Cedar apple rust is a fungal disease caused by Gymnosporangium juniperi-virginianae, which affects apple and red cedar trees, as well as ornamental junipers. This disease may result in premature defoliation and reduced fruit quality in apple trees, while it can be disfiguring for cedar trees [1]. Although cedar apple rust can weaken trees and lower their resistance to other diseases and pests, it doesn’t directly pose a threat to humans.
However, it’s worth mentioning that individuals who have allergies or sensitivities to mold and fungi might experience allergic reactions when exposed to cedar apple rust spores [2]. It’s important for those individuals to exercise caution and limit their contact with affected trees during the fungal life cycle. In general, cedar apple rust is more of a concern for horticulturists and apple growers; proper management practices can help reduce the spread of the disease and minimize the damage to affected plants [3].
Cedar Apple Rust Overview
Gymnosporangium Juniperi-Virginianae
Cedar-apple rust is caused by the fungus Gymnosporangium juniperi-virginianae. This fungus affects plants from two families: Cupressaceae (eastern red cedar and other junipers) and Rosaceae (apple, hawthorn, serviceberry) 1. The disease may cause damage to the health and vigor of apple trees, and although it is not highly harmful to cedar trees, it can cause cosmetic disfiguration 2.
Life Cycle
The life cycle of cedar-apple rust involves two hosts: apple and red cedars / ornamental junipers 3. The fungus forms galls on juniper trees, which release spores into the wind during wet weather. These spores then infect apple trees, causing leaf spot symptoms and premature leaf defoliation 4. In later stages, the fungus produces spores on the apple tree that can infect junipers, completing its life cycle.
Comparison Table
| Feature | Gymnosporangium Juniperi-Virginianae | Cedar Apple Rust |
|---|---|---|
| Fungal Pathogen | Yes | Yes |
| Host Plants | Junipers and Apples | Junipers and Apples |
| Life Cycle Stages | Two Stages (Juniper and Apple hosts) | Two Stages (Juniper and Apple hosts) |
| Damage on Apple Trees | Leaf spots, premature defoliation | Leaf spots, premature defoliation |
| Damage on Cedar Trees | Cosmetic disfiguration | Cosmetic disfiguration |
- Characteristics of Cedar-apple Rust:
- Caused by a fungus (Gymnosporangium juniperi-virginianae)
- Infects plants from two families (Cupressaceae and Rosaceae)
- Requires two hosts (apples and junipers) to complete its life cycle
- Can cause damage to apple trees and disfiguration on cedar trees
Susceptible Hosts
Apple Trees
Cedar apple rust, caused by the fungal pathogen Gymnosporangium juniperi-virginianae, affects apple trees. The disease infects the leaves and fruit of susceptible cultivars.
- Symptoms: Bright orange to red leaf spots; possible premature defoliation if infection is severe
- Examples of hosts: Apple trees, crabapple trees
Juniper Trees
Juniper plants, such as eastern red cedar, serve as an alternate host for cedar apple rust; the disease requires both apple and juniper hosts to complete its life cycle.
- Symptoms: Galls on branches and treetops; potential disfigurement
- Examples of hosts: Eastern red cedar, other juniper species
| Characteristic | Apple Trees | Juniper Trees |
|---|---|---|
| Host Species | Apple, Crabapple | Eastern Red Cedar, Juniper |
| Infected Parts | Leaves, Fruits | Branches, Treetops |
| Symptoms | Orange-red leaf spots, premature defoliation | Galls, disfigurement |
| Impact | Reduced fruit quality, tree vigor | Generally not harmful, cosmetic damage |
Symptoms and Damage
Effects on Apple Trees
Cedar Apple Rust is caused by the fungal pathogen Gymnosporangium juniperi-virginianae. On apple trees, it can:
- Infect leaves and fruit
- Cause premature defoliation if infection is severe1
Some symptoms include:
- Yellow spots on upper leaf surfaces
- Rust-colored spots on lower leaf surfaces
For example, in comparison to a healthy apple tree, an infected one may have:
| Healthy Apple Tree | Infected Apple Tree |
|---|---|
| Green, vibrant leaves | Yellow, rust-colored spots on leaves |
| No twig dieback | Twig dieback |
Effects on Juniper Trees
On junipers, mainly Eastern red cedar and ornamental cedar (Juniperus spp.):
Galls caused by G. clavipes and G. globosum are smaller than those caused by Gymnosporangium juniperi-virginianae.
In bullet points, the main characteristics of Cedar Apple Rust on Juniper trees are:
- Formation of galls
- Less harmful compared to apple trees.
Management and Control Methods
Cultural Practices
- Plant resistant apple cultivars to reduce the risk of cedar apple rust infection
- Remove nearby eastern red cedar and juniper trees as they are hosts for the disease
- Rake and dispose of fallen apple leaves to minimize overwintering fungi
For example, planting disease-resistant cultivars such as ‘Liberty’ and ‘Freedom’ apples can help reduce the risk of cedar apple rust infection in your orchard.
Chemical Control
- Apply fungicides during apple tree bud break and early fruit development stage to protect against infection
- Use products containing active ingredients like myclobutanil or propiconazole
| Fungicide | Pros | Cons |
|---|---|---|
| Myclobutanil | Effective against cedar apple rust | May require multiple applications |
| Propiconazole | Provides broad-spectrum protection | Can reduce fruit quality if overused |
Remember that cedar apple rust is not harmful to humans, and these control methods aim to protect apple trees and fruit quality.
Impact on Human Health
Cedar apple rust is a disease caused by the fungal pathogen Gymnosporangium juniperi-virginianae, which primarily infects apple, crabapple, eastern red cedar, and other juniper species source. It poses significant risks to the plants it affects, but its impact on human health is minimal.
There are no direct health effects caused by cedar apple rust on humans. The primary concern is its impact on the apple industry, as infected apple trees can suffer defoliation, reduced fruit quality, and tree death in severe cases source.
In conclusion, cedar apple rust is not harmful to human health, but it poses significant threats to the health and vigor of apple trees and related plant species.
Footnotes
6 Comments. Leave new
I’m loving the recent gall posts. To me, galls are one of the most beautiful things in the natural world. They are often outwardly beautiful, but even when they are not, the interaction between an insect and a plant that goes on to bulid such a structure is surely one of the most intimate and beautiful interactions in the world. So thanks from a huge gall fan.
We wish we had time to post more about the relationship between insects and the plants that they form Galls upon, but much of that is already posted in our archives.
I just found pods very similar on my Magnolia tree that I planted 10 years ago. I had never seen anything like it until just this spring. Actually it is on 4 of my magnolias and appears to be killing them! Any idea what I can do to stop it? I have taken pictures of the pods but not sure how to add them to this post.
I am from NJ and it’s July 29th 2015. I just pulled a handful of deformed pos off my 6′ Magnolia just like the one in the photos above. Should I be concerned, the plant looks healthy enough.
R. Pichette
I have the same issue on my magnolia. Despite the fact it might be an insect the only way to know is to open it. Having opened it you would have found red, round seeds of the magnolia tree that it belongs to. Squirrels often take them and open them up in my blue tip spruce so I find the same red seeds relocated in a different area.
If you seriously have spent 50+ years exploring outdoors you would have found that discovery is second to curiosity and the best way to answer your own question would be to dissect what you have found and attempt to give more information.
How do I treat for Creosole Gall. I have several Croesole bushes dying. What can I use to treat the bushes. Please help me. Thanks