Strange Sight in the Trees: Cedar-Apple Rust

Having a backyard and taking care of plants can be a rewarding experience, but it also comes with its fair share of challenges. Sometimes, you may come across strange things that leave you scratching your head. Recently, a Reddit user in Oklahoma stumbled upon a peculiar sight in their trees – a lot of yellow jelly and what they described as a “jelly alien nut”. Intrigued and confused, they turned to the online community for answers.

This mysterious phenomenon turned out to be a type of rust disease called cedar-apple rust. It requires two hosts to complete its life cycle, with apples and crabapples being the most commonly affected. While the name suggests that cedars are involved, it can actually appear on juniper trees as well.

Identifying Cedar-Apple Rust

The symptoms of cedar-apple rust vary depending on the type of tree it affects. On juniper trees, you’ll notice brown, perennial galls forming on the twigs. As the weather becomes rainy in spring, these galls produce orange gelatinous horns. While the twig beyond the gall may die, there is no significant damage to the juniper host.

On apple or crabapple trees, circular yellow lesions appear on the leaves shortly after they bloom. As summer progresses, these lesions develop into brownish clusters of threads or cylindrical tubes. You can find them under the spots on the leaves, twigs, or fruits.

Juniper tree with cedar-apple rust

Understanding the Life Cycle

Now, you might be wondering how long this disease lasts. Well, galls start to appear seven months after the initial infection. After 18 months, they transform into gelatinous masses. In the following spring, golf-ball-like depressions form on the galls, giving rise to telial horns. When it rains in spring, the brownish telial horns elongate and turn a bright orange color. Once they release their spores, the horns collapse, dry up, and eventually fall off. While the galls die, they remain attached to the tree for at least another year. The infection is most noticeable in spring when the galls are covered in gelatinous masses.

Managing Cedar-Apple Rust

Fortunately, managing this infection is relatively straightforward. You can prune off the infected areas to prevent further spread. However, it’s worth noting that cedar-apple rust won’t kill your trees; it only causes cosmetic damage to the plants. If you prefer a preventative approach, you can use fungicides or choose apple varieties that are resistant to this disease.


In conclusion, cedar-apple rust may be an unusual sight in your backyard, but it doesn’t pose a significant threat to your trees. It’s important to be aware of this infection so that you know how to handle it should it appear. Share this information with others so they can also recognize and understand cedar-apple rust. Happy gardening!