It is doubtful that the
"worm" was an Iris Borer, this time. The Iris borer,
Macromoctua onusta, is native to North America, and it probably fed on
native species such as Iris versicolor before the arrival of Europeans,
who brought bearded irises with them to this country. Originally
thought to be limited to the eastern part of the United States and
adjacent Canada, iris borers have been reported from as far south as
Carolina and as far west as Iowa, Wisconsin, and Missouri; there have
even been a few isolated reports from Texas, Nebraska, and the Pacific
Coast.
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Iris borers are serious
pests that damage iris directly and also create entry points
for bacterial soft rot disease.
The photo to the left
shows the damage caused by Iris borers. Note the left
margins are chewed. Irregular tunnels appear near leaf
bases, and pinholes dot foliage a few inches above the ground.
Leaves may have dark streaks and be wilted or rotten.
Plants may collapse.
Iris borers are caterpillars, the
larvae of a medium sized, nondescript brownish moth. The
moth lay eggs on old iris leaves and debris near the iris
plants in the autumn.
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The eggs survive the winter and
hatch with the onset of warm weather in spring, when the foliage is 5 to
6 inches high.
These tiny caterpillars begin
attacking fresh iris leaves. Early damage is not noticeable.
But as these tiny caterpillars grow, the damage becomes quite visible as
shown in the photo. The leaves of the iris plant can be easily
pulled away from the fan. Full grown borers are up to 2 inches
long, pinkish in appearance, and with dark brown heads.
In the later summer, the caterpillar
leave the iris rhizomes and enter the soil near the plant
where they then become pupae. A pupa is a mummy-like
dormant stage that allows the caterpillar to transform into a
moth. The pupae are about one inch long, dark brown, and
somewhat spindle-shaped and may be seen in the soil during
planting time. In the autumn, they emerge as moths,
mate, and lay the eggs that cause next year's infestation.
The photo on the right shows the moth stage of the iris borer.
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Signs of Borer
infection: small pinholes in the iris
leaves, notched leaves during early summer, small piles resembling
sawdust around the base of the iris plant, and hollowed out rhizomes.
Click the
"worm" above NOW!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Murphy's Oil Soap and Iris
Borers
Taken from AIS Region 18 Bulletin -- Spring 2000
Michael Gullo
West Walworth, New York
(This article was
recently on Iris-Talk and originally printed in the January 1998 AIS
bulletin)
I first heard about the Murphy's
Oil Soap method of borer control in the January 1998 AIS Bulletin.
The title of this article was "Sand and Soap" written by Marie
Gebert. In the article she presented the following advice:
"use a mixture of one half cup of Murphy's Oil Soap to one gallon
of water. Spray on the iris leaves weekly (or after a rain) from
early May to late July. This should be used after any other
sprays."
I use the soap that comes in the
refill bottles not that which comes in the spray bottles which
is already diluted. I feel that a thorough garden
cleanup (very later fall or very early spring) is also very
important to make borer control even more effective. I
have been using this method of borer control for the past two
seasons with great success.
I only find a very small number of
borers that manage to survive the spraying, which I promptly
squish. One could probably combine the oil soap
treatment and beneficial nematodes (alternate sprayings) and
achieve even more complete protection. With just two
sprayings last season I only found a dozen or so borers.
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Marie, in her article, mentions
that she and others in her area (northeastern Connecticut) have been
using it to great effort for five seasons (as of 1998). I don't
believe in using harsh chemical treatments to control pests or other
problems, so Murphy's Oil Soap has been quite a help. Your climate
will dictate how early you need to start spraying. Some years the
first of May is early enough, but lately here I have needed to start
even earlier, usually mid to late April. If you wait till the
borers hatch then it will be too late, at least to stop the early ones.
I won't use harsh chemicals, but
for those who do I would suggest trying a test plot for the Murphy's to
see if it is as effective as chemical treatments. I know of a
number of people who use chemicals like Cygon only out of desperation.
