Question: I planted
four apple trees last fall in Katy, Texas. Two of the trees
died recently, one looks like it is on its way out and the
other is still hanging in there. The growth has been pretty
minimal, I've gotten maybe 3 inches of limb growth on all
the apple trees. I pulled up the two dead trees yesterday
to examine the roots. I looked up the symptoms of Cotton
Root Rot, but can't say that what I am seeing on these trees
is consistent. One of the trees has some sort of green fungus
growing on it, similar to what I've seen on decaying Iris
rhizomes and the root growth doesn't look stellar. The other
tree did not have any visible fungus on it and had a decent
root system. All these trees are on M111 rootstock.
All my apple trees have defoliated at
least once this year, I water them once a week if there
is no rain. I grow a few apple trees on a different rootstock
(dwarf) in Houston with no problem. I've given these trees
a lot of attention, mulching, regular watering, etc. because
they are in an open area; no other trees around and are
subject to extreme heat and the occasional strong wind.
I followed the planting instructions from the Extension
web site. The soil where they were planted is sandy for
about 1 ft deep with our typical clay under that. The area
is high, does not sit in water. I had the soil tested before
I planted the trees and the pH was 7.1 (if memory serves
I was hoping you could consider this
case and let me know what you think the problem is.
Answer: Cotton root rot rarely kills within
12 months--it's usually the 2nd or 3rd yr. Symptoms don't
appear to be Cotton Root Rot.
All trees defoliated one or more times in 2004? What was
temporally associated with that? Grasshoppers eating leaves?
Drought stress? A time of numerous days of heavy rain? The
poor growth suggests a site or management problem. The white
crystalline material on the specimens near the soil line
was unusual. Have you been applying fertilizer frequently?
If so, this could be salts accumulating? That seems unlikely
in a high rainfall area. Also, there appears to be some
type of dark canker-like area in wood at the base of the
trunk. This looks like a stress canker, perhaps tissue died
in this area at the same time leaves dropped off. Some people
apply a white-wash or white latex paint to the trunk to
reflect heat in mid-day. The blue-green fungus is probably
Trichoderma or Penicillium fungus, which would be secondary
invaders of plant tissue killed by something else, during
times of high soil moisture. In your case, it looks like
stress, then drowning by irrigation when you attempted to
revive the trees. Perhaps we should call the local plant
police for suspected plant abuse!
One foot of sandy soil over sticky gumbo clay is not ideal
for apple. You should probably stick with some ornamental
that tolerates your soils. If you insist, you might try
again building up a 2 to 3 ft berm 3 to 4 ft. wide at the
top using sandy well drained soil amended with organic matter.
Mulch the berm, but do not pile mulch up against the trunk.
Irrigate often in hot dry weather.
Mark Black, Plant Pathologist