Fight the Fungus: How to Recognize and Treat Fig Rust
Updated: Sep 30
Want to make your garden stand out? Grow a fig tree! With their delicious fruit and beautiful foliage, fig trees are a favorite among gardeners and fruit tree enthusiasts. But, beware! Just like many plants native to dry and warm climates, fig trees can be prone to a fungal infection called rust in areas with high humidity.
Don't let rust ruin your fig tree's beauty and productivity. Learn how to recognize and address this fungus before it causes significant harm. Remember, prevention is always better than reacting when it comes to fungal issues. Keep your fig tree healthy and fruitful, take action now!
Fig trees are a desirable addition to any property due to their tasty fruit and attractive foliage, making them a favorite among many gardeners and fruit tree growers, but when grown in humid climates, fig trees are susceptible to fungal infections, specifically rust, when grown in areas with high humidity.
Rust can be identified by small yellow spots on the upper surface of the leaves, which grow larger over time and turn a reddish-brown color.
Rust typically appears during late summer and in severe cases, it can cause the fig tree to lose its leaves in a matter of weeks, which can have a significant impact on the tree's growth and yields, as well as its overall health.
Preventing rust is the best way to avoid the problem in the first place by using techniques such as proper fig tree pruning, regular cleaning of leaf litter, use of fungicides, and keeping your tree dry and by using special soil nutrients like silica.
Check out my video on fig tree rust for additional information:
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Identifying Fig Rust
The early signs of fig rust are small yellow spots on the upper surface of the leaves. These spots, also known as lesions, will grow larger over time and turn a reddish-brown color, but they tend to remain relatively smooth. On the underside of the leaf, the lesions will have a reddish-brown color and a slightly raised blister-like appearance. When the infection is severe, the leaves will turn yellow or brown, particularly around the edges, and fall off the tree prematurely.
Rust typically appears during late summer and in severe cases, it can cause the fig tree to lose its leaves in a matter of weeks. This can have a significant impact on the tree's growth and yields, as well as its overall health. If defoliation occurs regularly, the tree's growth may be reduced and yields may be affected due to a loss in photosynthesis.
Reach the end of the article for more leaf problems that affect fig trees and what they look like.
Why are My Fig Tree Leaves Turning Rusty?
Fig rust is caused by a fungus called Cerotelium fici, which thrives in warm and moist environments. The fungus infects the fig tree through its leaves, making other leaves on the tree and neighboring fig trees more easily infected with rust if conditions continue to be wet and humid. For example, one droplet of water that carries the fungus can spread fig rust to other leaves and other trees.
Does Fig Rust Go Away?
Fortunately, fig rust can seemingly go away on its own. In dry years, fig rust is not observed in my Philadelphia area climate. While in wet years, growers in the humid mid-Atlantic or Southern United States can see severe infections of fig rust. In these climates, a severe infection occurs almost every growing season.
In dry places like most of California, Arizona, or West Texas, rust is something you'll rarely observe. Even if you received a tree with rust on it, the fungus will not spread and the following year after a period of dormancy reveals no trace of rust whatsoever.
Fig rust is worth worrying about in places where severe infections can occur. You can sleep easy for the rest of us knowing everything will be fine.
Combatting Fig Rust
Preventing fig rust is the best way to avoid the problem in the first place. Proper fig tree pruning, regular cleaning of leaf litter, use of fungicides, and keeping your tree dry are all effective ways to prevent rust from forming. Special soil nutrients like Silica may also help. Examine the leaves daily for any sign of rust, and take action immediately if you spot any rust-infected leaves.
Proper fig tree pruning is a crucial aspect in preventing the infection of rust as it improves the tree's overall health, vitality, and production. Pruning helps promote better air circulation and sunlight penetration, which can help dry out the leaves and make it harder for the fungus to thrive.
Additionally, by removing excess growth that's not producing a large number of carbohydrates through photosynthesis, pruning can also decrease the amount of leaf litter on the ground that can harbor the fungus and prevent it from spreading.
Lastly, proper pruning can also help to shape the tree and maintain its size. With a well-pruned tree, it will be easier to spot any signs of rust and treat them early on.
Cleaning up Leaf Litter
Cleaning up leaf litter around the tree is a simple but the most effective way to prevent the further spread of fig rust. By removing the source of the fungus, it's only logical that you'll see results.
In severe cases of fig rust, the leaves will fall from the tree and they can create a humid microclimate around the base of the tree, which can provide the perfect conditions for the fungus to grow and spread. Additionally, when the leaves are wet, they can provide a source of moisture for the fungus, enabling it to survive and infect the tree.
Use of Fungicides
The use of fungicides can also aid in preventing fig rust, but it is important to follow the manufacturer's instructions carefully. Fungicides are chemicals that are specifically designed to kill or control the growth of fungi and can be an effective tool in controlling fig rust.
