I have two two year old apple trees. They have both developed yellow spots on their leaves, although one tree has considerably more spots than the other. Could you tell me what they are and will this effect their ability to bear fruit in the future. As of yet they are to young to have started producing any fruit. Thanks
More than likely your apple trees have developed a very common problem that we see every year on numerous apple trees. Apple Cedar Rust.
Cedar-Apple Rust is a fungal disease w/ a complex life cycle. In order to complete its life cycle, the disease organism needs two different, unrelated hosts: One is the Eastern Red Cedar or Southern Red Cedar. The other is a rosaceous plant; plants in the Rose Family. Rosaceous plants include Apple, Hawthorne, Crabapple.
In the winter to early spring, tan to brownish golf ball sized galls can be seen on the stems of the juniper or cedar host. During moist weather in the spring, the galls produce bright orange, gelatinous “horns”, which produce spores. The gall has an appearance of an orange octopus at this point. Spores are distributed by wind and can travel over two miles to infect a rosaceous host. These spores will not reinfect the juniper. In late spring, distinctive yellow or orange lesions are visible on the upper surface of the leaf. Later, cup-shaped structures will form on the lower surface of the leaf. These structures will produce spores that will infect junipers. Cedar-apple rust can cause leaves to drop prematurely from the rosaceous host. A severe infection could cause death of the tree. Fruit may also be infected, resulting in smaller, deformed, unmarketable apples. Infections on fruit often occur on the calyx end but may occur on the sides or even the stems. Lesions on fruit are shallow and orange to yellow or green with a yellow to orange border.
Where rust diseases are severe enough to require control, remove all cedars, if possible, within 1/2 mile of the orchard. Removal of all cedars will usually provide sufficient control in areas of the mountains in the Southeast where the eastern red cedar is not abundant. This is usually impossible!
Fungicides should be applied from early pre-pink through petal fall for fruit infections and from pre-pink through second cover for leaf infections. Of the cultivars planted in the Southeast, Rome Beauty, Gala, Mutsu (Crispin), Braeburn, Ginger Gold, Cameo and Jonagold are most susceptible to cedar apple rust. Delicious is not susceptible to cedar apple rust but is very susceptible to quince rust.
Fungicides that have been effective- Captan and Mancozeb.
More info can be found at ncsu.edu/cedar-apple-rust http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1036/EPP-7611web2014.pdf
Hope this helps.