Prevention
and Early Detection
Prevention and early detection are our best tools in stopping purple
loosestrife invasion and spread. Purple loosestrife should be removed
and destroyed by bagging plant material and allowing it to completely
dry out, by burning or burial, before disposing. Potential habitat should
be searched annually during July and August (peak bloom when easily
detected). Th e
discovery and early eradication of new infestations while still small
is both economically and environmentally cost effective.
Herbicide*
Careful use of herbicide has been proven to be an effective,
efficient, and the least destructive means of removing large purple
loosestrife stands. Available herbicides registered for use in California
are limited. The most widely used is spot treatment with Roundup and
Rodeo (glyphosate) at
a 1-1½ % solution, during early to late bloom.
The use of 2,4-D has shown inconsistent results. Garlon 3A or Renovate
(triclopyr), selective for broadleaved plants, has yet to be approved
for use in California.
*Follow
all label instructions when using herbicides.
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Flower removal
Where
plant digging is not feasible, removal of flower stalks helps retard
the spread of seed. A single plant can produce 2.7 million seeds
per year. Each seed can lay dormant for years in the soil before
germinating. Therefore, where removal of flowers is feasible it
is not a trivial exercise.
Cutting, Mowing, Fire,
Water Table Management
Many mechanical and cultural methods have been tried and have
proven ineffective in controlling purple loosestrife. In many
cases mechanical methods and controlled burns have resulted in
the promotion of further spread.
Hand pulling/digging*
Small patches of young plants can be removed by hand with
little effort. Mature plants are
difficult, but not impossible to remove by digging. The root mass should
be removed, making sure that ALL pieces have been collected. Purple
loosestrife will re-root from the tiniest of fragments. Dormant seeds
may
germinate because of soil disturbance during removal activity. For these
reasons, it is important to monitor the site for several years.
*To prevent the spread of seed, all work should be completed by mid-summer
before flowers go to seed.
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