Steel Blue Woodwasp (Sirex noctilio)
Steel Blue Woodwasp (Sirex noctilio) is native to Europe, Asia and northern Africa where it attacks Scotch pine
(Pinus sylvestris), Austrian pine (P. nigra) and maritime pine (P. pinaster) almost exclusively. However, this
wasp has been introduced into New Zealand, Australia, Uruguay, Argentina, Brazil, Chile, and South Africa where
it attacks exotic pine plantations and can cause upwards of 80% tree mortality. Other susceptible pine species
include Monterey (P. radiata), loblolly (P. taeda), slash (P. elliottii), shortleaf (P. echinata), ponderosa
(P. ponderosa), and jack (P. banksiana).
The lifecycle of Sirex woodwasp in the United States is expected to be a single generation per year.
Adult emergence is likely to occur between July and September, peaking in August. The female wasp is
attracted to stressed trees where she drills into the outer sapwood with her ovipositor and injects a
symbiotic fungus (Amylostereum areolatum), toxic mucus, and eggs. The female may lay from 25-450 eggs.
The mucus and fungus kill the tree, which creates a favorable environment for larval development.
The number of larval instars ranges from 6-12 and all instars feed on the fungus as they tunnel
through the wood. The larval stage generally takes 10-11 months. Following pupation near the bark
surface, adults emerge from 1/8-3/8" diameter holes approximately three weeks later.
Ohio has extensive hardwood and evergreen forest types. Native pine species include jack, shortleaf,
pitch (P. rigida), scrub (P. virginiana), and eastern white pine (P. strobus). Jack pine is native
to the northern lake portion of Ohio and eastern white pine is native to a portion of the northeastern
section of the state. Shortleaf, pitch and scrub pines are native to southeastern Ohio. Non-native
Ohio pine species include Austrian, Pondersosa, red (P. resinosa), and Scotch. Between 1995-2003 ten
S. noctilio interceptions were made in solid wood packing materials (SWPM) from Spain and Italy, and
two interceptions on logs and 'cargo' from China. Additionally, siricid wasps have been shown to
follow the pathway of wooden handicrafts from Asia and Mexico. Sirex noctilio is already well
established in the eastern half of upstate New York, and has recently been detected in 7 counties
in north-central Pennsylvania, including Erie county on the Ohio border, as well as 4 counties in
Michigan along the eastern border with Ontario, Canada and lake Huron. Given Ohio's native and non-native
pine forests, the economic and ecological impact this pest could have on the state, and the proximity of
the New York, Pennsylvania, and Michigan detections to the Ohio border, this pest was surveyed in 2006
and 2007. No detections were made in either year.
If you suspect you have found a Sirex infestation contact the Ohio Department of Agriculture
Plant Pest Control Section.
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