Thursday, July 12, 2018

Typhoid Mary and the Spongy Moth (formerly called the European gypsy moth)

Almost everyone is familiar with the name Typhoid Mary, or at least the connotation of the name. Poor Mary, she had no idea that she carried the bacteria that sickened at least 51 people and killed 3. She was far from the only, or even most destructive, carrier of this disease; there were unknown numbers of asymptomatic carriers (at least hundreds, probably thousands) and some of these were known to have infected large numbers of people. But Mary’s notoriety and resistance to accepting responsibility worked against her and she ended up living 26 years in forced isolation in a public hospital, until her death at age 69.

What does Typhoid Mary have to do with the Spongy Moth, Lymantria dispar, (formerly know as Gypsy Moth)? Nothing directly, perhaps, but they both first appeared in the Northeastern United States within a couple of decades of each other and both stories begin with one colorful and irresponsible character. For the origin story of the Spongy Moth, we have Étienne Léopold Trouvelot. Trouvalt was born in France, but came to the United States in his 20’s on the heels of political unrest in his homeland. He eventually settled with his family in a small town in Massachusetts, where the seeds of his entomological infamy were sown.

Spongy Moth Larva

Trouvelot was a man of many interests and, in the 1860’s, his eye turned to Entomology, specifically native silk moths of North America. In the course of his studies, for reasons known only to himself or lost to time, he went to Europe and returned with Spongy Moth egg masses. Showing an astounding lack of foresight, he began raising these insects on the trees behind his house. Of course, some of them escaped into the wild. The native North American trees were no match for these voracious leaf eaters and wholesale destruction ensued.

There are differing reports as to what happened after the moths escaped. Some say he warned the local authorities but no one followed up to capture or contain the insects. Others say that, although he was aware of the risk to the environment, he did not alert officials. What is clear is that shortly after this episode, he ended his experiments in Entomology and moved on to Astronomy (a seemingly perfect example of “out of sight, out of mind”).

Adult Spongy Moth
Trouvelat was a much more successful Astronomer than an Entomologist and became famous for his beautiful astrological illustrations. He was even made a faculty member at Harvard University and had a crater on the moon named after him. Clearly, his entomological debacle was quickly and successfully overlooked at the time.

In 1882, Trouvalt returned to France for good. This, ironically, coincided with the first Spongy Moth outbreak, which occurred right on the street where he had lived. By 1889, the Massachusetts State Board of Agriculture knew it had a serious problem on its hands and began a series of well-intentioned but unsuccessful eradication methods.

The wholesale destruction of hardwood forests by Spongy Moths continues to this day. Thankfully, their population growth and the ensuing outbreaks are cyclical and not constant. The Spongy Moth only produces one generation per year, which grows for several years (the years of outbreak) and then declines and then grows again. Outbreaks can last for up to 10 years for any particular area but, generally run 2-3 years.

While many methods of control have been tried, eradication has been elusive. The methods that include insecticides have proven too harmful for other living things. Some predatory wasps and flies that have been introduced; but, because they are not species-specific, they have caused serious damage to native moth populations. Luna moths and Giant Silk moths are two native species that are unintended victims of introduced parasitic wasps.

Some biological control methods that have been successful include:

Specific traps and lures as well as basic sticky traps are the still most widely used and effective controls around.

Horticultural and dormant oils can be used as smotherants. Bacillus thuringiensis kurstaki (Btk) can be applied to the caterpillar stage

The poor Irish cook, Mary Mallon, was vilified during her lifetime and made an outcast. The inept French entomologist gained accolades and 
fame while his destructive behavior was ignored. To this day, the majority of the information out there on Étienne Léopold Trouvelot relates solely to his Astronomy career. The reader can make his/her own conclusion as to how these two people have been treated so very differently, both in their lifetimes and in history.

Contributed by Pam at ARBICO Organics.

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