Which Fungicides Do I Recommend for Fig Rust?
If I were going to recommend a fungicide (which I don't recommend using), I would always choose the organic option. Copper and Sulfur are both organic and can get the job done. You can also use a dormant oil, which I would recommend using selectively in the winter when growing fruit trees. These are high-quality organic products that I have used below:
When applying fungicides, it's important to pay attention to the timing of the application. It is best to apply fungicides at the first sign of rust before the infection becomes severe. Or if you know that an outbreak of rust is likely to occur, spray preemptively. Applying fungicides at the right time can help prevent rust from spreading and causing extensive damage to the tree.
It's also important to follow the recommended application rate and to repeat applications as directed. Most fungicides will need to be reapplied several times over the growing season to ensure that the fungus is kept under control.
It's important to note that fungicides should be used as a last resort after all other prevention methods have been tried and have failed. Fungicides can be toxic to bees and other beneficial insects, as well as to humans and animals, so it's essential to be cautious when using them and follow all safety precautions. I do not spray my fig trees for any reason.
Removing Infected Leaves
Removing infected leaves is an important step in preventing the spread of fig rust.
If you're in a high fig rust pressure location, it's important to remove infected leaves as soon as you spot them, as the fungus can spread quickly. Look ahead to the forecast for rainy and overly humid conditions.
In addition to removing infected leaves, it's also essential to properly dispose of them. You should avoid leaving the infected leaves near the tree, as the fungus can survive in the leaves and infect the tree again. Instead, you should burn or compost the leaves, bury them, use them in tea, or dispose of them in the trash.
Keeping Your Fig Tree Dry
Keeping your fig tree dry is an essential step in preventing rust, as the fungus that causes it thrives in warm and moist environments. Avoiding overhead watering or providing cover for your fig tree are both effective ways to keep your tree dry and make it harder for the fungus to spread.
Adding Important Nutrients to the Soil Like Silica
Silica is a micronutrient that is essential for the growth and development of plants. It is present in high concentrations in the cell walls of plants, where it provides structural support and helps to strengthen the plant's resistance to pathogens and environmental stressors such as fungal infections.
Some studies have shown that silica can help prevent fig rust by strengthening the plant's cell walls and making it harder for the fungus to penetrate the leaves. In addition, silica has been shown to increase the activity of certain enzymes in the plant that are involved in defense mechanisms against pathogens, which can further help prevent rust from taking hold.
I recommend and use diatomaceous earth, vermiculite, and a product called Dyna-Gro Protekt for their high silica content on my fig trees.
Boron is another essential micronutrient that plays a key role in cell wall formation, which helps to strengthen the plant's defense against pathogens. It is also involved in the transport of sugars and other nutrients throughout the plant, which can improve the overall health of the tree and make it less susceptible to rust.
Additionally, zinc and copper deficiency can weaken the plant's defense mechanisms, potentially making it more susceptible to rust.
Frequently Asked Questions
Q: How long does it take to see improvement from fig rust?
A: This can vary depending on the severity of the rust and the steps taken to combat it. However, with proper care and treatment, you should stop seeing the spread immediately.
Q: Can you eat figs with fig rust?
A: Fig fruits are unaffected by fig rust. If you're seeing something that looks like rust on your figs, it's likely fig mosaic virus, a nutrient deficiency, or fig mites.
Q: Will fig rust spread?
A: If not treated, fig rust can spread to other parts of the tree and even to other nearby fig trees. See the photo below:
Q: Is fig rust the end of your fig tree?
A: Far from it. Rust cannot kill your tree, but it can certainly slow it down significantly. In severe cases of rust, the fig tree will drop its infected leaves. If lots of defoliation occurs, the tree will have less carbohydrate production to perform its normal tasks that come from photosynthesis.
Other Leaf Problems Commonly Mistaken for Fig Rust:
Sunburn is probably the most commonly mistaken for rust. This occurs when fig trees are moved from low light conditions to higher light conditions too quickly and do not have the time to adjust to higher amounts of sunlight. Note the brown, white, and bronze coloration.
The video below is titled: Adjusting Fig Cuttings to the Outdoors to Avoid the Costly Mistake of Sunburn - check it out!
This is Fig Mosaic Virus (FMV). These leaves can be malformed, splotchy, discolored, and downright strange. FMV can be significantly lessened by a technique called rejuvenation pruning. I cover that technique in full in the pruning section here:
This is what sooty mold looks like on a fig leaf. The residue left behind from scale on fig leaves and branches can often turn to sooty mold in humid environments. Remove the scale and fix the problem. I would suggest using a high-quality dormant oil that you can purchase here: