As autumn slips
over the Neponset wetland
landscape...
Northern
Fowl Meadow, on the Hyde Park side of the Neponset River
off of Meadow Rd, Sept. '09.
...our
little beetles with the big appetites lie dormant,
waiting for spring. Beneath the rushes, the Sensitive
fern and the goldenrods, under the leaf litter
and along the cold mud of the wetlands, the new
generation of Galerucella rests up, dreaming of warm
weather and young Purple loosestrife shoots.
Interesting happenings
have come to light in the site monitoring data gathered
by Volunteers this autumn and last!
Data indicate
that after two consecutive summers
of beetle releases, Purple loosestrife at each
of our treatment sites (Brookwood Farm,
Milton-Fowl Meadow and Boston-Fowl Meadow) indeed is
showing the effects of the feeding beetles.
During
the 2008 growing season, the Purple loosestrife
("PL") plants grew shorter,
fewer in number, and sprouted many fewer
flowers (and shorter flower spires at that) than previously.
How is this significant?
To
deal with the Galerucella damage to their
leaves, the Purple loosestrife plants had
to expend energy to "heal" themselves and
re-leaf. They
diverted energy from efforts to grow
taller or to produce flowers. Result:
Shorter plants with few to no flowers. Because the
flowers on one PL plant can produce 2 million+ seeds, and
taller PL plants block the sun from nourishing potential
native plant competitors, this summer's shorter,
flower-less PL plants allowed more sunlight to
slip into the wetland to nurture potential
native competitors, and the
PL plants added far fewer seeds to the
wetland seedbank than normal. This is great news for our
efforts to reduce the grip of Purple loosestrife on the
wetlands and restore a diversity of native wetland
plants.
Interestingly,
Brookwood Farm showed the greatest impact from
Galerucella, this year. See the set of pictures
immediately below. At left, is Brookwood Farm,
covered in tall Purple loosestrife flowers in August 2008.
In the photograph at right is the same site, one year
later (August 2009). In the foreground of the 2009
photo. is a dusty-pink-flowered native plant called
Joe Pye-weed. Just beyond the Joe-Pye weed, and
in the distance, you see the yellow blooms of native
goldenrod species. The lavender-gray color in the center
of the photo consists of dead Purple loosestrife flower
stalks - remnants of the 2008 growing season. No
alive Purple loosestrife flowers are visible in
the 2009 photo. In fact, hardly any Purple loosestrife
plants at all flowered this season at Brookwood Farm. This
season's PL plants also were far shorter than
the 2008 plants, whose height is represented by the
year-old flower stalk remnants.
Brookwood Farm Purple loosestrife biocontrol treatment
site. Left: August 2008, right: Aug. '09.
Brookwood Farm. Left: Aug. 2008, covered in tall,
flowering Purple loosestrife. Right: Same site, Aug. 2009,
covered in the dead Purple loosestrife flower stalks of
2008.The living Purple loosestrife
The
next greatest impact from the Galerucella beetles was
evident at the Milton-Fowl Meadow wetland site, followed
by the Boston-Fowl Meadow site.