Return
to Top
Diseases
will fall into the broad categories of:
Pest
listings often include:
-
Iris Borer (Macronoctua
onusta)
-
Iris Weevil or
Iris Snout Beetle (Momonychus vulpeculus)
-
Scale
-
Thrips (Bregmatothrips
iridis)
-
Verbena Bud Moth (Endothenia
hebesana)
-
Whiteflies
(Aleyrodes spiraedides)
-
Leaf Miners
-
Other
Other
listings might include:
Irises suffer less from
diseases and pests than most other garden plants under normal
conditions. However, some diseases and pests do attack iris and
they must either be prevented or destroyed to have a healthy garden.
It is much easier to maintain a clean garden than a messy one since many
pests and diseases hide in garden debris and over winter there.
An iris garden should
not be overwatered, overcrowded, or
overfed if it is to be healthy. In warmer climates overhead
watering spreads diseases, overcrowding keeps the air from circulating
and overfeeding makes large, but soft, rhizomes.
Only the most often
encountered Iris diseases and pests are included here. The Iris
Borer is perhaps the #1 problem. Infestation by this pest may
cause other diseases, or other diseases may begin without the borer
being present at all. There may also be secondary diseases to
consider.
Leaf Spot –
Bacterial and Fungal
Leaf spotting may be caused by a
bacterium or a fungus. Both produce rather similar symptoms,
but with practice they can be told apart. The prevalence of
leaf spotting was probably behind the old custom of cutting
down the foliage of bearded irises after the blooming season.
This practice may actually have been helpful, at least with
bacterial leaf spot.
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Fungal Leaf Spot: Fungal
Leaf Spot is common. As many as eight different leaf-spot fungi attack
different sorts of irises, but the symptoms are all the same. Small
spots appear anywhere on a leaf (but more usually toward the tips) and
grow to about ¼ inch in diameter, with a yellowish center and a
distinct brown border. The spots do not get soft and run together as in
bacterial leaf spot, but they can become so abundant that the whole leaf
is destroyed. Heavily infected plants are seriously weakened and will
fail to thrive. Like bacterial leaf spot, fungal leaf spot occurs most
often during wet weather.
In areas with dry summers, fungal leaf spot
comes on with the autumn rains. Fortunately, systemic fungicides work
quickly to limit the spread of the disease. For the sake of appearances,
badly spotted leaves can be removed. Even more so than with other
diseases, fungal leaf spot can be prevented by avoiding crowding (the
disease spreads from plant to plant) and by cleaning up dead foliage
thoroughly in the fall and burning it. Some authorities say that if you
can keep this disease out for two years, it will not recur unless
brought in on new plants. Some gardeners recommend soaking rhizomes in a
solution containing benomyl before planting as a preventative or sprayed
with this solution if the disease is found on the leaves.
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In
Year 2000, Scorch was a major problem in many gardens.
In Year 2001, there was more Leaf Spot in areas of Central and
SW Kansas. |
Bacterial Leaf Spot: begins
at the margins or tips of the leaves and produces soft, watery areas
that spread rapidly and run together, working downward through the leaf.
Eventually the whole leaf may die. This form of leaf spot is relatively
uncommon and occurs during long spells of wet weather. It is found
mostly in northeastern North America.
The only cure is to cut off any infected
leaves well below the spotted region, using tools that are dipped in a
bleach solution between cuts to sterilize them. Always put cut leaves
into a container to prevent walking on the infected leaves and spreading
the disease in this manner. Also, don’t allow irises to become so
crowded that air cannot easily circulate amongst them.
Since the spores that cause leaf spot can live
over winter on garden debris, it is important to keep a clean garden. Be
sure to remove old dead Iris leaves. Keep an eye out for the onset of
leaf spot during wet weather – starting as small yellow and brown
spots appearing near the tops of the leaves first. The spread of the
disease slows or stops when the weather dries off.
