Question

Some of my wax myrtles have a rust colored growth on the trunk.  When you touch the growth it disperses like a fine powder.  Some sort of spore thing I guess.  The growth appears to have a fiber growth that the rust colored powder is attached to.  The bark appears cracked in the area where to rust "ball" is attached.  It appears to be killing the wax myrtle.  I have lost a few already.  I first notice some dead leaves then the shrub dies.  Not sure if it is the rust colored "stuff" or under watered, etc.  Any clue?  Located in south Texas

Answer
Hi

Wax myrtles are nearly indestructible, with the exception of windthrow.  The rust colored stuff may be a slime mold which would not be pathogenic to the tree and is just there to reproduce.  I would suspect some other problem such as too much or not enough water.  This will depend on how big the plants are and the soil type, which should be sandy in your location.  You may need to provide more water, especially if the plants are less than 3 years old.  Good Luck.