Up-the-Creek said:
I was wondering, do you know anything about Cedar Apple Rust? This did an absolute job on my apple trees this last year. I have been told to spray them,..but with what??? Do I need to use a chemical? I hope you can help me,..you seem much more knowledgable than my local yocal hardware/feed store employees.
Thanks!
I've never had a problem with Cedar Apple Rust, so I had to Google the info myself. Here ya go:
RUST DISEASES
Rust diseases and causal fungi include: 1) cedar apple rust, caused by Gymnosporangium juniperi-virginianae; 2) quince rust, caused by G. clavipes; and 3) hawthorn rust, caused by G. globosum. All three fungi spend part of their life cycle on red cedar and are problems only when red cedar is found close to the orchard. The life cycles and control of these diseases are similar.
Cedar-apple rust is the most important rust disease in Ohio and the disease is generally more severe in the southern portion of the state. In Ohio, the rust diseases are generally not a serious problem to apple production; however, if the disease is established on cedar (juniper) within a 2-mile radius of the orchard, serious losses can result.
a)
Cedar-Apple Rust Disease Cycle
The disease cycle is very similar for all three rusts and is very complex. For the purposes of this discussion, cedar-apple rust will be used as an example. Two plants (apple and cedar) and three fungal fruiting structures (telia, aecia and pycnia) are involved. The pathogen requires 2 yr. to complete its life cycle.
The cedar-apple rust and hawthorn rust fungi overwinters in reddish-brown galls or "cedar apples" in the cedar tree. The quince rust fungus overwinters in elongated galls in cedar branches. When galls become wet during spring rains, they extrude gelatinous tendrils or "horns" consisting of microscopic two-celled teliospores, each of which produces four basidiospores. Air currents carry the basidiospores to the apple leaf and fruit where they infect under favorable conditions. Leaves are most susceptible when they are 4 to 8 days old. Apple leaves and fruit can only be infected by the basidiospores of the rust fungus from cedar trees. Thus, when the basidiospores have all been discharged from the spore hornes on cedar trees, the danger from infection on apple is past. There is no secondary cycle or infections on apple. Once the lesions form on leaves or fruit, they will not spread or cause additional infections on apple. Instead, another type of spore (aeciospore) is produced and during July and August, these aeciospores are carried by wind back to the cedar trees where they cause infection and complete the life cycle of the fungus.
Note: The basidiospores that infect apple are produced and released from galls on cedar trees from about the "Pink" stage of apple bud development, until about "First" to "Second" cover. If fungicide is required to control this disease, this period is most critical for timing sprays.
Note: Apple varieties differ greatly in their
susceptibility to rusts. Many
scab resistant cultivars also have good resistance to cedar-apple rust, which is the most common rust disease in Ohio. It is important to realize that the resistance reported to rust in the disease resistant apple varieties is for cedar-apple rust. The varieties may not be resistant to quince rust. Due to the lack of effective fungicides for rust control, if quince rust is a serious problem in the area, organic production may not be feasible unless you can eliminate cedar trees within at least a 1/2 mile radius. The use of disease resistance must be emphasized in the Organic disease control program.
b) Bottom Line For Rust Control.
Use rust resistant varieties and eradicate the alternate host within at least a 1/2 mile radius of the orchard.
Get more cedar-apple rust info -
facts and photos here
