Wednesday, September 30, 2015

The monarch expert weighs in on tropical milkweed

Should we or should we not plant tropical milkweed (Asclepias curassavica)?  

Dr. Lincoln Brower, the world's foremost monarch butterfly expert, answered the question in his January 2014 essay, "On the wisdom or lack of wisdom in planting Asclepias curassavica outside of its normal range."

Asclepias curassavica is a tropical American milkweed and its natural distribution is Mexico, Central America, South America and the Caribbean (see Woodson 1954 reference below). It is very likely that curassavica has been intimately involved with the long term evolutionary history of the monarch butterfly in the Neotropics but NOT in the temperate zone. In that sense, allowing curassavica to reproduce in North America is encouraging an exotic weed. 

I have cultivated curassavica in a greenhouse at Amherst College in Massachusetts, in a large milkweed garden at the University of Florida in Gainesville, and at my former home near Gainesville. It is an ideal food plant of the monarch butterfly and is cultivated extensively to maintain commercial and experimental monarch cultures.  However:

The first problem with planting curassavica is that monarchs are highly attracted to it, lay their eggs and usually overwhelm the plants with caterpillars.

The second problem, and a more serious one, is that when monarchs are in their non-reproductive phase (gonads repressed in the fall), they will be almost irresistibly attracted to curassavica, remain near the plant, and come into reproductive condition. When this happens, as far as we know, monarchs lose their migratory urge.......and probably, as individuals, never get it back.

Evidence of this was dramatically demonstrated in Gainesville. I had about 50 well developed potted curassavica plants that I set out in my yard and another 100 or so that we planted in a garden at the University.  Fall migrants were highly attracted to the plants, laid eggs and there were so many caterpillars that I had to cull them.  At home where I kept a closer eye on them, the migratory monarchs produced an early fall generation and their offspring then produced a second generation.  The caterpillars formed their chrysalids by the dozens under the eaves of my house. By then it was mid- to late November, and the temperature cooled down, slowing development. Then a frost occurred and 100 percent were killed in the chrysalid stage. (Gainesville generally has two or three killing frosts each year.) I had this happen over several years.

I also visited an enormous county milkweed garden near Tampa, Florida, in the fall, and the monarchs had completely stripped hundreds of the curassavica plants. Since all native Asclepias die back in Florida, what could the butterflies then do?

Another problem with establishing what becomes a continuously breeding population of monarchs is that the incidence of the protozoan parasitic disease (Ophryocystis elektroscirrha) increases with time. If the diseased individuals then somehow end up breeding with or joining the overwintering clusters of monarchs, then the incidence of the disease will very likely rise with detrimental effects on the migratory monarch populations.

Professor Sonia Altizer at the University of Georgia, who is the world expert on OE, agrees with me.

I would limit curassavica to be used in inside demonstration projects, growing the plants in an enclosed area totally inaccessible to the wild monarchs.


Altizer, S.M., Oberhauser, K.O., and Geurts, K.A. 2004. Transmission of the protozoan parasite, Ophryocystis elektroscirrha, in monarch butterfly populations: implications for prevalence and population-level impacts. In: Oberhauser, K.S. and Solensky, M. (eds). The Monarch Butterfly: Biology and Conservation. Cornell University Press.

Woodson, R. E., Jr. 1954. The North American species of/ Asclepias/ L. Annals of the Missouri Botanical Garden 41: 1-211.

Monday, September 28, 2015

A crabby crab spider

This male crab spider, which showed up on our dining room floor yesterday, did not want to cooperate and demonstrate his crab-mimicking skills. Maybe some other day. 

The cycle of life

This is when a blog comes in handy. I saw this black wasp go underground yesterday in the back yard and managed to get one shot as she was emerging, likely from laying and/or tending eggs. So then my inquiring mind wants to know what kind of wasp is she? So then I get online and do a quick Google search for a black wasp with yellow spots. Then my memory kicks wasps on mountain mint. Ah HA! Now I remember! And a past blog post of mine confirms that she is a blue-winged wasp (Scolia dubia), a species which I photographed last June ("Blue-winged what?"). Cool! These wasps nectar AND reproduce in our Wildscape.

