Kudzu and its Bug: A Tale of Two Invasives

 

Kudzu (Pueraria montana)
growing over trees.
Rowan County, North Carolina. 

Kudzu (Pueraria montana) is a famous, nay infamous, invasive vine from Asia.  It was introduced to the United States, like many invasive species, with good intentions.  It was imported as an ornamental plant in the late 19^th century and was used by United States Soil Conservation Service in the early 20^th century to control erosion in the south.  Kudzu is known as "the vine that ate the south" and grows over fields, trees, power poles and buildings. 

A trifoliate compound leaf of Kudzu.
Rowan County, North Carolina. 

Early spring Kudzu vine.
Rowan County, North Carolina. 

Twining vines of Kudzu.
Rowan County, North Carolina. 

Kudzu growing over a house.
Rowan County, North Carolina. 

Kudzu is a member of the Fabaceae, the pea family.  It has large, trifoliate compound leaves and hairy stems. Like many members of this family, Kudzu roots harbor nitrogen fixing bacteria that allows the vine to thrive in even the poorest soils. Kudzu has large tap roots resembling sweet potatoes that are rich in starch. In late summer, Kudzu produces inflorescences of beautiful purple and yellow flowers that smell of grape jelly.   In fall, Kudzu makes a hairy pod containing bean-like seeds.

A Kudzu inflorescence.
The inflorescence blooms from the bottom up.
Rowan County, North Carolina. 

A closeup of a Kudzu flowers.
Rowan County, North Carolina. 

Kudzu fruits.
Rowan County, North Carolina. 

While the plants do make seeds, Kudzu usually spreads by vegetative growth.  Stems that make contact with the soil make new roots and with a growth rate of a foot per day, the vines can ramble long distances in a single growing season.  Kudzu can kill other vegetation including large trees when the leaves and vines block out light and the roots outcompete other plants. 

Kudzu smothering trees.
Rowan County, North Carolina.

Control of Kudzu has proven difficult, and many methods have been tried.  Mowing a stand of Kudzu for several seasons or grazing with goats can remove the invasive plants.  Digging up the vines and herbicide application also works to get rid of Kudzu.  The aerial portions of Kudzu are killed by the first hard freeze and that makes a landscape of brown leaves and vines.  During the winter there is some decay of the dead vines but the following spring the plant begin its relentless growth again. 

A stand of Kudzu in winter.
Rowan County, North Carolina. 

In 2009 a new insect, Megacopta cribraia, started appearing in the counties around Atlanta, Georgia. This invasive insect is called the Kudzu Bug does feed on Kudzu, but it also causes severe damage to Soybean (Glycine max) crops.  Kudzu Bugs are true bugs in the Order Hemiptera and are native to East Asia, the same area that gave us Kudzu.  Kudzu Bugs are small, about ¼ inch long, dark brown and emit a foul, stinkbug-like odor when disturbed. Besides living on Kudzu and eating Soybean plants, this bug is also a pest around homes.  Kudzu bugs are attracted to white or yellow buildings and can congregate in large numbers on houses.  This new invasive insects probably arrived from Asia as stowaways on an airliner.  Since their arrival in 2009 Kudzu Bugs have spread out from Georgia and are now found from Texas to New Jersey and are a major concern for Soybean farmers.  

A Kudzu Bug (Megacopta cribraria) on a Kudzu leaf.
Rowan County, North Carolina. 

A group of Kudzu Bugs on a Kudzu leaf.
Rowan County, North Carolina. 

When Kudzu arrived in North America it found a favorable habitat with few natural enemies, and so it spread. Kudzu now grows from Florida to the Midwest and into Mid-Atlantic states. Contrary to some rumors, Kudzu Bugs were not intentionally introduced to control Kudzu.  Although the bugs do reduce the growth of the vine, it is unlikely this second invasive species will stop the march of  the "vine that ate the south".  

A Kudzu landscape.
Rowan County, North Carolina. 

Some Florida Notes

 

Juvenile Pied-billed Grebe (Podilymbus podiceps).
Green Cay Wetlands, Palm Beach County, Florida. 

Diane and I visited south Florida in August. It was hot.  The low temperatures at night were in the 80s and it went up from there.  These were not the best conditions for nature observation.  Birds were quiet and mammals were hiding out, but we went out each day to visit wetlands.  Even in these steamy conditions we saw some interesting sights. 

Adult Pied-billed Grebe feeding young.
Green Cay Wetlands, Palm Beach County, Florida. 