Starting in the spring when conditions for
leaf spot are favorable, some gardeners recommend a regular spraying
program. Start spraying about six weeks before bloom. Spray again if
rain should wash it off. Fungicides such as Captan, Fore, Bravo, Daconil,
Kocide and Bayleton are all effective in the control of leaf spot. Using
two of these fungicides alternately is better than using one of them
exclusively, since resistance to a given fungicide can build up with
repeated use. The availability of any particular chemical depends on
state and federal regulations. Consult your local Extension Agent for
possible sources of these chemicals.
How to Deal with Soft
Rot
Jim Loveland
(Copied from AIS Region 18 Bulletin – Fall 2000)
I have been asked many times how to deal with
soft rot. That’s a good question with a difficult answer. Once I
notice soft rot that has invaded my iris patch, I immediately check each
plant to see if old bloomstalk rhizomes are rotting or if it’s a new
rhizome. If it’s in the old bloomstalk rhizome I will cut out, then
pull all the dirt away from around the rhizome and the area I cut.
At this point I sprinkle Comet on the affected
area. Comet is a drying/bleaching agent. I also cut the leaves down to
8-10 inches to allow air and the sun into the area that has been
infected. I cut the leaves on plants surrounding the affected iris too.
I have even gone as far as to remove tree branches so the infected area
gets more sunlight.
Over the last few years I’ve learned that
the sun will cure a lot of diseases infecting plants, and iris diseases
are no exception. In smaller gardens of 30-50 iris, you might consider
planting them further apart than on to one and a half feet. This will
allow for better air circulation. Now if the infected area is very
extensive, I may decide to dig all infected plants, cut out all the rot,
let them lay out in the hot sun for a time. Usually two to four hours is
sufficient time for the rhizomes to dry.
You can dip rhizomes in a ten-percent bleach
solution to disinfect the rhizomes, then immediately rinse well. You can
use a spoon to scoop the rot out, then sprinkle Comet on the infected
area. Use whatever method works best for you. In smaller gardens I would
most likely dig out the infected area for this, in my opinion, is the
best cure method. In my case I grow hundreds, do I use other methods as
explained above.
A friend from worked asked if I
would teach her how to take care of her iris by thinning and
transplanting them. Although these were
"orphan" iris, they were prized by the her because
they originally were grown by her grandmother. We
grabbed up our shovels and headed to her back yard. With
the first lifting, we noticed the pungent odor associated with
bacterial soft rot. I suggested the treatments listed in
this article. Other photos from the infected clump are below.
Much of the foliage had a few brown leafs.
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Soft Rot is a very smelly, soft, mushy
bacterial – Erwinia carotovora -- rot which affects the rhizome
and the base of the fan. It causes the fan to tip over and can usually
be detected by the foul smell. The bacteria which causes this is present
in most soils and enters the iris through an injury such as snail,
earwig, or borer damage, injury from careless cultivation and other
openings. Soft rot occurs most often in warm moist conditions.
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All six (6) of these
photos illustrate the damage caused by Bacterial Soft Rot.
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Overwatering and over fertilizing are
potential causes of this foul-smelling problem. It often appears first
at the base of the leaves where they join the rhizome, and is manifested
by a yellowing of the fans. Keep a sharp eye out for such signs during
wet weather. The sooner the problem is detected the more successful your
treatment will be. The soft mushy tissue must be removed.
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There are a number of ways to deal
with rot. All are most effective if you detest the signs early
and scrape away the mushy parts. Then you can: 1) Drench with
bleach; 2) Dust with granular cleanser like Comet; 3) Dust
with garden sulfur; 4) Drench with aspirin solution; 4) Resort
to Chemicals.
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When this disease is present, the rhizome
should be dug, the infected tissue scraped away with spoons or melon
scoops, and the rhizome allowed to dry in the sun and replanted in
another location. The rhizome may be soaked in a 8-1 or 10-1 solution of
household bleach before replanting. It is absolutely essential to rinse
the bleach solution off the rhizome after soaking. If the rhizome cannot
be dug, clear away the soil, scrape out the infected tissue, and allow
the rhizome to dry for several days before covering with soil. There may
be loss of the mother rhizome but a good chance of saving the increase.
