To diversify or not: red cedar & crabapple trees
It’s still the middle of winter, but not very far off, spring will be sneaking around the corner. We will have had enough of the snow and cold. We will be looking forward to the warming air and emergence of different plants and flowers. Now is a good time to think about Spring and planning some conservation practices on your property. Maybe you would like to plant a wind break, a plot for wildlife or a space for a pollinator planting. Depending on the size of land available there are many options to consider. Sometimes it is nice to have a native planting for the value of different beneficial insects. Many times, homeowners will want to establish some ornamental plants and trees to sharpen up the look of their property. Planting conifer trees are always nice as they hold their color year around. They also provide harborage for birds and wildlife.
Diversity in planting trees is a good consideration due to the potential of disease or invasive insects. If all of your planting is of one species and an outbreak occurs, they all could be infected in a few years. Many times, different conifer and deciduous trees are mixed together to have a nice aesthetic appearance. However, there are some species of trees that should not be planted in the same vicinity of each other. One combination of trees that do not belong near each other is the Red Cedar and the Crabapple or Apple.
When these trees are near each other they are susceptible to cedar apple rust. This is a fungal disease that needs both the juniper and apple tree to exist. This is somewhat of a complex disease that requires a two year life-cycle. Spores overwinter as a reddish-brown gall on the twigs of juniper species. In early spring during wet weather, these galls swell, and bright orange masses of spores are blown by the wind. They then infect susceptible apple and crabapple trees. The spores that develop on these apple trees will only infect junipers the following year. From year to year, the disease must pass from junipers to apples to junipers again. It will not and can not spread between apple trees alone.
On crab-apple and apple trees, look for the pale-yellow pinhead sized spots on the upper surface of the leaves shortly after bloom. These gradually enlarge to bright orange yellow spots which make the disease easy to identify. Orange spots may develop on the fruit as well. Heavily infected leaves may drop prematurely. On juniper trees, look for orange fungal fruiting bodies that have a sticky rubbery texture.
For more information:
Cedar-apple rust: A tale of a fungal disease with two hosts