An American Tail: the Lotus and its Caterpillar

Authors
Published on

If you're in Greater Cincinnati and have the chance visit the beautiful Glenwood Gardens [Great Parks of Hamilton County], grab a map at the main office and ask how to hike to the "Lotus Pond."  It's a bit of a hike, but do what I did and wait until the afternoon temperature climbs above 90 F. and the humidity allows you to wear the air.  Who needs a sauna?

 

American Lotus

 

Your intrepid perseverance may be rewarded by a display of American lotus (Nelumbo lutea). It's one of my favorite native wildflowers and is also known as water-chinquapin and yellow lotus.  In my opinion, there is nothing else that rises from our waters to rival the allure of this aquatic beauty.

 

American Lotus

 

Fragrant yellowish-white flowers (lutea means yellow) opening up to 10" wide.  Deep green exotic-looking leaves stretching almost 3' in diameter.  What's not to like?  Even the showerhead seed pods draw interest.  Of course, there are those who may not share my enthusiasm for this native aquatic plant, but more about that later.

 

American Lotus

 

American Lotus

 

There are only two species of lotus worldwide:  the American lotus and the sacred lotus (N. nucifera) which is also called the Indian, Asian, or pink lotus.  Both lotus species once belonged to the water-lily family, Nymphaeaceae, in the plant order Nymphaeales. 

 

However, based on DNA sequencing, the lotuses are now placed in their own family, Nelumbonaceae, and moved to a different order, Proteales.  This order also includes the plane family, Platanaceae.  This means American lotus is more closely related to American sycamore (Platanus occidentalis) than it is to any of the water-lilies.

 

American Lotus

 

The apparent similarities between lotus and water-lilies are now considered the result of convergent evolution where natural selection produces comparable features among unrelated or distantly related organisms.  A frequently used example are bats, birds, and insects all having wings. 

 

American lotus colonies spread by seeds and submerged rhizomes.  The plants are not free-floating; they are firmly rooted in submerged soil.  That's why plants grow around the edges of ponds or in the shallow waters of lake inlets or river backwaters; oxbows are a favored location.

 

American Lotus

 

The large lotus leaves are coated in epicuticular waxes.  I've always appreciated how droplets of rainwater that collect in the leaf centers glisten gem-like in the sun.  The leaves and stems have milky sap which has a number of interesting attributes including alkaloids that have been shown to have anti-bacterial properties.

 

American Lotus

 

American Lotus

 

The lotus plants provide a healthy habitat for a wide range of micro and macro-organisms.  The large leaves protect immature fish from predators, the seeds are utilized by ducks and other migratory birds, and the rhizomes are eaten by beavers and muskrats.

 

American lotus can be enjoyed in a number of locations around Ohio beyond Glenwood Gardens.  You can find it growing in shallow inlets along Lake Erie as well as Tappan Lake in northeast Ohio and in the shallow upper reaches of Cowan Lake located just southwest of Wilmington, OH.  Indeed, there was once a trail in Cowan Lake State Park called "Lotus Cove."  However, while lotus continues to grow in the lake, the cove is choked with silt and the trail is now defunct.

 

American Lotus

 

Not everyone views American lotus with the same appreciation.  Although native, it can be aggressive in colonizing shallow waters creating a challenge to those who pursue other aquatic beauties such as bass, sunfish, etc., and aquatic activities like boating and water skiing.

 

American Lotus

 

American Lotus

 

 

Some Lotus May Be Sacred

Don't confuse American lotus with its non-native cousin; the sacred lotus.  Unfortunately, this lotus has found its way into some Ohio waters which is why it is included in the Ohio Field Guide to Aquatic Invasive Species.

 

The color of the flowers provides a helpful way to tell the difference between our native lotus and the non-native sacred lotus.  American lotus flowers are yellow to yellowish-cream colored.  Although there are a few varieties and cultivars of sacred lotus that also produce light yellow flowers, most produce flowers that are pink or tinged with pink which is why it's sometimes simply called the pink lotus.

 

Sacred Lotus

 

You can learn more about identifying invasive aquatics in Ohio including the sacred lotus by clicking on this hotlink:

http://ohiodnr.gov/Portals/wildlife/pdfs/species%20and%20habitats/OSU_AIS_FieldGuide_Web.pdf

 

 

 

The Caterpillar

The American Lotus Borer (Ostrinia penitalis (Lepidoptera: Crambidae)) can be a significant pest of American and sacred lotus in Ohio.  The most obvious symptom is the skeletonizing-like leaf damage that's currently giving a ragged appearance to lotus leaves in Cowan Lake and in the Glenwood Gardens Lotus Pond. 

 

American lotus borer

 

The caterpillar is found throughout North America as well as the Amazon basin of South America; the same range as its American lotus host.  The moth has two generations per season in Ohio.  The current leaf damage is being caused by the first generation; damage by the second generation is typically more severe.  Despite its common name, the borer has also been found feeding on various smartweeds (Polygonum spp.). 

 

On lotus, early instar caterpillars are found on the upper leaf where they use silk to pull together two radiating leaf veins creating a shallow trough-like depression.  Individual caterpillars reside within these depressions covered by a dense mat of silk which presumably prevents them from falling into the water and provides camouflage against predators.  The ruse is not always effective as there are reports of redwing blackbirds shredding leaves in search of the caterpillars.

 

American Lotus Borer

 

The caterpillars feed beneath their webbed abodes and also venture forth, apparently mostly at night, to feed on the surrounding leaf surface.  During this time, the caterpillars remain anchored to the leaf with silk; an adaptation to their aquatic environment preventing them from being washed away by waves.

 

American Lotus Borer

 

American Lotus Borer

 

American Lotus Borer

 

True to their common name, as the larvae mature, they eventually change their feeding habits to become borers.  The caterpillars burrow into the leaf petiole where the petiole attaches to the leaf and feed by tunneling down the petiole.  Their stem boring activity isn't just confined to the leaf petioles.  The caterpillars also tunnel the flower stems to eventually find their way into the seed heads.  In fact, this is where the second generation larvae pupate to spend the winter.

 

American Lotus Borer

 

American Lotus Borer

 

There are records of the borer causing serious damage to all parts of its native and non-native lotus hosts including significantly reducing seed production.  Indeed, I observed severe leaf damage to the lotus in Cowan Lake.  Other than physically removing the caterpillars from the leaves and stems, there are no other effective controls. 

 

American Lotus Borer

 

Fortunately, as with any native insect, populations tend to rise and fall dramatically from year to year, so the borer seldom causes significant long-term damage to a colony of American lotus.  It appears that established American lotus colonies have the ability to recover from the periodical onslaught by its caterpillar.