Disinfect all tools after usage too.
Some gardeners dust with a household cleanser
that contains chlorine-based bleach. This works three ways: it helps to
dry the wound, the bleach is fatal to bacteria, and the cleanser
produces a strong alkaline environment in which any surviving bacteria
cannot grow.
Dipping Siberians in Clorox solution is not a
good choice. Better to go with Agramycin (a Streptomycin) or Benlate
works. Also soil sulfur is a slow acting soil acidifier, it would see
appropriate for use with Siberians.
Remember – keep watch to spot softness at
the base of the leaf fan and toppling fans that have separated from the
rhizome. Bacterial soft rot can destroy an entire clump in a few days.
Bacterial soft rot can be prevented by
avoiding poorly drained sites and mulches and by replanting before
serious crowding takes place. Do not add too much nitrogen, which can
produce soft growth, inviting Erwinia bacteria to grow and
multiply. Remember, the disease thrives in wet weather and is most
problematic in the spring and late fall.
Return to Top
There was a lot of iris damage in the Spring,
2000, from Dallas on northward through Kansas and Missouri. The
diagnosis was varied from Scorch, to Crown Rot, to Bacterial Soft Rot,
or just a reaction to "freeze/thaw" damage. All descriptive
damage was similar – brown leaves, leaves not easily pulled away from
the clump, and no noticeable foul smell. There was much discussion
everywhere.
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These three
photographs were taken of Iris Plants in Dallas, Texas in
2000. Diagnosis = Scorch
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The following is quoted from iris-talk on May
4, 2000, from Dana Brown in Lubbock, Texas:
"I also have some scorch. Although I have
had one or two cases of this before on any given year it has never been
like this. I am compiling a list of cultivars to send to Cindy Rivera at
her request. I too have looked for a common denominator and I think it
might be tied to early spring growth and a light freeze. I theorized
that maybe the varieties that were damaged are more susceptible to
freeze damage thus weakening the plant and allowing scorch to attack.
"I spoke with several people about this
during the national and everyone seems to have their own horror story.
It also seems to be the year for scorch. An awful lot of people seem to
be having a problem with it. I wonder how many of them had little to no
winter as compared to normal. That is the only thing that makes this
year different for me. Maybe the lack of winter allowed varieties that
are cold sensitive to start their growth early and then when we had a
little freeze it zapped them. Now, for the hole in that theory, 2 pieces
of the same cultivar, 18" apart, one scorched and the other is
growing and blooming its fool head off.
"One other observation, the scorch is
MUCH worse in the beds I dug last year. In the 2 year and 3 year old
beds there is little to no damage with 80% coming from the 3 beds that
were planted new last year? Too much fertilizer, compost, tender loving
care???? Next question is, will the victims love or should I just dig
them up and throw them away? Some of them were 1999 introductions and
some of them were historics. I don’t want to lose them all either way.
I notice some of them have little bits of green growth (new?) under all
that damage. Should I cut off all of the damaged foliage? Comments,
suggestions??
Scorch is an iris disease of
unknown cause, and luckily it is of rather rare occurrence. Discussions
about the reasons for scorch are contradictory and confusing. Scorch has
unique symptoms. Leaves at the center of the fan begin to die at the
tips, but cannot be pulled free of the rhizome. Scorch begins with
withering of the central leaves and within a few days the leaves turn a
characteristic rusty red-brown, beginning at the tip and spreading down
toward the base. Soon all the leaves are affected. When the affected
plant is dug up, the roots (not the rhizome!) are dead and hollow.
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Some cases of scorch can be treated
by digging up the rhizome and letting it cure in the sun on
asphalt paving for a week or so. This is called the "Hot
Asphalt Treatment." Whatever the scorch organism is, heat
seems to destroy it.
