fungicide treats anthracnose?
The majority of anthracnose fungus on landscape plants are found on the leaves and twigs. These fungi overwinter on deciduous trees on diseased twigs or decomposing leaf litter. The fungi create a large number of microscopic spores in the spring, which are dispersed by raindrops or irrigation water to new growth, where they germinate and infect leaves and twigs that have just sprouted. A subsequent generation of spores is produced from the diseased portions of fresh leaves if wet circumstances are present.
The fungus can grow year-round on leaves and twigs of irrigated evergreen species like the Chinese elm and coast live oak, but on most deciduous trees, the disease’s progression slows and eventually disappears in hot, dry conditions.
MANAGEMENT
Even though anthracnose is present, some cultivars of vulnerable landscape plants can still be attractive with proper care. In order to promote air circulation and boost sunshine, plant new plantings with cultivars resistant to the fungi that cause anthracnose.
Although there are certain pesticides available to prevent anthracnose infections, they cannot consistently control the illness. On Modesto ash, preventative measures have been proved to be most effective; see the Chemical Control section.
Anthracnose cannot be successfully treated if symptoms appear or become severe during a growing season.
In managing anthracnose, environmental conditions are also crucial. Keep an eye on current conditions like irrigation and rain to see if either encourages the growth of anthracnose. Weather in the spring that is dry may negate the need for disease management. A disease outbreak that can necessitate the use of control measures could be caused by a wet spring or an irrigation system that wets the foliage.
Avoid planting species that are especially vulnerable, such as several cultivars of the London plane tree, American sycamore, and Modesto ash (Fraxinus velutina ‘Modesto’) (Platanus x hispanica). The California sycamore (Platanus racemosa) is extremely vulnerable to anthracnose, which causes the tree to become deformed and seem twisted. Although trees often survive these attacks, they may momentarily lose apical control, which causes greater lateral growth and lower height. The cultivars Moraine, Raywood, and the Evergreen Ash (Shamel) are more anthracnose resistant than others in the ash family. Plant the more resilient Drake variety of Chinese elm as opposed to True Green or Evergreen. The relative vulnerability of several landscape trees to anthracnose is displayed in Table 1.
Depending on the local environmental circumstances and the intended pruning technique, consider whether anthracnose or powdery mildew resistance is more important when planting the London plane, commonly known as the plane tree; see Cultural Practices. For instance, the Bloodgood London plane tree cultivar is immune to anthracnose-causing but not powdery mildew-causing fungi. On the other hand, the powdery mildew-prone cultivar Yarwood is sensitive to anthracnose.
Pruning. Infected leaves, twigs, and branches should be pruned, destroyed, or buried in the fall or winter. For the majority of trees, severe pruning of bigger diameter branches is not a good idea since it results in bushy watersprouts that are weakly linked to the trunk and vulnerable to diseases like powdery mildew. After the leaves have opened and the spring rains have ended, fertilize trees that are seriously afflicted to encourage rapid development. Prevent irrigation systems from wetting the foliage.
Sanitation. During the growth season and in the fall, rake up fallen leaves and twigs and dispose of them. To improve airflow in the canopy and get rid of the dead and unhealthy twigs and branches from the previous season, prune throughout the winter.
Plants should be placed far enough apart to enhance air flow and sunlight, which, when trees are fully developed, help the leaf surfaces dry up more quickly.
Sycamores are frequently pruned. Trees that have undergone pollarding have all of the previous year’s growth removed. Pollarding, which removes all pathogen-infected shoots, is not advised for most trees but may be helpful for London plane trees to prevent anthracnose. However, pollarding encourages the growth of new shoots and leaves, which makes London plane trees more susceptible to powdery mildew. The cultivar Yarwood is a wise choice if you want to pollard London plane trees every year because of how resistant it is to powdery mildew.
On Modesto ash, a number of fungicides are available that inhibit anthracnose to differing degrees. Only healthy tissue is protected by fungicides, which leave behind persistent infections. Timing and full spray coverage are essential for disease prevention. Spray all new growth liberally as the spring buds start to open. Prior to wet seasons, apply pesticides. You can postpone this application if there aren’t any rains expected. Additional treatments would be needed at intervals of around two weeks to preserve new growth if damp weather is forecast.
The systemic fungicide thiophanate-methyl (e.g., Cleary’s 3336, for professional use only), copper sprays containing copper diammonia diacetate (e.g., Liquicop), propiconazole (e.g., Banner Maxx II), and protective fungicides containing chlorothalonil are the most effective fungicides for control. In Modesto ash, chlorothalonil and thiophanate-methyl provide the best control. Always adhere to label instructions.
