When
78,000 Japanese ladybugs left the shelter of NJDA’s
beneficial insect laboratory in Ewing last year
to wage war against the hemlock woolly adelgids
destroying the state’s native hemlocks, the
big question was how they’d manage over the
New Jersey winter.
But
the news is great! Surveys conducted this month confirm
that the imported beetle did overwinter in the Garden
State and has now established colonies in several
locations. Additional releases have already been
made this year in the state’s hemlock stands
to bolster the predator’s numbers against the
pest.
The
imported ladybug eats only adelgids and will not
compete with native ladybugs. Only time will tell
whether the Japanese ladybugs will be able to control
the adelgid infestation and save the remaining hemlock
forests.
Hemlock
woolly adelgid, a destructive insect, is native to
Japan and China but was accidentally introduced into
the eastern United States a few decades ago and has
spread throughout the northeast. The female adelgid
lays her eggs in a woolly mass near the tips of the
branches. The adults and nymphs feed on the sap of
the tree, removing nutrients and causing the tree
to weaken and die.
The
adelgid causes so much damage because it has no natural
enemies here to help keep it under control. Although
a number of natural and synthetic chemicals are available
to control this pest in nurseries and in domestic
landscapes, it is virtually impossible to use them
in natural hemlock stands. The natural stands are
difficult to reach on foot and the infected trees
live beneath dense evergreen canopies that can’t
be penetrated by aerial chemical applications. NJDA’s
beneficial insect laboratory began producing the
ladybugs in 1997 from stock collected in Japan by
the Connecticut Agricultural Experiment Station.
This insect production initiative was conducted in
cooperation with the USDA Forest Service (USDA/FS),
the New Jersey Bureau of Forestry and the Connecticut
Agricultural Experiment Station. Under a cooperative
agreement with the USDA/FS, this year NJDA will also
supply a number of other northeastern states with
laboratory-raised beetles for releases in infested
hemlock stands in those states. Research continues
in an effort to find additional beneficial insects
that prey on hemlock woolly adelgids. |