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Scorch is not very contagious, and if it
spreads at all, the agents are likely to be aphids. Control of these
insects can limit the disease. Scorch does not appear to be particularly
contagious since it will occur only in scattered spots of large
plantings.
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These two photographs were taken in
Garden City and Manhattan, Kansas. Diagnosis
Unknown, perhaps Scorch. Note the characteristic brown
leave tips. Note also the apparent healthy neighboring
iris clumps. This random damage is typical of Scorch.
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The article below appeared in Tall
Talk, September 2000, p 28.
Scorch Identified
By John Burton, Hamilton, Massachusetts
For at least the last forty
years, the iris disease called "scorch" has been identified as
a specific ailment with fairly well defined symptoms, but with no known
cause. It has been referred to as a disease of unknown origin. At the
AIS Convention in Omaha this year, there was a research report
presented, and the Region 21 Bulletin described the identification of
the organism responsible for the scorch symptoms.
Scorch is characterized by the dieback from
the tip of the center leaves of the fan and the dieback of roots beneath
the rhizome, but the rhizome remains relatively normal in appearance.
The outer leaves may die back in drought without being scorched, and the
center leaves of the fan may die back first as a result of either borer
or rhizome rot, again without being scorched. In the latter case, borer
presence in the fan or rhizome or rhizome rot is usually readily
visible.
A research team from the Botany Department of
the University of Iowa suspected that the symptoms might be explained by
the malfunction of the conducting tissue of the central part of the
plant and, using electron microscopy, began examining this tissue in
scorched and healthy plants. They did find that the diseased plants had
phloem vessels (those that carry food) blocked by material of a kind
produced by cells under stress. Further study showed that they also
contained particles of an organism of a type called a mycoplasma-like
organism (MLO). These organisms, which are somewhat like a bacterium
without a cell wall, were only found in the phloem of plants with scorch
symptoms. This type of organism is found in some other plant diseases,
and generally can’t be grown outside of living plant cells or
transmitting insect tissue. So far, the team has not been able to track
the insect vector or compare this MLO with other known MLOs.
The fact that MLOs cause scorch suggests that
both antibiotics and heat can be used to cure scorched still under
study, but heat is a safe and easy way to solve the problem. The
research team found that subjecting the scorched rhizomes to a
temperature of 104 degrees F, for three to four days completely cured
the treated rhizomes. Re-sprouted plants showed no symptoms and showed
no MLOs under the microscope. This temperature and time can easily be
obtained in an incubator or a food dehydrator. In fact, growing
untreated scorched plants in un-air-conditioned green houses caused some
of them to be cured by the heat, thereby making it harder to prove that
the treatment was effective. A closed greenhouse or cold frame would
probably work in a sunny week. Fortunately, the heat did not kill the
irises, only the MLOs.
With the cause identified, it should now be
possible to track the insect or insects that spread scorch, and perhaps
find plants which serve as a source of infection to the insect. It also
has been confirmed that scorch cannot be transmitted by soil, water, or
direct contact between plants.
From IRID-ISM, publication of
the Iris Society of Massachusetts, Volume 10, Number 2, Fall, 1990.
The following is taken from the
AIS Bulletin #292, January, 1994, pp 36-39.
SCORCH REVISITED AND A NEW
THEORY
Raymond Smith (Indiana)
For the past 43 years I have been growing TB
irises and hybridizing for rebloom. Over this period there has been
scorch ranging from 1 to 2 percent in both named sorts and seedlings.
Ordinarily all sick plants were culled, but if special, and retained,
they recovered fully in from one to three years.
The purposes of this article are (a.) to
review the research articles on scorch that have appeared in AIS
publications over the last forty years, (b.) list observations
concerning possible causal conditions, and (c.) to suggest a theory that
might serve as a working hypothesis for further research.
