Cedar-Apple Rust

Andrea Burns
Ford County Extension Agent

May is here!

There were several days this week that did not act like spring, but we are greatful for the warmer temperatures and more importantly the much needed rain!

The lawn mowers in Dodge City have started up and will be busier now that it has rained. The rain has also brought on strange, jello-like, orange globs on cedar trees.

Do not to panic, it is not an invasion of a terrible disease, at least not for the cedars anyway. Cedar apple rust can be identified on cedar trees by the bright orange tendril covered balls that hang like ornaments on a Christmas tree. These are called cedar-apple galls.

They are also the source of the spores that infect apples and crabapples with rust disease. On apples and crabapples it can be identified as a rust-colored lesion or spot on the leaves.

The disease actually started appearing a month ago but the unusually cold temperatures and lack of moisture stalled its development for a bit.

Although the presence of galls on twigs may be unsightly on the junipers, rust diseases generally do not cause serious damage to junipers. This disease is caused by wet weather.

Nevertheless, susceptible trees may be protected from infection by three to four fungicide applications sprayed at 10-day intervals, beginning in early July. Bordeaux mixture, ferbam, and Bayleton are labeled for use on junipers. Because it takes two years for galls to develop, benefits of these sprays may not be noticed until the second year.

Several cultivars of juniper are available with resistance to cedar-apple rust. A complete listing of these junipers is available from the Ford County Extension office.

Homeowners with cedars can rest assured that their trees will not suffer any long-term effects. As soon as the temperatures warm up, the ugly globs will dry up and will no longer spark concern.

Now those with apples and crabapples need to pay attention. This disease can affect the fruit crops and eventually kill the tree.

Susceptible varieties of apples and crabapples that have not been treated are likely already infected, even though you cannot see the signs yet.

We cannot prevent the infection now, but here are some prevention and protection measures to help you out.

New crabapples are less susceptible to the disease and will not completely defoliate like the older, susceptible varieties. They may show signs of the disease, but it will not be as severe.

Other varieties that completely lose their leaves may leaf again if they were healthy prior to becoming infected. Significant damage to crabapples is very rare.

Fruiting apples are the ones that are most affected. They use more energy to produce the fruit itself and exhibit more signs of stress.

It is important to keep the apple trees well watered this year to minimize the stress they will experience.

Homeowners should also avoid new plantings where apples or flowering crabapples will be planted adjacent to junipers.

Fungicides should be applied to apple or flowering crab in the spring to prevent rust infections.

The first spray should be applied as soon as the gelatinous tendrils are noticed, usually in early April.

Applications should continue every 7- to 10-days as long as the galls remain active (usually until the end of May).

Several chemicals, including Ferbam, triforine (Funginex, labeled for apples only), Immunox, and Bayleton are effective in controlling rust diseases. Immunox is labeled for both apples and flowering crabapples. Be sure to read and follow the label directions and rates of application.

For information on cedar apple rust is available from the Ford County Extension Office’s website at www.ford.ksu.edu.

Have a great weekend!