Hi Steve, I believe the rest of your question got cut off.  Would you mind trying to send it again?

Hmm, that's weird. Thanks for the quick reply, I'll try again.

What treatment options do I have to treat some cedar apple rust?

I have a couple of struggling cedars that had telltale signs of rust during some wet weather this spring. The trees are struggling because they had been overgrown by some vines (eglish ivy, poison ivy, porcelain berry, and virginia creeper). The vines are off now, but the trees are in rough shape. I also have a large mature crabapple that I would like to save and improve the health of that has signs of rust and a fair amount of leaf drop already this year. I'm also planning to plant apple trees in the future and would like to minimize the risk of infecting/harming those.

I'm curious if there is a safe to use fungicide (safe for dogs and wildlife like squirrels, insects. bats, and birds on the property) that could treat either or both the cedar and the apple. I'd prefer to keep the cedars, but If I remove the cedars that are in poor health anyway, I'm sure there are other cedars within a mile or 2 that would reinfect the crabapple. 

If I buy rust resistant varieties of apple trees in the future, I'm assuming resistance is not the same as an absolute immunity and that the fungus could still impact the tree's overall health. Is that a correct assumption? Or would I be able to ignore the cedar apple rust problem if I purchased resistant apple trees?

Thanks for your time,

-Steve

Hello Steve,

Junipers infected with rust are not treated with fungicide, either because they will not work well, or because they are impractical to use. (By the time telltale symptoms of infection are visible, the disease is established. Fungicides can help protect uninfected growth if used preventatively, but cannot cure existing infections.)

Rose-family host plants vulnerable to rust can be preventatively treated with fungicide, but for most plants, it's not recommended for the reasons given below. Fruit-bearing trees that produce a harvest (as opposed to those grown solely for wildlife value) can be protected as part of the over-arching spray regimen that is typically needed to keep multiple pests and diseases from damaging the tree or ruining the fruit. Our Growing Apple and Pear Trees page has more information in the "plant and pest problems" section.

While fungicide use might protect uninfected growth when used starting in early spring, it requires annual treatments, where several sprays may be needed to cover about an 8-10-week period each spring during the time spores from infected junipers are airborne. No fungicide is without risk, and even though those chemicals target fungal spores, they can impact bees and other organisms, especially since spraying would overlap with the tree's flowering in this situation. (Sprays should always pause during flowering, particularly on plants requiring pollination to produce fruit for harvest, but that might leave open a window of time that infection can take place, depending on the weather conditions.) Plant infection spread and severity can be highly dependent on weather conditions, so a heavy rust outbreak one year won't necessarily repeat itself to the same degree the next year, though the proximity of junipers known to be infected does significantly increase the risk of yearly infection for the crabapples and apples. Our native junipers do have great wildlife value, so their removal wouldn't be ideal in that regard, but it might be the most pragmatic choice if they will be creating a challenge for disease management and you want to minimize a reliance on pesticides.

You are correct that disease-resistant cultivars are not immune to the disease in question, just less likely to develop severe disease. Fortunately, this is often sufficient, especially in conjunction with a spray program. The sprays you'd already be using to suppress other infections (fire blight, scab, etc.) will probably cover rust as well, especially since a number of widely-available fungicide ingredients are fairly broad-spectrum.

Miri