In April, 1954, guy Rogers of Texas wrote a
classic description of scorch, "It is first manifest by the tips of
leaves becoming brown. Gradually the brownness continues downward until
most, if not all of the greenness of the fan is gone. The roots are
withered or have entirely lost their vitality depending upon the extent
of the drying up process … The rhizomes will be perfectly firm and
will yield no visible symptoms of bacteria or fungi." (A.I.S. Bulletin
133, 38)
In an article on diseases of rhizomatous iris
in California, J. G. Bald et. al. reported that plant pathologists had
examined diseased irises submitted by Guy Rogers and had found nematodes
of a kind different from those causing root-knot. "Scorched plants
consistently contained the fungus Fusarium; some contained a
watermold, probably a species of Pythium. (A.I.S. Bulletin 144,
79)
The accumulated knowledge concerning scorch
was summarized in 1959 in Garden Irises by A. W. Dimock, a
professor of plant pathology at Cornell University. In addition to many
fungi such as Fusarium and Pythium he also found Rhizoctonia
from roots of "scorched" plants, but he said that none of
these organisms were isolated consistently or exclusively. Furthermore,
he was unable to reproduce the disease by inoculating healthy plants
with any fungus. He concluded his statement with the sentence, "
… we know of no treatment that will eliminate or prevent scorch."
(Garden Irises, L. F. Randolph, 1958, 96)
A further note on Scorch was reported by the
AIS Scientific Committee in 1962. Dr. Bald had found in examining
discolored areas on the rhizomes of scorched plants from California and
Texas that all contained a similar organism which appeared to be a Pseudomonas.
He said that this suggests a possible relationship between the organism
and the disease. (A.I.S. Bulletin 164, 92)
In 1969 Dr. Bald conducted a series of
experiments on lilies and irises and reported that the bacterium Pseudomonas
is "the cause of scorch disease of rhizomatus iris …" He
concluded that the disease usually attacks "when blooms are
developing and expanding … It can destroy the root system in a short
time." (A.I.S. Bulletin 195, 26)
However, an article by Julius Wadekamper in
1972 questions the Pseudomas conclusions. He first adds to the
definition of scorch symptoms by noting that, "The roots of a plant
that shows new symptoms of scorch in the leaves are already
shriveled."
Wadekamper found at least four types of fungus
in the diseased roots, but concluded that the fungi "were secondary
and were present as a result of the deteriorating tissue and not a cause
of the initial deterioration." He further found it impossible to
transmit scorch to irises by bacterial inoculation and therefore
concluded that a pseudomonas cause of scorch has not been proven
and is in serious question. (A.I.S. Bulletin 204, 21)
[Injection included from Wadekamper article
printed in A.I.S. Bulletin 204, 21, "Mr. James Seeden
of Minneapolis noted eggs of an insect on scorched plants that he did
not find on healthy plants. These were identified to be Diptera of the
family Mycetophilidae and were present on scorched plants as a
result of the condition of the plants and not as a cause." What if
these finds are not totally substantiated? What if the massive swarms of
flying ants which invaded my garden in 1999 carried the cause of Scorch
Disease? The fall of 1999 has been the only year of encountering these
insects, and spring of 2000 has been my first year to encounter scorch.
Is this coincidence too simple?]
Six months later Wadekamper published the
results of three experiments related to scorch. The first indicated
that, contrary to some suggestions, ozone did not produce scorch in
irises.
In the second study, seven different plants
were treated with diseased iris plant sap from roots, rhizomes and
leaves. A leaf from each treated iris was mascerated and then one half
of each leaf was then rubbed with the diseased plant sap, the other half
with distilled water. No differences were found between the halves of
the experimental plants for any of the seven.
In the third experiment, root and rhizome sap
from both healthy and diseased plants were compared by electron
microscope to search for difference in virus particles. Again no
significant differences were found. These three negative findings
suggest that either the variables, that is ozone, sap from diseased
plants and virus particles are all benign when applied to healthy
plants, or that the experimental designs were incapable of producing
detectable differences. (A.I.S. Bulletin 206, 63)
In 1978 publication of The World of Irises
included a fine summary chapter of iris diseases written by John Weiler.
