‘Tentacle-shaped structures’ in the trees: The strange world of cedar-apple rust

Is a UFO decorating eastern red cedar trees with gooey orange creatures that might take over the world?

Happily, the answer is no, but you may have noticed these rather shocking and downright weird growths on some of your favorite cedars recently, including those found at Harwich Conservation Trust (HCT) properties. These neon knickknacks have some gall!

As it happens, they actually are galls, produced by cedar-apple rust, a common fungus in the eastern part of the country. And this is prime time for the gall to star as perhaps the wackiest thing you’ll ever see in a tree. This description from the Missouri Department of Conservation sounds kind of like a monster movie:

“Upon maturity, and after a spell of wet springtime weather, orange or golden gelatinous, tentacle-shaped structures emerge from pimple-like depressions of the gall. These produce spores. The horns swell in wet weather to look like inflated sea anemone tentacles. When they dry, they shrivel and shrink to look like rusty, crusty spikes or horns.”

Yikes! The orange outburst is part of the rust’s complex life cycle — a fungus fandango involving two different host plants and four different spores. “It requires two hosts to be present, usually within a mile of each other,” according to the U.S. Forest Service. The two hosts include, “a juniper species, usually eastern red cedar, and an apple, crabapple, hawthorn or quince.”

Spores galore

We turn again to the Missouri Department of Conservation for the crib notes on this perplexing process: “Put most simply, the galls that develop on cedar trees create spores that can only germinate on rose-family trees and shrubs, creating yellowish-orange spots and warty growths on the leaves of those plants. Those rust spots, then, create spores that can only germinate on cedars, causing the knobby galls on cedars and completing the two-year cycle.”

Now that we are slightly unnerved by the mysterious fungal power of nature, it would seem prudent to investigate what harm might be caused by cedar-apple rust. So, we reached out to Craig Schneeberger, Arborist Representative for Bartlett Tree Experts in Orleans.

“Cedar-apple rust is very common out here on the Cape,” wrote Schneeberger in an email. “There is very little/nothing that can chemically be done to prevent it on cedar trees. On smaller, younger trees you can prune the galls off to prevent it from spreading. But that’s an uphill battle. They are not harming the cedars.”

That’s good news, but there’s more to the story. “The harm comes when the galls open this time of the year and spread their spores far and wide,” wrote Schneeberger. “These fungal spores land on apple trees as well as crabapples, hawthorns, quince and pear. These spores then infect both the leaves (primarily) as well as the flowers during bloom time. This then ‘mottles’ the fruit as it’s developing and causes leaf drop.”

From a land conservation perspective, we’re reassured by Craig’s comment that, “They are not harming the cedars.” The galls are part of the natural landscape.  As you mosey down the All Persons Trail at HCT’s Robert F. Smith Cold Brook Preserve, take a gander at the cedars and maybe you’ll spot evidence of the funky fungus that is always among us.

Sour news for apples

Sometimes, fungicides are used on apple and other trees that are located near cedars to reduce the impact of the disease, according to Schneeberger. “Aside from this, proper soil care and general health considerations are important because continued leaf drop and damage from the disease has the ability to take away the photosynthetic capacity of the plant,” he wrote.

In a yard or garden setting, the presence of cedar apple rust isn’t a huge deal. According to the UMass Extension, “in many landscape settings, cedar-apple rust causes little, if any, lasting damage to both junipers and apples/crabapples.” However, they add that “at times, the disease can be serious on infected apples, resulting in premature leaf shedding and reduced fruit yield.”

If you own an apple orchard and rely on the crop for income, however, the disease can be a big problem. According to the University of Kentucky Extension Service, “cedar-apple rust is the most common and economically important rust disease occurring on apple trees in Kentucky. Heavy infections occurring over several consecutive years result in stunting, increased susceptibility to winter injury, and failure to produce fruit.”

Can the rust be busted?

Breaking up the life cycle of the disease is a tall order from the cedar side of things. “Under this option all red cedar or juniper trees within a several mile radii must be removed, thus eliminating the source of spores that could be blown into apple orchards,” according to The Ohio State University’s College of Food, Agricultural, and Environmental Sciences. “This method is no longer recommended, because the strategy cannot work without complete removal of the primary host.”

And, from a conservation and ecosystem management perspective we don’t want to cause wholesale harm to the landscape.

From the apple side of things, especially for those who seek out organic produce, it is worth noting that “fungicide application to manage cedar-apple rust is commonly included in the disease management programs of many apple production systems,” according to Ohio State.

Resistant cultivars can help

If you’re an apple farmer, another angle to reduce the effect of the disease is to plant apple cultivars that have shown resistance to the malady.

According to UMass Extension, these cultivars include Delicious (red), Empire, Keepsake, Liberty, McIntosh, Milton, Niagara, Paula Red, Regent, Spartan, and Viking.

It would be easy to view cedar-apple rust as a villain, out to wreck apples and cause sobbing in orchards. But it’s fair to remember that the rust is native to North America, while cultivated apple trees were introduced by settlers.

Cedar-apple rust became more of a problem in the late 1800s, when apple storage and transportation methods improved, giving rise to large commercial orchards.

So, maybe it’s best to view the rust as surefire proof that the natural world holds intricate gearworks that can be tricky and rewarding to decipher. Although it is hard to cozy up to a fruit-reducer!

Here’s one more tip: if, for some reason that is hard to fathom, you thought the gelatinous orange galls on cedar trees looked tasty, think again. “Cedar-apple rust is not edible,” reports the Missouri Department of Conservation. Have an apple instead!

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