Mini bird baths

The chickadees and titmice think the ant moats on our hummingbird feeders are their personal drinking stations.

Ironclad beetle

I spotted this one circling around on a bird bath. Hope it figured out where it wanted to be!

More what's blooming

 Photos don't do justice to the black dalea and snapdragon vine
 Snapdragon vine 'Red'
Plateau goldeneye (Viguiera dentata) is just beginning to flower
 So is the fall aster

 My sweet parralena (Thymophylla pentachaeta) in the street
Prairie broomweed in the Meadow

Look closer....

One of my favorite native plants in our back yard is the velvet-leaf mallow. It's taller than I am now! And like its name implies, the leaves are velvety soft. I had my point-and-shoot yesterday evening and happened to spot a small crab spider lurking on a mallow bloom. So I snapped. Then I kept looking, closer and closer. I must have circled the mallow at least three times. See if you can see what I saw.....

Sunday, September 27, 2015

Tropical milkweed or not?

The debate continues. Should we plant tropical milkweed (Asclepias curassavic) for monarchs or not? Yesterday, I observed an entire flower bed neatly planted with the species at Mueller Austin,  a high-density development designed with sustainability in mind. After attending last weekend's Texas Pollinator Powwow in Kerrville, I'm of the opinion that we should not this species. 

That's because I listened to Dara Satterfield discuss research findings related to the nonnative species. She's with the Monarch Health Project, a citizen science project being conducted by Satterfield and other biologists with the University of Georgia. 

According to the project's website, participants "track the prevalence of the protozoan parasite Ophryocystis elektroscirrha (OE) in monarch butterflies. This parasite does not infect humans but can make butterflies sick: Monarchs infected with OE may be too weak to emerge properly from their chrysalises and can die at this stage. Or, infected monarchs can look completely normal but cannot fly as well or live as long as healthy monarchs."

What the research is showing is that "tropical milkweed in warm areas can encourage OE," Satterfield said last weekend. To protect monarch health, she also said, cut the tropical milkweed to the ground in the fall and even cut it monthly until spring. 

What I took away is that we should plant only regional milkweeds. Better yet, plant native milkweeds from seeds that originate in your area. I confess that I haven't adhered to that strictly. In fact, at the Powwow I bought an Asclepias tuberosa, which is native to Texas but not Central Texas.

After James and I got home from Kerrville, I cut our two tropical milkweeds nearly to the ground. I may even pull them up. I just haven't  quite decided yet....... 

New additions

So I have more new friends to plant. These came home with me from last weekend's Pollinator Powwow. I bought the beebrush and nettle from Randy Johnson Organics and the remainder from Medina Garden Nursey.

Beebrush (Aloysia gratissima)
Butterflyweed (Asclepias tuberosa)
Possumhaw (Ilex decidua)
Fragrant mistflower (Chromolaena odorata)
Smallspike false nettle (Boehmeria cylindrica)

Wanna see a giant redheaded centipede?

Here you go! A real, honest-to-goodness giant redheaded centipede (Scolopendra heros), which must have measured at least 8 inches long. A friend here in Blanco found it in her yard and captured it in a lidded, plastic pail. I got some photos, then James and I released it near a local creek away from people. Is this species dangerous to humans? Can its bite or sting be fatal? For more information, you can read Ben Hutchins' short species profile, "Stuff of Nightmares," that he wrote for Texas Parks & Wildlife magazine.

Cenizo blooming again?

YES! Our dwarf cenizo in the back yard is blooming yet again! It just bloomed earlier this month. Many of the cenizos in the area are blooming as well. A hopeful sign of rains to come, eh?

Friday, September 25, 2015

What's blooming

Betonyleaf mistflower (Conoclinium betonicifolium)
Salvia 'Otahal'
American beautyberry
Gray goldenrod (Solidago nemoralis)
Common sunflower (volunteer)
Black dalea (Dalea frutescens) and snapdragon vine
Texas nightshade
Velvet-leaf mallow
Old-man's-beard finally blooming!

One tough little crab spider