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Because this is an ongoing and very active research program, we are interested in hearing from any observers whether they have seen evidence of this wasp, or other organisms causing damage to Arundo anywhere in the region. |
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 Presumably this is
not a native species, but perhaps was a hitch-hiker on Arundo when it was transported by Spanish settlers, although the wasp’s currently limited distribution may suggest that it’s a more recent arrival in the New World. Its larvae feed on the smaller diameter stems and shoots of Arundo (see photos), sometimes in numbers as high as a dozen or more larvae in a 10 cm section of stem. Mature wasps then vacate the plant, leaving small exit holes, which makes it fairly easy to see if the insect is present in a stand. The 4 mm long adult wasp lives outside the plant, and females insert their eggs into the stem of the plant. This life cycle can be repeated twice or more in one year. The adult population consists almost entirely of females, and since they do not need males for insemination, the potential for population growth can be quite large. In addition, the resulting damage fosters secondary infection by bacteria and other organisms that inflict further damage to the plant, sometimes killing the whole stem.
Initially one would suspect that since this herbivore is present, and so is a LOT of Arundo, that it must not be able to do a very effective job of controlling the host weed. However, mass rearing could allow us to produce much larger numbers of insects than normally are present in nature. The insects could then be distributed to attack more plants. There also may be means for enhancing the infections by promoting the microbes that cause the secondary damage. However, our best chance for biocontrol success may lie in bringing in additional insects, and hopefully specialized disease organisms as well, to knock out this extremely noxious plant.
Because this is an ongoing and very active research program, we are interested in hearing from any observers whether they have seen evidence of this wasp, or other organisms causing damage to Arundo anywhere in the region. Further information on the program is available at our website , including information on a parallel biocontrol program for tamarisk or saltcedar (Tamarix ramosissima). Email Tom Dudley or Adam Lambert.
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| Damage caused by a shoot-fly that also feeds inside Arundo stems. |
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