Giant Ragweed

Weather has been a dominant force in the cycle of life at Blue Jay Barrens this year.  The range of conditions from flood to drought has disrupted the ordered flow of most seasonal events.  Drought continues to be the single most influential event of the year.  A recurring theme across the landscape is the reduced size of most plants due to lack of moisture.  Giant Ragweed is no exception, with the plants being about half their usual height.

The water starved plants try to rebound overnight, but there’s too little available moisture in the soil to do the plants much good.  Wilted leaves droop pathetically during the day.  Perhaps the hurricane remnants will pass through and help alleviate our water deficit.

Despite the dry conditions, the plants are blooming profusely.  The green and yellow flowers surrounding a tall spike at the top of the plant are hardly noticeable. 

Giant Ragweed produces separate male and female flowers.  Those flowers crowding the spike are all male and release a massive dose of airborne pollen.  Hay fever sufferers would definitely not be pushing in to get a close-up of these flowers.

Giant Ragweed is a native annual, so the plant must produce seed to ensure a future generation.  Female flowers are found concealed in leafy bracts growing from the leaf axils at the base of the flower stalk.  Most people don’t even notice these well hidden flowers. 

Typical Giant Ragweed leaves are three lobed like the one shown to the left above.  Many of the Blue Jay Barrens population are unlobed.

On of the most interesting features of the Giant Ragweed is the interaction between the Allegheny Mound Ants, Formica exsectoides and a Treehopper, Publilia concava.  Clusters of these insects are found on almost every plant.

The Treehoppers feed on ragweed sap and as a byproduct of the feeding process, produce honeydew.  The ants feed upon the honeydew.  In their efforts to protect their food supply, the ants provide security for the Treehoppers and the Giant Ragweed plant.

The Treehoppers are fascinating creatures.  The spiky nymphs exhibit a two-tone color pattern that is variable between individuals.  They certainly don’t look like something that is a likely food item.

The adult Treehoppers have a smoother appearance.  They stand out against the bright green of the leaf, but their wide variation in color patterns makes them appear to be a part of the plant.  These adults will overwinter in the leaf litter at the base of the plants and will emerge next spring to mate and begin new colonies.  I hope to always have a nice patch of Giant Ragweed for their use.

Redbud Treehopper

For many years I have enjoyed finding an abundant supply of these Treehoppers on the Blue Jay Barrens Redbud trees.  When I was young, finding Treehoppers was a real treat.  Being experts at looking like a part of the plant upon which they are resting, they never quite looked to me like real animals.  If they chose to move, it looked like the plant was rearranging its parts. 

Most have the general shape of thorns and make a normally smooth stem appear untouchable.  Knowing that the plant doesn’t produce thorns is what tips most people off to the presence of Treehoppers. Redbuds have smooth stems, so the thorns can’t be real.

Treehoppers pierce the stem with their mouth parts and feed on the sap.  Since their food comes to them, they don’t have to move around and they benefit by being mistaken for a stationary plant part.  Their numbers vary from tree to tree, but I’ve never seen so many as to cause damage to the tree.

A couple of years ago I decided to learn the name of this interesting insect.  I soon found it referred to as the Two-marked Treehopper, Enchenopa binotata.  Further reading indicated that the scientific name actually referred to a complex of species.  That didn’t make any sense to me.  It’s either a species or its not.  After more research, I gathered that there were several similarly appearing Treehoppers that were being assigned as different species because they were dependant upon different host plants.  This and several others had not yet been formally described and named.  So there’s no new name for me to learn and I can just keep referring to them as the Redbud Treehoppers.

Named or not, I find them interesting.  I’ve never seen them on any plant other than Redbud, so I must not have any of the other unnamed species.  I’ll keep watching them and maybe one day I can go out and announce that they are no longer nameless.

Ants and Treehoppers

These treehoppers are being protected by a squad of ants. In this case, it’s the Allegheny Mound Builder Ants providing the bodyguard service. These seem to be the dominant ants in the area.

Treehoppers penetrate the plant stem with their tube-like mouth and drink the sap. Like many insects that feed in this manner, the treehoppers discharge from their bodies a sugary solution called honeydew. Many insects are attracted to the honeydew, but it’s usually the ants that claim this bounty and aggressively defend the source.

When undisturbed, the ants spend their time collecting honeydew and tending to the treehoppers. If not taken by the ants, the honeydew will begin to grow mold that may cause the death of the treehoppers. The ants get fed and the treehoppers are relieved of a dangerous byproduct.

The slightest disturbance will cause ants to strike a defensive pose with antennae raised and mandibles open.

The collection of treehoppers typically consists of a few adults and many nymphs. The adults are winged and may leave to establish colonies on new plants.

Colonies can grow to be quite large. I found all of these colonies on Giant Ragweed plants. There was not one plant that didn’t have at least one treehopper colony.