He summarized knowledge of scorch to that year and added that although
reports of the incidence of scorch is greatest in the tier of southern
states, neither the cause nor the control of the condition is known. (The
World of Irises, Bee Warburton, 1978, 346-7)
The next mention of scorch in the Bulletin
was an article by Paul Black in which he reported a devastating
incidence (up to 70%) in his own plantings. He noted the universality of
the disease throughout the United States with the exceptions of
Washington, Oregon, Utah and Idaho. Also it has been found throughout
bearded iris classifications, as well as in the non-bearded Louisianas.
In his own gardens most scorch appeared during times of rapid growth,
and that it seems to occur most often in clean, well kept gardens which
suggested to him that it might enter the plant through a damaged root
system due to cultivating or weed pulling. As treatment, Paul began
incorporating the fungicide Terrachlor Super-X into the soil and
practically eliminated the disease. He found that the use of Terrachlor
liquid drench worked equally well. He began regular use of Terrachlor
Super-X at 9 lbs. per acre but cautions that this is three times the
normal dosage and may not be proper. Also a fungicide at this dosage
could be affecting any fungi or bacteria present. His treatment worked,
but possible efforts on plants or soil were undetermined. (A.I.S. Bulletin
252, 32)
Conditions Conducive to Scorch
I have noted the following conditions
accompanying cases of scorch in my garden.
- Root Damage: rototilling, hoeing
- Leaf Damage: virus, fungi, bacteria, and
rabbits, tramping from animals.
- Rhizome Damage: borer, crown rot, soft
rot
- Competition: closely grown seedlings
- Herbicides: soil chemical build-up
- Insecticides: e.g. Cygon a bit strong can
initiate leaf desiccation
- Soil pH: either excess acidity or
alkalinity
- Lack of trace minerals: weak plants
- Lack of humus: weak plants
- Lack of Nitrogen, Potassium, Phosphorus,
Lime: poor growth
- Roots of trees or other ornamentals
- Major changes in climate
- Any combination of the above
- Weather conditions:
dry - augments tilling danger
hot - augments crown rot
wet - compacts soil, eliminates oxygen, augments water borne
diseases.
Any of the above or any combination of them
places the iris under stress. Light stress seems to be beneficial.
Shallow cultivation appears to cause a spurt of growth. The competition
of a weed trying to grow in a raspberry patch may cause it to reach
twice its normal height. A clump of irises run over by a truck may
recover with amazing rapidity. Scientists have known for some time that
stressed plants send salicylic acid as a signal causing the plant to
initiate its natural defenses – nicotinic acid, or whatever. If the
assault is moderate, the plant will build a partial immunity to the
injury. It has recently been shown through a study in which a bacterial
gene capable of salicylic acid transformation, was placed into tobacco,
that the usual immunity was not acquired. The authors concluded that the
immunity is dependent either upon the accumulated salicylic acid or to
protein expressed by genes activated by the acid. (Science 261,
754 (1993))
If however, the attack is severe relative to
the condition of the iris, the iris will go into scorch. The hypothesis
presented her is, then, that scorch is a condition rather than a
disease. It can be caused by many things, any of which, singly or in
combination, can cause the plant to scorch. It is stress that
causes an internal reaction in the plant. It is as if the plant says to
itself. "I cannot cope with this situation," and goes dormant
for a time.
The fact that the plant reacts favorably to
mild stress suggests that the initiating factor might be an auxin such
as gibberellic acid. It wasn’t long ago that this was on the market as
a week killer that acted by stimulating excessive growth.
If scorch is caused by some internal growth
inhibitor, it should be possible for one of our botanists or biologists
to come up with a counter measure that could save a lot of valuable
irises.
