Wednesday, July 11, 2012

Rasberry crazy ant in urban gardens!

     I am concerned with what I observed at the Harris County Precinct 2 Master Gardener’s Genoa Friendship Gardens.  The Rasberry crazy ant [Nylanderia sp. nr. pubens (LaPolla, et al)] was observed nesting (larvae, pupae, and workers, and queens) in the leaves circling the shank of the corn ear.  This is the first time I have seen this ant nesting in a growing plant.  I have seen the ant crawling over plants but not actually nesting on the plant.


Rasberry crazy ant nesting on corn plant

Rasberry crazy ant nesting close to corn ear shank

Rasberry crazy ant under corn leaf
Rasberry crazy ant queen with worker ants on corn leaf
      For those of you not familiar with this ant, in 2002, Tom Rasberry, a professional pest-management provider from Pearland, discovered a population of a new pest ant near Pasadena, Texas, in Harris County. Huge numbers of this new ant literally covered the landscape in industrial parks and residences.  So the name has nothing to do with the raspberry but the name of the discoverer.    

     The Master Gardener’s commented that when some of the corn ears were being harvested the ant would emerge from the ears and run all over the arms of the one harvesting the ears.  This ant does not sting, though a slight bite may be felt with no after affects as compared to the painful sting of the red imported fire ant (Solenopsis invicta).  The person harvesting was constantly wiping their arms to remove the ant, and sometimes wiping their neck and face.

     One Master Gardener believes that the presence of the ant reduced the production of their corn plants but as mentioned on the Texas A&M Center for Urban Entomology web page devoted to the Rasberry crazy ant (RCA), “No information is available on potential yield effects in infested lands.”  There is no replicated data that would support this observation but there is information from the Global Invasive Species Database web page that in St. Croix Nylanderia pubens (very close relative to the RCA) has been blamed for crop damages due to high densities of plant feeding Hemiptera (aphids, mealy bugs, scales) that this ant has been observed tending.  The RCA feeds on the honeydew produced by these insects.

RCA tending aphids and feeding on drop of honeydew
Video of Rasberry crazy ant feeding on oak aphid honeydew

     I did observe a high number of aphids and a few mealy bugs under the corn leaves surrounding the ear that the ants could be tending.  Further observations/research on this would be enlightening.

Aphids on corn ear
Mealy bugs on corn ear
      My concern is with gardens in urban areas and other community garden projects that are present in urban areas where heavy populations of RCA are present.  First, the potential for the increased numbers of honeydew producing insects such as aphids, mealy bugs and scales will exist.  The ants protect these honeydew producing insects from other predators.   Second, movement of produce out of the garden areas would just be another avenue to spread the ant.  This could place urban garden projects in jeopardy.

     No testing has been done on products to control the RCA in gardens.  I would recommend that any attempts to control the RCA in garden areas should begin with procedures to limit the number of honeydew producing insects on garden plants.  These procedures may involve one or more of the following, 1) washing or wiping the insect off, 2) removal of infested parts, 3) using insecticidal soaps/oils, or 4) use an insecticide labeled for the specific insect and finally, 5) destruction of the plant may be necessary if the population of these plant feeding insects is too high.  Reducing the population of these honeydew producing insects may help in keeping the number of Rasberry crazy ants on garden plants to a minimum.

     If you do have this ant in your gardens, no matter what control procedures you use to keep the number of honeydew producing insects down,  wash all the produce before removing from the garden.  Corn should be shucked so as not to transport ants hiding within the leaves.  As the picture shows, queens can be present, and if you move a queen you move a population.  Be careful with these ants.

     For more information on the Rasberry crazy ant [Nylanderia sp. nr. pubens (LaPolla, et al)] and other urban insects please visit the Texas A&M Center for Urban Entomology web page.  For general information on the Texas A&M Department of Entomology please visit their web page.

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