Large, towering trees are challenging to completely cover; spraying is ineffective and may not be necessary or practical. While control may be possible in some circumstances, anthracnose can recur periodically, necessitating the continuation of a prophylactic spraying regimen. Fungicide treatments for anthracnose control often work well on ash, but their effectiveness on other species in California has not been shown.
What fungicide works best on hydrangeas?
Fungicides can be used, however the majority of home gardeners don’t think it’s a worthwhile strategy. By maintaining the area beneath the hydrangea free of leaf litter and occasionally removing the old stems to allow air to circulate within the plant, you can aid in the treatment of brown spot. Additionally, if your hydrangea has significantly flowered over the summer, picking off the dried blooms that are resting on the leaves may aid in improving air circulation.
Natural Treatment For Leaf Spot on Hydrangeas
Leaf spot on hydrangeas can be treated using several natural approaches. Among them is misting diseased leaves with:
- Grass Tea
- Water kelp
- Oil of garlic
- Alcohol Peroxide
Use these natural remedies according to the instructions on the bottle. Spray the leaves with a solution of 1 ounce of hydrogen peroxide and 8 ounces of water in a spray bottle.
To assist stop the spread of leaf spot, we also advise removing all sick and dead leaves from the plants.
Chemical Treatment For Leaf Spot on Hydrangeas
Late in the spring to mid-summer is the ideal time to apply fungicides. Chlorothalonil and thiophanate-methyl are the fungicides that work best on hydrangeas. Both of those aid in eliminating fungus brought on by cercospora and anthracnose. Use each bottle as specified on the label. Typically, 10 to 14 days are needed between applications. For more serious situations, you might apply more frequently.
How do I get rid of fungus on my hydrangeas?
Unfortunately, there are still more bacterial, viral, fungal, and even fungal illnesses that can harm the longevity, health, and look of your hydrangea. Let’s look at a couple of them.
Botrytis Blight Fungus (Botrytis cinerea)
How to recognize it: Botrytis Blight kills flower buds before they bloom by attacking them. The fungal infection can spread to the leaves below when the contaminated flower parts fall onto them. Typically, water-soaked patches on the blossoms are the first indication of this fungus. Then, lesions that seem reddish or brown.
How to treat or avoid it: Since Botrytis Blight prefers cool, moist environments, try your best to maintain low humidity levels, maintain excellent ventilation around them, and appropriately spacing your hydrangeas. Watering earlier in the day and focusing on the root rather than the blooms and leaves will also be beneficial. Make sure your pruning shears have been bleach-treated before using them to stop the spread of any existing diseases. Additionally, be sure to pick up any fallen, damaged, or dead flowers and foliage. Fungicides should be used to treat the fungus if it persists.
Anthracnose Fungus (Colletotrichum gloeosporioides)
How it occurs: Plants that have received a lot of fertilizer are in a dense fog or persistent rain.
How to recognize it: Large, brown spots that are irregular or circular in shape and lighter in color in the center start to emerge on hydrangea blooms and leaves.
Instead of misting the blooms and leaves, water the plant’s base to treat or prevent it. As soon as you notice any unhealthy leaves or blooms, you should clip them. Use a copper-based fungicide on the sick plant. Additionally helpful are liquid kelp, hydrogen peroxide, and garlic oil.
Bacterial Leaf Spot (Xanthomonas campestris)
How to recognize it: Water-soaked spots that are angular and darkened appeared on the leaves and flowers. As they spread, these blotches resemble lesions and start to kill off the leaves.
Treatment or prevention: Wounds and holes allow bacteria to penetrate the plant. If these are your hydrangeas, you can take action to keep bacteria from harming them by applying copper hydroxide (Kocide).
Tomato Ringspot Virus
How to recognize it: The hydrangeas’ leaves start to turn yellow, and the plant’s growth is subpar.
Nematodes carry this virus, thus treating or preventing it is important. Therefore, be sure to use nematode-free soil or a blend. You can treat your hydrangeas with a nematode repellant if they already grow in nematode-infested soil.
Why do the leaves of my hydrangea have dark spots?
The huge flower heads that bloom from spring through autumn make hydrangeas one of the most widely planted decorative plants. With many hydrangeas generating big, dense leaf formations, the foliage is also lovely.
The aesthetic of this well-liked plant can be ruined by black, purple, and brown patches on its leaves, which make it look sickly and detract from the attractiveness of the blooms.
