Re: CULT: aspects of rot - long

In the absence of applied research on bacterial soft rot as it relates to 
irises, application of logic is of some benefit.

Most of the tratments/vodoo/antibiotic/physical intervention or other , 
suggested to us encourage the use of substances to kill/retard/prevent 
infections. While all have enjoyed some measure of success, my thus far 
experience is that infected plants are about as adapt at curing themselves as 
my ability to cure them regardless of the treatment method I choose. For me 
cure rates run in the ten to twenty percent range with or without my 
intervention. Still my intervention continues.

One would think since most of the preventative and infestation treatments 
suggested are usually caustically alkaline that irises growing in alkaline 
soils would experience a lower incidence of rot than those growing in acidic 
soils. To a degree this is supported by my experience here. But, only to a 
small degree. I still have rot attacks in modestly alkaline pH beds. Only one 
small bed with a relatively high pH (10.5) has yet to have any rot. This is 
not conclusive because the varieties planted in it have not contracted rot in 
other beds either, suggesting a genetic component to the rot issue.

Irises dug and placed in a dry environment can but rarely do show physical 
manifestations of rot.  In most circumstances they just continue to dry from 
the evaporation of moisture. I dried several hundred apparently healthy 
rhizomes for 2 months. At planting time about 6 of these rhizomes had rot 
(about 1%). This leads me to suspect that (1) Rot may be present in any 
rhizome even when the physical manifestation of its presence is not 
immediately observable and (2) the drying process is of some value in 
identifying rot contaminated rhizomes and the drying process itself may cure 
some.

Several credible sources suggest soft rot is initiated through insect bites 
or other damage to the rhizomes. Arguably, this may be the case. More likely, 
it is just one of the cause and effect relationships that contribute to rot 
susceptibility. Since the bacteria causing soft rot is generally accepted to 
be a soil born organism present in most soils, it would seem more probable 
that attacks can just as easily be initiated from any portion of the plant, 
from root filament to the leaves where the plant becomes weakened beyond it's 
normal damage tolerance range. Recent post concerning increased rot following 
grasshopper invasions during dry periods support this scenario and cause me 
to suspect the nearer the ground the damage occurs the more likely a rot 
incursion will occur in any given rhizome.

Rotting of rhizomes after receipt and prior to planting has occurred for me 
and others. While this is not common, it does happen. For me it has been more 
common to observe a leaf, near the leaf base, show visual indications of soft 
rot. This deterioration occurs on the margin of the leaf edge where it 
closely wraps an adjoining leaf. This may or may not be soft rot. But it has 
on occasion exhibited all the characteristic symptoms including the foul 
odor. I have never allowed the infection to progress to confirm it 
positively.

Some discussions regarding ideal shipping preparation prompted me to begin 
contemplatin' more than just how to make sure plants arrive at a destination 
in good condition. John had suggested hanging them upside down for a day or 
two in order to promote drainage after washing. That seemed a reasonable 
precaution and more.

Taking cross sections of an iris leaf in relatively small increments from the 
top down shows the leaf cells to be tightly compacted and the two sides 
adjoined in about the top 1/3 of the leaf. In the bottom two-thirds of the 
leaf a hollow cavity exists. One obvious reason for the cavity is to increase 
the rigidity of the leaf by increasing the diameter and allow it to be held 
in an upright posture. Too, the volume of the cavity increases or decreases 
as the plant perceives the need to regulate moisture requirements and 
transpiration needs. We observe this easily when we severe the root system 
digging irises and transplant without trimming the foliage. The cavity volume 
decreases, the foliage bends (wilts). Certainly the leaf cavity facilitates 
other essential functions e.g. temperature regulation and other functions 
relegated to plant leaves generally.

When irises foliage is trimmed into the cavity area we are wise to allow the 
ends of the leaves to wither to the point that the leaf is well closed 
together before planting. If an outside leaf does not close the cavity, we 
are wise to remove that leaf. Whether breaching of the cavity is done by the 
gardener's shears or grasshoppers, the effect is the same. Until the 
structural integrity of the leaf is repaired the plant is at risk from a host 
of attackers. Easy entry of insects, wind born bacteria, sores, etc., for 
sure is much easier. Arguably perhaps, the accumulation of excess moisture 
within the cavity from rain, irrigation, and most likely in the grasshopper 
wars incident, condensation. A wounded leaf with an open cavity would appear 
capable of condensing moisture supplied by both the plant and atmosphere, 
holding it, and maintaining conditions favorable for the growth of soft rot 
bacteria. While I do not believe this is the only source for soft rot, I 
strongly suspect it is one source for the villain's entry and propagation.

Due to the grasshopper war posts, I began paying more attention to the 
varmints behavior. They rarely descend to ground level here while foraging. 
Admittedly they have never had to do that here to find something to eat. They 
rarely descend to ground level in thick vegetation whether just watched or 
chased. When moving from plant to plant they alight in the top portion of the 
plants, crawl around, and find a place they can easily penetrate the 
potential food source. When moving among stressed (wilted) iris plants this 
places their attack at the apex of the hollow leaf cavity. When they are 
feeding among irises with upright foliage, their attack causes minimal damage 
because they are attacking only the top 1/3 of the leaf. During this 
observation I noticed they avoided the oregano patch bordering the iris bed 
being observed. When they lit on it they move on quickly. When I chased them 
their they would not stay. I could find no grasshopper damage on the oregano.

This suggests that grasshoppers and oregano are similar in nature to me and 
poke salad. They avoid oregano until there is nothing else to eat as I did 
the poke salad until I began acquiring new iris introductions. <g>

My observations in an iris bed overrun with foxtail grass supports Linda's 
assertions that a degree of iris protection is afforded by beds so infested. 
This particular grass grows thick at the base and protects the arguably 
critical lower 2/3 of the iris leaf. Grasshoppers do not willingly become 
entangled in the thicker portions of this grass             or others. While 
growing green manure crops in an iris bed defies both aesthetic and 
conventional wisdom, it does represent another weapon available in pest, 
moisture, and perhaps rot control under the special circumstances encountered 
in the Texas Grasshopper Wars. I am currently replanting a bed and recording 
the incidence of rot and grass hopper damage among the inhabitants in what is 
expected to be a small indicative but inclusive sample.

 Invariably we find ourselves using the Nathan Bedford Forrest's approach. 
When we are surrounded by the enemy we attack in all directions. In those 
rare circumstances when we do retard or cure rot, we rarely have an 
understanding of the cause/effect involved, if we actually affected a cure or 
if the plant might have effected a cure on its own. While the afore mentioned 
has some merit it does not lead us to a practical solution and probably won't 
until we can perhaps persuade the AIS to commit substantial resources/funds 
and commit them on a non political basis toward applied rot related research 
(Soapbox # 3).

Were the question posed to the AIS membership "Would you prefer the AIS 
retaining $250,000 in cash accounts or would you prefer the AIS spending 
$50,000 on rot cause/control/eradication/cure research and retaining $200,000 
in cash? I suspect the answer would be a given!

Patience grasshopper. Patience!
Bill Burleson 7a/b
Old South Iris Society



  













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