I noticed yesterday small yellow spots on several varieties of trees that were planted in the spring. We had a dry spring, so I’m assuming the cedar apple rust was late to appear with the recent rains. These being first leaf trees, should I go ahead and spray now with Immunox (I knows it should have been applied earlier), or should I wait to implement a spray program next year?
Spraying now will not do any good. The life cycle of the fungus is such that you need to spray before the spore lands on the tree.
I would not worry all that much.
This was a weird year for CAR here on LI at least. My two ‘marker’ trees are both Eastern Red cedars; a small one in my yard and a real giant in my neighbor’s yard. My tree showed the orange gall hallmarks back on April 28th. Time to get Immunox on. But then my neighbor’s tree had galls show this last Tuesday. Some mix of coolness/dry and then warm wet? Amount of sunlight? (More shaded tree had galls first). Dunno.
I concur with MES, plan for next year.
It also takes a long time before the spots are noticeable. I just noticed spots here a week ago and I am in a warmer area.
If the CAR isn’t bad you don’t need to spray for it, I let my CAR alone for ten or so years. It looks bad but does not harm the fruit production. Some varieties are really bad, and if the cedars are close you don’t have much option besides spray. Quince rust can be much worse. It ruins the fruits whereas with CAR you can generally thin out the small amount of fruit that get damaged.
I’d consider spray. If we do run into more wet weather CAR sometimes will defoliate trees and it won’t help you in establishing yours- even if it doesn’t get that bad. Spray will not only prevent it from jumping on to newly forming leaves, I believe it will actually dry the fungus up if you use Immunox.
Alan, CAR can’t jump from apple leaf to leaf - the spore must have come from a cedar. Its one reason why leaves formed after now never have CAR spots on them. But it makes sense that the spray could limit the growth of the spores already there.
Scott, I couldn’t believe it when I read your comment but it was the first piece of info on a Cornell fact sheet which was the first thing that came up when I searched. It is the only fruit tree fungus I know of that acts like that.
It still may be useful to dry up the existing spores with the Immunox. I believe I’ve seen symptoms get worse late into summer when defoliation seems to occur as a result of very bad infections.
Hmmm…here I was thinking I had avoided CAR this year, for some reason I was thinking the CAR threat was pretty much over for this season. I’ve already exhausted my three myclo sprays for the season. Maybe I’ll cheat a bit and give Goldrush just one more application before everything starts getting Captan and sulfur.
I learned something in this thread because I too thought CAR spread among leaves and even from apple tree to apple tree. Mine certainly appeared to spread last year, but maybe the infection period was ongoing and just made me think it was spreading.
Hey, me too.
Scott always seems to have his facts straight.
Thanks so much for all the info. I think I will go ahead with a spray to be safe.
I sprayed late this year, but just resprayed after rain with Immunox as I found CAR on three apple trees. Can’t find the cedar!
It’s not just from cedar. Do you have any junipers nearby? My neighbors have them.
Here’s what Cornell says about CAR: Cedar-apple rust is one of several similar fungal diseases which could be broadly classified as Juniper Rosaceous rusts.
Examples of juniper hosts include eastern red cedar, southern red cedar, Rocky Mountain juniper, some prostrate junipers, and Chinese juniper.
Examples of rosaceous hosts are apple, crabapple, hawthorn, quince, serviceberry, and pear.
Hmmmm. How to put this. I have been doing academic research my entire working life, so I tend to support Science as a force for good in the world. Should be some dramatic music there. My area, BTW, is structural chemistry, and I have no particular expertise in agricultural chemistry at all. However, one of the things I have learned over many years doing science is that absolutes are not safe. CAR cannot move from apple tree to apple tree? Ever? Why not? I suspect that if I really read the literature, not the pronouncements meant for public consumption, I would find that the spores which develop on apple leaves are less capable of infecting other apple leaves than those which are released from the host cedar/juniper plants. Maybe much, much less capable. Not incapable. I recently sprayed my peach trees for leaf curl, even though the fungicide I used is not supposed to be effective once the leaf curl had developed. I did so after noting that the tree’s response to leaf curl is to drop the infected leaves and grow new ones. I figured the fungicide might help protect the new leaves. Maybe it did some good. Even my Belle of Georgia trees which really seem susceptible look better than last year. Anyway, yes, read and believe the good research on these topics, just don’t think of it as written in stone.
Thanks Mamuang! I found the juniper! Coming out tomorrow! Whewwwwwwwwwwwwwwwww