The most frequent reasons for spots on hydrangea leaves will be covered on this page, along with solutions that include a number of suggested items.
Two Common Fungal Diseases That Affect Hydrangea Leaves
The two most prevalent fungi that harm hydrangea leaves are listed below, and both have symptoms that are extremely similar:
Leaf spot caused by Cercospora
This is a pervasive fungus infection that can harm numerous hydrangea plants. The initial signs of infection are likely to be dark or purple spots, frequently round, 3-6mm in size, dispersed on various leaf surfaces and on unrelated plants. Autumn is a common time of year for cercospora to appear on hydrangea leaves, and this is partly because of the moister weather.
Anthracnose 2
Although less often than Cercospora, Anthracnose also causes sizable brown, black, and purple spots on hydrangea leaves, most frequently on varieties with huge leaves, such macrophylla. The spots could have a bullseye in the middle and rings around them. In addition to being circular, they might also be angular. In contrast to Cercospora, Anthracnose patches may also be present on the blooms. Excessive fertilizer use, particularly in hydrangeas growing in pots, can make anthracnose more severe.
Risk to Hydgrangea Health
In the fall, Cercospora Leaf Spot is so prevalent that many gardeners decide to overlook it. The hydrangea plant is unlikely to succumb to the fungus this late in the year, and any fungus-related treatments won’t have time to take effect. Cercospora can limit plant growth, but it’s doubtful that it would cause the plant to perish.
While most occurrences of anthracnose do not result in hydrangea death, some do. It is a more serious condition than cercospora.
Both types of fungal infections can cause growth problems, limited photosynthesis, and damage to leaves.
Causes of Brown Spots on Hydrangea Leaves
The causes of brown hydrangea leaf spots and fungal diseases include the following:
- An environment where the leaves are wetter for longer and don’t dry out as rapidly can be produced by an extremely wet summer and autumn. This promotes microbial expansion, which subsequently multiplies rapidly. After a period of rainy autumn weather, it’s not unusual to observe brown fungal leaf infestations; at this time of year, even fog and morning dew can exacerbate the problem.
- The hydrangea’s placement should be taken into account because these plants require sufficient airflow for the leaves to dry out. If you plant the hydrangea close to a wall in a very shaded area of the yard, the leaves may start to develop fungus.
- One of the most frequent causes of fungal disease in hydrangea leaves is probably overhead watering. In addition to soaking the leaves, this also spreads the fungus, which causes the brown patches on the hydrangea leaves to spread and enlarge.
- Since moisture on the leaves won’t evaporate as rapidly at night and the leaf surface may be vulnerable to fungal growth and spread, hydrangeas shouldn’t be watered in the evening.
- When trimming hydrangeas, it is best to practice proper hygiene since fungal infections, which are frequently initially undetected, can spread via hands and secateurs.
SolutionsHow to Get Rid of Brown Spots on Hydrangeas
Here is a list of things you should do if you notice brown patches on your hydrangeas:
- Don’t be alarmed if you see a few brown spots on the hydrangea leaves after some damp weather in the late summer or early fall; this is natural. The common fungus pathogen can be found in most gardens and is just waiting for the appropriate season to flourish.
- Remove the leaves that are the most contaminated off the plant, and then discard them in the trash rather than the garden to avoid reinfecting the plant.
- Verify that the hydrangea is situated properly. Avoid spending time in extremely damp or poorly ventilated areas. It is advisable to move hydrangeas that are crowded by other plants and growing adjacent to walls.
- Remove a few stems from the hydrangea to improve ventilation if it is excessively dense from lack of trimming.
- To avoid water dripping onto the leaves and spreading the fungus to new plants, stop watering hydrangeas from above and switch to watering at ground level.
- Water in the morning rather than the evening to give the leaves time to dry before dusk.
- Remove any fallen leaves from the plant’s base on a regular basis because if they are allowed to rot in the soil, the fungus may spread to other parts of the plant.
- Always wash your secateurs after trimming hydrangeas with water and bleach, or give them a quick wipe with an alcohol swab. Be cautious while handling hydrangeas that have fungal infections because the spores can be easily transmitted by hands and cutting implements.
- Apply a leaf fungicide every two weeks from spring through October if the illness is extremely bad. Starting in the next spring is recommended because there is little use in attempting to treat an illness beyond mid-autumn. Fungicides can function as a deterrent on new leaves if applied early enough in the year, but they won’t be able to remove the brown spots from the existing hydrangea leaves.
- Fungal diseases rarely require the destruction of hydrangea plants, but if you’re worried about the illness spreading to surrounding plants, you should think about it.