In conclusion I have hypothesized that scorch
is a dormant condition of a bearded iris rhizome (or a Louisiana iris)
brought about by stress. In response the plant generates a growth
inhibitor that kills all roots and top growth. Recovery occurs naturally
and usually within a period of one year.
It may be possible to accelerate the recovery
process as is done with dormant iris sees, by simply soaking in water.
We need not know the name of the inhibitor to experiment with methods of
amelioration. Wasn’t it the Aztec Indians who discovered that an
offering to the gods by including a piece of fish in each hill of maize
produced remarkable results? Growers can try such remedies as soaking
rhizomes in normal solutions (or even stronger) of salt, sugar,
household bleach, fungicides, germicides, alcohol, acetone, Rootone,
epsom salts, calcium chloride, sulphur, or whatever. A valuable rhizome
may be worth a try.
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This next article started out as a joke. We
were discussing routine business at our annual November Thanksgiving
local club meeting in Garden City. We talked about "hopping"
into a couple of vehicles and driving over to Johnson, Kansas to tour a
member’s garden next spring. She suggested we bring our shotguns for
rabbit control !!!!!!! She no longer has her dog and is now overwhelmed
with rabbits eating her iris foliage.
Sparked by the idea of chatting with others
from Region 18 in the electronic Internet group and by getting advice
other than shooting rabbits, I posted to the group. Responses were
received by the end of my day. Here are a few of them:
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Our moderator Judy Eckhoff
wrote: "… The furry little creatures are a problem for
me also. They don’t seem to eat on my iris but do love fresh
tulip greens and other tender plants. New shrubs were being
eaten to the point I had to put a fence around them. One thing
I’ve found to slow them down is to sprinkle garlic salt, hot
pepper sauce, etc. around the foliage. It helps. I now have a
cat and am seeing fewer rabbits."
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Sherryl Fitzpatrick wrote: " … When I
lived in Alabama, the rabbits would eat all my impatiens and tender
plants. I noticed they never touched my neighbors and she said she
sprinkled bloom meal around all newly planted plants. It really seemed
to work for her."
Jim Loveland - I could not
quote Jim but he added: Best way to deal with them … unless
of course you live in town you could get in serious trouble
shooting a gun. ….. Maybe sprinkle some nice cayenne on
moistened leaves …. Then watch them spit, dance or whatever
they do. Just have your digital camera handy so we can add
these pictures to the web site." Jim – here is that
picture!
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Jon Cliburn helped by saying: "At some
stores like Wal-Mart etc, or Sports shops that have hunting sections you
can buy small bottles of fox urine that hunters use to disguise their
human scent. Used sparingly, it will discourage the little critters, a
couple of pet cats or a dog will work also, but then there is nothing
better than rabbit & dumplings or fried rabbit!"
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Our RVP and Secretary Ray
& Judy Keisling posted: "Hi all – I will take fried
RABBITS (wrabits) over turkey (buzzard) any day for my holiday
meat anytime. We will take this opportunity to wish everyone a
happy Thanksgiving and hope that you have all your Iris
planted…. "
Steve and Jane Amy finished
the thread saying: "We sprinkled blood mean all around
one year. It’s great fertilizer also. We also had two labs
and a blood hound mix. The dogs thought that blood meal was
the greatest stuff. ….. I saw her (the black lab) hot on the
heels of a rabbit a couple times … Have a wonderful
Thanksgiving! I’m waiting for the picture of Nancy to come
out with her shotgun!"
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I can identify with lab (as in laboratory) and
with the blood since I am a "vampire" in a hospital
Laboratory. I posted back … to Steve … "you may be waiting a
mighty long time … it is pheasant season in SW Kansas right now. I’m
after birds right now. That sure would be a sight to see though …
I’ll see what I can do in the future. Happy Thanksgiving to everyone
…"
I sent everyone’s input to Joanne Snowbarger.
She was elated and I received back a very nice thank you card … with
Wrabbits pictured. Joanne is seriously thinking of getting another dog.
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