Many of the birds were still taking care of their last brood of the year.  An adult Pied-billed Grebe (Podilymbus podiceps) was teaching its two babies to catch fish.  The adult would dive, bring up a fish and drop it and let the juveniles try their hand at fishing.  This went on for at least 20 minutes and the fish was getting a little worse for wear by the time we left.  The young Pied-billed Grebes had a striking color pattern with gold, black and white stripes on their heads and pink at the base of their pied bills.  

Common Gallinule (Gallinula galeata).
Green Cay Wetlands, Palm Beach County, Florida. 

 

Adult and juvenile Common Gallinules.
Wakodahatchee Wetlands, Palm Beach County, Florida.

Common Gallinules (Gallinula galeata) and were also busy raising their young.  A baby Common Gallinule still had some downy black feathers and a partially bare head.  Its beak was yellow with a black mark and just a hint of red at the base.  The parent by contrast was dark gray with a yellow-tipped red beak.  Above the beak adult Common Gallinules had a red shield.  This structure is found in certain members of the Rail family, the Ralllidae, and probably functions in attracting mates.  Another striking feature of adult Common Gallinules was their legs and feet.  The toes are long allowing the birds to easily walk across floating vegetation.  The legs and toes are bright yellow with a red band near the body.    

An Black-bellied Whistling Duck (Dendrocygna autumnalis)
admiring the sunrise.
Green Cay Wetlands, Palm Beach County, Florida. 

Back-bellied Whistling Ducks (Dendrocygna autumnalis) were leading their latest offspring.   An adult was waddling through the shallows being trailed by a line of rather large ducklings. These handsome ducks have a gray head, brown body, a pink beak and, of course, a black belly.  The young ducks look much like adults but with a gray beak.  Black-bellied Whistling Ducks were formerly found in the American tropics but have expanded their range through the southern and eastern United States and north into Canada. 

Adult and juvenile Black-bellied Whistling Ducks.
Wakodahatchee Wetlands, Palm Beach County, Florida. 

Least Bitterns (Ixobrychus exilis) are the smallest of our herons.  They have short necks and short legs and spend their time hiding among the reeds.  It is rare to get a good look at one of these shy waders so the day we saw three was a real treat.   A family group was working their way across a marsh jumping between the rushes (Juncus sp.) then flying across short gaps of water to disappear again in the vegetation.

 

Least Bittern (Ixobrychus exilis).
Green Cay Wetlands, Palm Beach County, Florida. 

Dragonflies were active in the summer heat.  These voracious predators flew across the marsh searching for insects and would briefly perch on the tips of plants. Brilliant Blue Dashers (Pachydiplax longipennis) were common with their bright blue bodies and emerald eyes.  

A male Blue Dasher (Pachydiplax longipennis). 
Green Cay Wetlands, Palm Beach County, Florida. 

Four-spotted Pennants (Brachymesia gravida) were abundant in the marsh. Their common name comes from the dark spot on each of the dragonfly's four wings.  They also have a small white spots called stigma on the leading edge near the tip of the wings.  

Four-spotted Pennant (Brachymesia gravida).  This is
a female with light brown wing spots. 
Green Cay Wetlands, Palm Beach County, Florida. 

The most dramatic dragonflies we saw were the Halloween Pennants (Celithemis eponina).  The males are orange with brown wing spots.  This color pattern is reminiscent of Halloween decorations and gives the insect its name. Females are a little less orange but still have the dark wing spots.  Halloween Pennants have the curious habit of perching with their front and back wings held at different angles. 

Halloween Pennant (Celithemis eponina). 
Green Cay Wetlands, Palm Beach County, Florida. 

Halloween Pennant.
Green Cay Wetlands, Palm Beach County, Florida. 

On a boardwalk that crossed a pond, we saw feathers floating on the water.  The first feather was a primary, white with a black tip. It was from a White Ibis (Eudocimus albus).  I thought it had been dropped by a molting bird since they replace their feathers after the breeding season.  Then other feathers started drifting by.  There were more primaries, then secondaries, then body feathers.  This peaceful sight of floating feathers started to look like something darker.  Like leftovers from an alligator's meal. 

White Ibis (Eudocimus albus).
Wakodahatchee Wetlands, Palm Beach County, Florida. 

White Ibis primary feather floating.
Green Cay Wetlands, Palm Beach County, Florida.

White Ibis body feather floating.
Green Cay Wetlands, Palm Beach County, Florida. 

It was fun going out on those slow, hot Florida days.  Several people told us, “Come back in October, when the weather is nicer.”  We will.