Recently raised wild monarchs in Texas and reported Oe outbrakes in Texas

[JCW1925 at aol.com]

Re: Recently raised  wild monarchs in Texas and reported  Oe  outbrakes in 
Texas

Dear Harlan:

   We are located in the  Houston area (Clear Lake).  I have looked all 
around Houston for Ac but have not found any growing in the wild. Our last 
two winters as you know have been unseasonably warm.( no freezes) 
 
  At our farm we recently had a few wild Monarchs lay eggs on our potted  Ac 
milkweed plants that are kept in a green house.  I brought the egg laden 
plants indoors and raised the larvae on the Ac plant.  We did not find one Oe 
spore on the emerged and apparently healthy monarch butterflies.   So far, we 
have not had any problems with Oe. infections here in Clear Lake, Texas 
(Houston area)  The Ac plants, however,  were very healthy and free of  
disease or insects. I wonder if there are any other vectors for Oe other than 
adult Monarchs?   If any one has any data on this, please post to the list.

 We have formulated an artificial monarch diet that eliminates the problems 
(vector for Oe and other  larval diseases) associated with  feeding monarch 
caterpillars milkweed.  The diet works well and 5th instar larvae do not 
require supplemental milkweed.  

  For more information on our artificial monarch diet,  please visit our web 
site at www.educationalscience.com.  We also provide Monarch larvae 
(cultures) year round,  rearing kits,  pesticide-free milkweed plants, 
milkweed seeds by the pound, as well as insect rearing supplies, breeding 
cages, entomology kits and equipment, butterfly nets, and biotechnology 
education kits and equipment.

  We offer as a free service to our customers who have purchased livestock 
free screening for  Oe  spores.  Should any one in Texas require this service 
for free, please contact us at 1-800-299-6791 or at www.educationalscience.com

James Wiggins
Educational Science
www.educationalscience.com
Toll free: 1-800-299-6791
Clear Lake, Texas
(Houston, Texas  area)

  Below is a response by Dr.  Paul Cherubini, (entomologist/Lepidopterist) to 
Karan Oberhauser's  concern(s) about Oe  outbrakes in Texas.

Date: Tue, 19 Oct 1999 22:12:17 -0700
From: Paul Cherubini <paulcher at concentric.net>
Subject: Is this an accurate and tasteful response to Karen O.?

Dr. Karen Oberhauser wrote:

> There are have been several reports from TX on outbreaks of the protozoan
> parasite, Ophryocystis elekroschirrha (O.e.). 
> I don't want to be alarmist.

Many details were left out of your post. Details like the reports of
"outbreaks" involved only captive reared monarchs, not wild, free living
monarchs. Details like no published studies have shown the O.e. parasite
is lethal in free living monarch breeding populations whereas other
parasites like tachnid flies routinely kill 50% of monarch caterpillars
and chrysalids in the wild. Details like the purported outbreaks are
limited to the coastal areas of Texas, not the vast interior regions of
the State which are climatically unsuitable to sustain the growth of
A.c. So we're talking about a relatively tiny area of Texas where the
purported "outbreaks" are occuring (not the whole state and not the
central area of the state where the vast majority of fall migrants pass
through).
 
> It appears that most of these [outbreaks] are occuring in areas where
> non-native tropical milkweed (Asclepias currasavica) is 
> growing.  This milkweed is different from
> native TX milkweed in that it does not die back in the winter. 

Asclepias currasavica is not native to Texas, but it has become a
naturalised, wild growing weed in some coastal and extreme southern
areas of the state as well as in other southeastern states. Naturalised
A.c. WILL die back like the native Texas milkweeds if there is a winter
freeze and will send up new shoots in the spring like the native
milkweeds. Unnaturalised, nursery grown A.c purchased from garden center
type stores may die completely - roots and all - during winter freezes.

> Since the tropical milkweed [A.c] often occurs in gardens,
> it is watered and thus green during the summer when many native
> milkweeds die back due to heat and lack of water.  

Various posts to dplex in the summer months over the years indicate
Queen butterflies are common throughout Texas in the summer, hence there
MUST be significant amounts of milkweed growing in the hot, dry inland
areas all summer (possibly the Sarcostemma species which stays green in
the summer heat) Queens are even abundant in scorching Phoenix, Arizona
in mid-summer - a place where it is not unusual for temperatures to soar
above 120 degrees F. Sarcostemma is the primary host milkweed there.

> While it is exciting to have
> monarchs breeding year round in some areas in TX, I think that we should
> carefully monitor the impact of changing the monarch breeding cycle that
> has evolved over centuries.

Why monitor - what is there to be concerned, alarmed or worried about?
A.c. has been naturalised in south Texas for decades. How is it
conceivable that a few extra garden center purchased plants growing in
coastal home gardens are going to have more than a trivial impact
(postive or negative) of any kind on the eastern monarch migration
phenomenon? A.c. also occassionally grows wild throughout most of the
lowland areas of northeastern and central Mexico - even within 10 miles
of the overwintering sanctuaries in Michoacan.

> The eastern migratory population has low levels: less that 8% of
> adults are infected to any degree.  

8% of 150,000,000 eastern monarchs = 12,000,000 heavily infected eastern
monarchs flying around in the East and Midwest states. I've heard the
infection rate in eastern fall migrants may be as low as 1-2%, but that
still equals  1,500,000 to 3,000,000 HIGHLY infected butterflies flying
around and wintering in Michoacan.

