So yes, a spore than travel 4.5 miles can theoretically infect a susceptible tree, but isn't the response and the severity of the infection concentration dependant? Meaning do more red cedars in close proximity severely increase the dose that the apple trees are exposed to in a linear proportional fashion?
Because saying the neighbors have some and my trees are stunted but alive I would ASSUME (I don't know, I'm asking) is a different story than planting red cedars in the close vicinity of susceptible apple trees. Also, prevailing wind directions I would think would have a significant effect, as in most places apples planted west of cedars wouldn't get as near a high dose as the opposite scenario.
Logically that makes a lot of sense that more cedars equals more galls and thus more spores and more damaged apple trees from cedar rust.. However there is an apple tree here rooted 3 ft. from this cedar tree which has over one hundred very active rust galls on it. Over a hundred rust galls is an extreme amount of rust galls on one cedar tree for this property. This tree regularly is rust gall filled each year.
The apple tree rooted three feet away and actually intertwined in this rust infected cedar tree put up with the high rust gall volume and extremely close proximity just fine. Apparently in the case of this example an extreme amount of cedar spore had minimal effect on the apple tree even though it physically couldn't have been any closer to the infected cedar tree. From this and completely unscientifically as it is I am interpreting that an apple tree either is or isn't overly susceptible and for those that show susceptibility to an unacceptable level of rust damage, there are already enough spores in the air here to seriously infect an apple tree. And for those apple trees that do not show susceptibility an increased amount of spores may not hurt the tree or at least in this case an increased insane amount of spores did not hurt the apple tree next to it. Thus planting more cedar trees may not increase the negative reaction of the apple trees on this property unless those apple trees are the susceptible types. Of course as we all know every property is very different.
Another question jumps out and that is are certain red cedar trees more prone to harboring rust galls? If so then those cedars with lots of rust galls maybe should be destroyed or at least the galls can be pruned out of the cedars and destroyed.
Note the pictured cedar tree is history as it did become winter deer food this year as that apple tree was released this winter.
EDIT--Just thought I would add that there are hundreds and hundreds of red cedar on this property and hundreds more reseed themselves regularly over the years. Most seedlings are eaten but some do make it through each year. Even with this increase in cedars I have not noticed any increase in cedar rust damaged apple trees over the years. Not a detailed study but no increase in damaged noticed.
