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Purple Loosestrife


Loosestrife Infestation


Since 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.

Mechanical management

For 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.

Bagging Purple LoosestrifeBiological Management

Two 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 research stages.

Herbicide Management

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.

For 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.

Always read and follow label instructions when making any application. Consult with your local pesticide dealer or extension agent for specific recommendations.

Integrated Management in Riparian Sites

Preparing for Herbicide Application

Hand-pull 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.


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