Susie Bowman has a cedar situation. 

The red cedar trees in the field behind her house are infected, which means that the apple trees in the area also may be in jeopardy. A match made in heaven these plants are not. In fact, they make a toxic twosome if they are in the right (or in this case, wrong) company.

Though they say that it takes two to tango, the apple and cedar tree duo will only take part in a dance of destruction if there is a threesome. The third player in this terrible triumvirate is a fungus called Gymnosporangius juniper-virginianae, or, more commonly, cedar apple rust.

Cedar apple rust is a disease of more than just those two species. In fact, cedar apple rust can affect many varieties of cedar or juniper trees and also infect multiple types of apples and some other closely related species in the rose plant family, such as crabapple, hawthorn, serviceberry, pear andquince. 

The telltale signs of infection are present in the trees in Susie’s backyard. Her cedars have brown kidney-shaped galls on theirtwigs. These grotesque galls have circular depressions, somewhat reminiscent of a small brownbrain. 

The smart money is on the cedars, which are not damaged by the presence of cedar apple rust. The galls can be pruned out of the tree or will fall off naturally as they usually only last for oneseason. Cedars are, in truth, only a host, though a necessary one in the intricate life cycle of the cedar apple rustfungus. 

The cedar galls are simply safe harbor, holding the fungal spores through the winter. When spring comes and the rains fall, these galls open up and sprout orange gelatinous horn-like projections, called telia. Within the telia are teliaspores that will be released and spread by wind.

Wind transports and deposits the spores onto the leaves of apple or other Rosaeceae species. When infected, the leaves of these species have yellow or orange lesions that in turn will produce aecia, which is the counterpart to the cedar’s telia. The aecia will produce their own spores that will also catch wind to infect nearby cedartrees. And the cycle will begin anew.

Unfortunately for the apple tree, cedar apple rust produces more destructive effects to the apple tree than it does to the cedar. Fruit will be malformed, leaves will drop off early, and eventually the tree will succumb to this infection anddie. 

To avoid this consequence, most arborists recommend against planting these two species near each other. Since winds can distribute the spores up to a few miles, one must check the entire neighborhood for cedars before planting an appletree.  Fungicide is another option to control the spread of cedar apple rust, or consider planting rust-resistant fruittrees. Red delicious is one apple variety th at is not affected by the rust, but, in a wicked turn of events, it is also one of the more tasteless apple varieties.

Neither Susie, nor any of her neighbors for that matter, should expect a healthy apple crop anytime soon. But neither should they worry too much about the effects of this disease on their cedartrees. As Henry WardBeecher observed, “It is not work that kills men; it is worry. Worry is rust upon the blade.” Don’t let worry, or cedar apple rust, tarnish your holiday season. 


Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.