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Jack-in-the-Bush Leafminer (Might Take Ten Years Off Your Face)

Starring  Chromolaena odorata as the plant

(Chromolaena means colorful cloak.  Odorata denotes fragrance.)

Asteraceae (Aster Family)

With Cremastobombycia chromolaenae as the miner

(Cremasto means suspended.  Bombycia means reed, or flute made of reeds.  Chromolaenae refers to the plant host.)

Gracillaridae (Leaf Miner Moths)

Today’s botanical hotspot was the Jupiter Ridge Natural Area at Jupiter, Florida, a large sunny scrub with a marsh in the middle, plus a tidal creek.   Habitat diversity translates into biodiversity, making the site a great place to go.    The pretty flowers today were escaped horticultural water lilies in pink and blue, picture perfect and fragrant abuzz with bees, but we’ll feature a more mundane creature.   Leafminers were at work, and intriguing if not eye candy.  Leafminers are larvae of various insects trapped for a portion of their youth tunneling through leaf tissue, feasting on salad protected from the harsh world.  Arthropod boarding school.

Chromolaena odorata 1

Jack-in-the-bush by John Bradford

The most conspicuous of the miners at this season infests a large native weed coming into its Holiday blossom time, Jack-in-the-Bush.  Its miner-miner 49er has two remarkable truths:

  1. The insect ducked formal “discovery” until 2013. (Nobody cares about a worm in a weed.)
  2. The larva is not satisfied with a mere tunnel. Instead, it excavates a huge white blotch separating the upper epidermis (skin) from the tissues below.   Sometimes the blotch covers the entire leaf surface.  A heavy infestation resembles ornamental variegation.
leaf miner larva in mine

Blotch with culprit. The miner is under the epidermis.

You might wonder how a tiny caterpillar can undermine a big area.   It swings its head vigorously from side to side like a reaper with a scythe.

Watch the little swinger here:  CLICK

At this juncture the discussion broadens from the single species pair to miners in general, remembering how they represent diverse major insect groups.  So what I’m about to say applies to some but probably not all.     Leaf miners have a problem…they might outlive their host leaf.

Chromolaena odorata 7

By JB

Heaven forbid, what happens if the leaf ages and drops before the little feller completes its tunnel time?   That brings us to the botanical anti-aging hormones, cytokinins (SIGH-toh-kine-ins).

cytokinin creme

I doubt cytokinins  are a fountain of youth on human epidermis, but they do work on plants.

CLICK here

If you are a parasite  inhabiting a leaf, you wish your blade a long healthy life.   Leaf miners do more than just wish, they promote foliar youth and longevity.  Although I have trouble finding convincing photogenic examples in South Florida, farther north where leaves seasonally discolor and drop,  leaf miners release cytokinins to insure their home, or at least the miner’s mineshaft region.   Such green areas housing miners surrounded by deteriorating leaf tissues are called green islands.   CLICK to see one.  The miner is at the lower right corner of the island.

We must wonder if the miner is merely protecting its lair from routine leaf aging.   Alternatively (or additionally), perhaps the life-extending hormone therapy mitigates the miner’s damage.

It gets more complicated.  Does the miner make the cytokinins, or does it cause the leaf to?   Or maybe neither:  There is a third factor in the equation;  it seems the miner can’t prescribe the cytokinin rejuvenation without the help of symbiotic bacteria.  In short, all three species are involved: bacteria, insect larva, and plant.

miner larva exposed

Exposed!

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For those wishing to burrow deeper: MINE THIS

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Posted by on December 8, 2017 in Leaf miners, Uncategorized

 

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Lazy Jack Hanging in the Bush

Jack in the Bush, Siam Weed

Chromolaena odorata

Asteraceae

John is away for a couple weeks so I must represent alone, although that’s easy after a week of class field trips.   A curious species often encountered in class is Jack in the Bush, a native with a big personality in disturbed places, usually sunny. It is a native in Florida but a mixed minor blessing and major horror escaped invasively around the tropical world.

Jack with violet flower heads (by John Bradford)

Jack with violet flower heads (by John Bradford)

A problem with deliberately introducing plants and beasts—and in some marriages—surfaces when minor blessings later turn into major horrors.   Jack in the Bush has spread far and for different reasons, including during WWII on equipment and personnel, as a living mulch, as a cover crop, and in coffee plantations.   Why is it deliberately spread?   The robust growth crowds out other weeds, is reportedly allelopathic (naturally herbicidal), insect and nematode repellant, and easily generated green manure. It is beneficial to some fallow fields. And being so utterly willing to grow anywhere, our species has attracted attention as a potential cover for mine tailings. Hooray. Bring it!

Jack with white heads (JB)

Jack with white heads (JB)

Too bad it grows too well, and in Africa, India, Asia, and beyond Jack has gone crazy, dominating farm fields, disrupting cropping cycles, invading tree crop plantations, and becoming a general smother as well as hosting pest insects and probably pest fungi. The leaves are petri dishes hosting powdery mildews and many other fungi. Researchers have found the soil near Chromolaena to be oddly high in the spores of certain molds, as if somehow promoting them.

Derisive common names are revealing, such as “King Kong,” “Cholera,” and Rey de Todo (King of Everything) reflecting an imperialistic tendency to form vast single-species stands.

Rey de Todo (See how it looks wilty?)

Rey de Todo

This plant knows how to grow. Is it an annual or perennial? Both. Whatever top growth survives drought, fires, grazers, and mowers from year to year resprouts from buds.   It can regrow directly from the roots, which can enlarge into immortal storage organs, and from tiny seeds (achenes) blowing forth on parachutes to new colonization opportunities as crowded as 2000 seedlings per square meter. Once the growth starts, stand back, as observers have noted, “it grows like a crop.” If the main stem finds a support it can shoot up to 30 feet. If no support is encountered, side branches take over, often growing out at right angles. Growth rates can exceed an inch a day.

The flower heads have an odd trait: variable coloration, whiteish, bluish, violetish, and pinkish. That might tie in with the dozens of butterfly and moth species recorded to visit and pollinate. With so much help the plant can establish anywhere. And who needs butterflies anyhow? It reportedly can set seeds clonally without benefit of bugs.

The plant is wilted when nobody else is.

The plant is wilted when nobody else is.

Reluctant to stand on its own two feet, Jack is sort of a shrub, sort of an herb, and prone to sprawl across and climb more substantial shrubs.   Why form wood when others do it for you? Cut open the stem, even a big one, and you find it to be made disproportionately of pith, soft, cheap, air-filled “styrofoam,” easy, lightweight, and fast to make, and of no substance.

The stem has more soft but useless pith (white) than supportive water-conducting wood (light green).

The stem has more soft but useless pith (white) than supportive water-conducting wood (light green). “Quick & Dirty” No wonder it flops.

That probably explains why Jack in the Bush so often looks wilted.   Water travels in wood (xylem), not in pith (parenchyma). So if your stem is super pithy and deficiently woody, you probably can’t move much water. If you can’t move much water you could spend a lot of time wilted. Ecologist K. Naidoo discussed “severe wilting” of Jack in the Bush as a probable adaptation to help with water use efficiency and avoid leaf damage at times of water stress.

There’s an apparent trade-off in play, just speculating.   Lightning fast growth at the cost of building a soft flimsy stem with minimal water-conducting wood. Let the host plant supply the support, grow like mad when there’s plenty of water, and take it easy wilted in the meantime.

 
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Posted by on October 24, 2015 in Jack in the Bush

 

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