“What are Those Orange Things in My Tree?”

Mary Helen Ferguson
NC Cooperative Extension Agent, Horticulture
TREES NC Board Member
Posted May 6th, 2010 in Lawn & Garden

Have you seen the funky orange balls (galls, actually), in cedar trees recently? These are signs of cedar-apple rust or cedar-hawthorn rust. A third fungus in the same genus, cedar-quince rust, results in orange "goo" on cedar limbs but doesn't produce the distinctive balls with 'horns' or 'tendrils.'

These three diseases are similar in that they spend part of their life on a plant in the Juniperus genus (often Eastern red cedar,Juniperus virginiana) and the other part of their life on a plant in the rose family, such as apple, crabapple, hawthorn, or quince. Without both types of plants, these fungi cannot continue their lifecycles.

Incidentally, have you ever wondered why it’s illegal to grow gooseberries or currants in North Carolina? It’s because they are “alternate hosts” of white pine blister rust. As with these cedar rusts, white pine blister rust must have two types of plants to complete its lifecycle, and either gooseberries or currants (or possibly some other obscure member of their genus) are required, in addition to white pine. Many years ago, it was decided that the wellbeing of the state’s white pine industry was worth banning gooseberry and currant plants.

Now that we’re back from that diversion, I’ll talk a bit about what you can do about these cedar rusts. While orange galls look odd on cedar trees, they aren’t likely to do much harm to them. If the plant is small enough and you care enough, you can look for the galls of cedar-apple or cedar-hawthorn rust during the winter, while they’re still brownish in color—they look sort of like little brains, come to think of it—and cut them, with a bit of the plant, out of the tree. Cedar-quince rust will probably be harder to spot on cedar during the winter, as it is manifested as dark-colored cankers rather than roundish galls. Since the galls or cankers of cedar-hawthorn and cedar-quince, respectively, can survive for more than one year on their cedar host, you could also remove infected limbs while they’re orange and highly visible, so that they won’t be around for the next year. Cedar-apple galls only live for one year, and once they have swollen up and turned orange, they die soon anyway.

While some might care more about the appearance of orange galls or goo in their cedar trees, I think damage to apples, crabapples, and other rose family members warrants greater concern. Once yellow and orange circles show up on the leaves of apple or hawthorn trees in the spring, and crabapples have orange spikes coming out of them, it’s too late to apply a chemical to reduce damage. In future years, you can preventatively apply a product containing myclobutanil, mancozeb, or fenarimol to protect your tree. Eagle® and Immunox® contain myclobutanil and, according to the most recent information that I have, can be used on both apples and ornamental trees in residential landscapes. (Always read pesticide labels to make sure that a product can be used in your particular situation, and follow the directions on them—“the label is the law.”)

As I’ve suggested, the timing of a fungicide application to prevent cedar rusts on apple, crabapple, and hawthorn trees is very important. Protection needs to coincide with the time when galls, in the case of cedar-apple and cedar-hawthorn rust, or cankers, in the case of cedar-quince rust, are releasing spores. Since spores will likely already have been released once you see the bright orange galls or goo, and you may never see the cedar stage, since the cedar or other Juniperus tree may not be on your property, application of the fungicide to apple trees can be based on bloom stage rather than sighting of galls or goo. To protect apple trees, wait until the “tight cluster” stage. “Tight cluster” is when leaves surrounding clusters of flower buds have opened up, so that they give the appearance of forming a star around the still-closed flower buds. Between this time and when petals fall off the flowers, you can integrate one of the products that is effective against cedar apple rust into your spray program.

While removing of cedar trees on your property might help protect your apple trees to some extent, the spores of the fungus may travel for several miles. I doubt that removal of cedar trees in a four to five mile radius, as is suggested for complete eradication of cedar-apple rust from apples, is practical for anyone in Randolph County.

There are apples and ornamental junipers that are resistant to one or more cedar rusts, and this is a factor that can be considered when deciding on a juniper or apple variety. 'Empire' and 'Winesap' are two apples that do well here and are resistant to cedar-apple rust. More information on what varieties are resistant and susceptible can be found here: www.uaex.edu/Other_Areas/publications/PDF/FSA-7538.pdf. If you're looking for a crabapple tree that has resistance to rusts and other diseases, you can check out this site: http://www.ces.ncsu.edu/depts/hort/hil/hil-8613.html. A list of hunipers that are resistant to cedar-apple and cedar-hawthorn rust can be found here: http://ohioline.osu.edu/hyg-fact/3000/pdf/3055.pdf. Of course, if you don't have internet access, you call call us for this information.

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.