Dave,
Thank you for the interesting information.
I have been using glyphosate, typically once or twice per year,
for many years, but I have difficulty building a case that glyphosate
contributed to the damage. In the past several years I have used 1
to 1.25 quarts Roundup Weather Max (48.8 % a.i.) per wetted acre,
plus Choice (a Loveland product containing ammonium sulfate) at rate
of 3 pints per 100 gallons of tank mix. The block containing the
Budagovsky roots and trunks received just one Roundup plus Choice
application in 2008, on September 5, at the one-quart rate of
Roundup, applied in a rather dilute mixture of 50 gallons per wetted
acre. On the same day, I used the same mix on another block of 2
acres. The two-acre block consists of trees mostly 10 years old on
MM 106 rootstock, grafted low to Enterprize, and subsequently topped
with one of 6 commercial fruiting varieties at the 5 foot height,
on limbless trunks. Macoun is not included in that block; but all
600 trees there have remained free of winter injury. About 200 Macoun
trees grafted 12-16 inches high on MM 106 rootstock are included in
two other blocks of 30 year old trees that also get Roundup
treatment, typically twice per year. In 2007 they had Roundup plus
Choice ( 1 quart/Acre; 3pints/100 gallons) in about 40 gallons mix
per wetted acre. Here, of roughtly 1500 trees, including perhaps 100
on M26, I saw only one tree (Empire/MM 106) that had bark cracking
essentially identical to those that were so common in the Bud 54-118
block. The Empire tree had just one crack, and suffers only cosmetic
injury.
I did not mention in my original report that 500 trees of Bud
54-118 growing as a nursery at close spacing, and now about 6 years
from their planting as rooted cuttings, show no bark splitting. All
were given the same Roundup treatment as the injured Bud block, on
the same date last September. I am a bit unsure now about my
original plan to make orchard from these 500.
Southwest winter trunk injury is not terribly uncommon in the
history of my plantings, but the damage to the Macoun/Bud 54-118
trees is rather different in appearance, and far more severe than any
I have seen before. About 8 or 9 years ago, a small number of Macoun/
Bud trees developed a single long bark crack, which did relatively
minor damage. It appeared only on the south-facing side of the
trees. In my current state of uncertainty, I am more inclined to
blame dormant pruning than glyphosate as the non-weather factor
tipping the balance toward winter injury in a rootstock that may not
be suited to the particular use described here.
David
On Feb 4, 2009, at 11:37 AM, Dave Rosenberger wrote:
Hello, Dave --
Have you been using glyphosate in this orchard? If so, the e-mail
exchange that I am pasting in below may offer an alternative
explanation of what is going on? For whatever reasons, my
observations suggest that there is a unique susceptibility of
Macoun trees to what we think is injury caused by glysphosate. The
following info from the ornamentals industry was passed on to me by
Jon Clements and raises interesting issues that need further
investigation;
Hi, Jon --
Thanks for forwarding this article. It sounds like Hannah
Mathers in Ohio has documented in ornamentals what I have
suspected for a long time in apples, especially Macoun trees. I
summarized some of those concerns in an apple-crop post on
3/15/07, but I never had the time/resources to run trials needed
to prove the association between trunk damage
