Purple Loosestrife invades wet habitats, cultural management techniques
are difficult to use. Vegetation should not be over grazed in or
near riparian areas. Sites without vegetation should be reseeded
to adaptable, competitive plants. However, purple loosestrife has
the ability to continue to invade even heavily vegetated sites.
This means that supplemental management methods are needed, in addition
to cultural. One effective cultural technique is to eliminate loosestrife
from ornamental plantings.
infestations of a few plants, purple loosestrife can be controlled,
especially on sandy soils, by hand pulling or digging seedlings
before they produce seed. More mature plants may require digging
to be uprooted. Remove all stems and roots by putting them in bags
to prevent them from sprouting new plants. Another mechanical method
is to cut flower heads before they seed.
species of beetles (Galerucella calmariensis and Galerucella pucilla)
are showing some promise for biological control of loosestrife.
Releases of at least 500 beetles per infested site are needed. These
beetles eat leaves, small stems, and flowers, and can completely
defoliate loosestrife plants. Two other insects, a root weevil (Hylobiau
transversovitatus) and seed weevil (Nanothyes spp.) are in early
For early season control of seedling and regrowth plants less than
1-2 feet tall, use aquatic-labeled 2,4-D is effective. Look for
seedlings where adult plants have grown.
Mature plants, the only labeled option is Rodeo at pre-flowering
to post bloom stages. For spot spraying use a 1.0 to 1.5% solution
plus .5% of nonionic surfactant. A wiper application can be used
with a 33.3% solution of Rodeo, plus 5 to 10% surfactant, at the
full-flower stage. Be extremely careful when applying Rodeo, it
is a nonselective product that will kill all other vegetation that
it comes in contact with. It is also recommended that all flowerheads
are removed and bagged prior to herbicide application. This will
reduce the amount of seed dispersal.
read and follow label instructions when making any application.
Consult with your local pesticide dealer or extension agent for
Management in Riparian Sites
or dig out small infestations. Apply a labeled herbicide to larger
infestations to reduce their size for mechanical treatment. Apply
2,4-D to early growing plants to avoid killing desirable vegetation
with use of Rodeo.