P&PDL Picture of the Week for
May 2, 2005

Smart planting

Mike Dana, Extension Landscape Horticulture Specialist, Department of Horticulture, Purdue University

Sometimes, the merciful thing to do is put a plant out of its misery.  This crabapple was a very poor choice as a street tree from the beginning, with too little space and a spreading natural tree form which was incompatible with adjacent sidewalk and parking functions.  It might have been pruned into a single-trunk tree very early and perhaps made into a more useful plant in this location, but that opportunity was missed.  Thus, over the years, it has been hacked into submission on all sides.

The question was raised as to whether there was a remedial pruning approach that could make something useful and attractive out of this tree.  The answer is clearly no.

Replacement, with a slender, upright (perhaps even columnar) tree form, pruned high so the lowest limbs will not conflict with traffic (truck, auto or pedestrian) is indicated.

 

Click on image to enlarge


A Galling Situation on Junipers

Karen Rane and Gail Ruhl, Plant Disease Diagnosticians, Purdue University

Cedar-apple rust is a fungal disease that is quite common in the Midwest.  Rust fungi have very complex life cycles, often involving 2 distinct plant hosts. In this case, the cedar-apple rust fungus infects both junipers (the evergreen host) and Malus sp.(apple, crabapple). The orange, jelly-like protrusions on the juniper gall in Figure 1 are called telia, and contain fungal spores which  are splashed to the developing leaves of apple and crabapple and cause yellow-orange leaf spots. Apple fruit can also be infected, resulting in raised, blister-like brown lesions. Spores from infected apple trees are moved to junipers (again, through wind-driven rain or air currents), and infect twigs, resulting in galls.  The juniper galls (Fig 2) survive for several years, producing orange telia each spring.

A publication on these rust diseases, entitled Cedar Apple and Related Rusts, can be found at the following website: http://www.ces.purdue.edu/extmedia/BP/BP-35.html

This disease is a concern to commercial fruit growers, because it can cause blemishes on apples. On the juniper evergreen host, the disease causes little damage and we don't recommend any chemical treatments.

Figure 1 courtesy of Ohio State University

Figure 2 courtesy of Peggy Sellers

Fig. 1

Fig. 2 Cedar apple rust gall on juniper without spore horn

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service