> The western migratory population has
> higher levels, with about 30% being heavily infected. 

30% of 3,000,000 western monarchs = 900,000 heavily infected western
monarchs flying around the western states. The western USA is not
uniformly infected at the 30% rate. In some western breeding areas,
western monarchs are as "clean" as eastern monarchs. For example, your
research colleague, Dr. Sonia Altizer found NO heavily infected adults
in a sample of 42 adults collected by me in eastern Washington and
northeastern Oregon in early August 1997.

What's the big deal about any of these figures when infected butterflies
still apparently manage to live virtually normal lives - like I said, no
one has determined the O.e. parasite is lethal in wild monarch
populations. Heavily infected butterflies still migrate, overwinter,
mate and lay eggs.

> The non-migratory, continuously breeding poulation in southern FL has very 
high levels, with
> about 70% being heavily infected and almost 100% being infected to any 
degree.

My understanding is these south Florida populations wouldn't even exist
if A. currassavica hadn't been introduced to Florida by humans to begin
with. What "problem" are these heavily infected, but otherwise thriving
south Florida monarch populations causing for the wild migratory
monarchs that move into south Florida each year in the fall?

> The availability of milkweed throughout the year in TX may enable all of 
these mechanisms to affect
> parasite levels of butterflies...there is a chance that too much non-native 
milkweed in TX
> could have negative impacts on the eastern migratory monarch population.

Have you developed a model that could explain how high parasite levels
(if such levels really exist) in the few thousands or so monarchs
breeding in the fall and winter in home gardens along the Texas coast
could conceivably affect the parasite levels of the 150,000,000
migratory monarchs (in reporductive diapause) that pass through Texas en
route to Mexico? And affect parasite levels to what degree? Increase
them .00001%, 1%, 10%, 50%. And what is the biological significance of
any hypothetical increase in O.e. infection levels considering the O.e.
parasite is not known to be significantly lethal to wild breeding
populations of monarchs? 

> We could learn a great deal about this parasite, and possibly prevent human
> activities from having a negative impact on the eastern migratory
> population by carefully monitoring the situation in TX. 

What is your quantitative definition of a "negative impact"; a .00001%,
1%, 10%, or 50% increase in the percentage of infected butterflies in
the wild migratory or Texas winter resident breeding populations?,  
What is your impact risk standard; zero risk, negliglible risk,
significant risk, etc?
 
> Whenever possible, monarch watchers who have planted A. currasavica
> should collect larvae from these plants, and rear them to adulthood.
> All emerging adults should be checked for the parasite.

It wouldn't be surprizing if wild caught caterpillars reared in
captivity to adulthood will have spores because this "experiment" is
inherently designed to support a pre-conclusion; i.e. that O.e.parasite
outbreaks commonly occur in captively bred monarch caterpillars reared
on A.c. Rearing wild caught caterpillars in captivity to adulthood will
not explore a more important issue: determining if O.e. is significantly
lethal in unmanipulated wild populations of monarchs.

To explore this question, Texas coast Monarch Watchers could place a
screened cage over A.c. plants growing in the wild (or home garden) that
have larvae on them and check to see if the caterpillars and chrysalids
develope normally (or die from tachnid flies, ants, spiders and scores
of other predators!) This would still amount to captive breeding and
therefore still be somewhat unrealistic, but it would be more valid than
handling and manipulating the caterpillars in poorly ventilated cups or
jars in artificially illuminated, air conditioned buildings and feeding
them cut A.c  plants (inherently less healful than feeding the
caterpillars milkweed growing in the ground).

> We will be happy to work with any schools or individuals that would like to
> explore mechanisms and solutions to the problem of O.e. 

Even before experiments begin, it seems you have declared O.e. is a
"problem"- a problem not just in caterpillars raised in captivity, but
also in wild Texas monarch breeding populations that use  A.c. as a host
plant.

A Texas Monarch Watcher reported:

>"We confirmed the presence of the spores by noticing this last batch of
> adults did not emerge properly, about 90% were stymied in their pupal
> cases."

And another Texas MWer reported:

>"Yesterday we had 5 that began to emerge but could not "plop"
> out of the chrysalide and were stuck ... as if they had gotten dry."

And Karen responded:

> Only very high levels of infection cause these symptoms (ref 1);

My response to Karen:

Less than ideal larval handling and rearing practices (caterpillars
confined to poorly ventilated cups or jars in artificially illuminated
air conditioned buildings and feeding them less than optimally
nutritious cut A.c  plants) can also lead to these symptoms. The  MWer's
didn't say they counted the spores on the adults that (tried) to emerge
- one practical way to accurately determine whether or not they were
heavily infected.

> I don't want to be alarmist.  I think we can learn a lot from this, but I
> also think that there is a chance that too much non-native milkweed in TX
> could have negative impacts on the eastern migratory monarch population.

As I mentioned, A.c. has been naturalised for decades in coastal and
south Texas,  and southward into northeastern and central Mexico as well
as eastward along the gulf coast to Florida. Forty years ago Urquhart
reported winter breeding records in south Texas and northern Florida.

Paul Cherubini, Placerville, CA



Harlen E. and Altus Aschen      Port Lavaca, Texas   77979
mailto:
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Victoria Christian School (K-8)      Victoria, Texas   77901