Preventing PL from infesting new sites is the easiest control. Be sure local gardens have no illegal PL plantings that produce seed. Monitor your sites (annually) and remove any small colonies or new young plants. Especially check areas near moving water, wetland/upland edges, storm sewer outlets or gardens that may have contained PL. One mature PL plant produces over 2 million seeds a season, so learn to recognize pre-flowering plants or search when PL just starts to bloom. Destroy them before they mature, flower and drop seeds, which can start before flowering ends. Dispose of plants in a capped landfill, or dry and burn them. Composting will not kill the seeds. Keep clothing and equipment seed-free to prevent its spread. Take responsibility to remove new plants wherever you see them. (Get landowner permission first.)

MECHANICAL CONTROL includes cutting, pulling or digging and drowning. Cutting is best done just before plants begin flowering. Cutting too early encourages more flower stems to grow than before. If done too late, seed may have already fallen. Since lower pods can drop seed while upper flowers are still blooming, check for seed. If none, simply bag all cuttings (to prevent them from rooting). If there is seed, cut off each top while carefully holding it upright, then bend it over into a bag to catch any dropping seeds. Watch for holes in your bags so you don't spread seed where you drag the bags. Dispose of plant parts as above. Always back away from sprayed areas as you go to prevent getting herbicide on your clothes.

Pulling and digging can be effective, but can also be disruptive by creating disturbed bare spots, which are good sites for PL seeds to germinate, or leaving behind root fragments that grow into new plants. Use these methods primarily with small plants in loose soils, since they do not usually leave behind large gaps, nor root tips. Large plants with multiple stems and brittle roots often do. Dispose of plants as above. Drowning young PL is effective if plants are completely submerged for a year (often after being cut to decrease height.)

CHEMICAL CONTROL

This is usually the best way to eliminate PL quickly, especially with mature plants. Chemicals used have a short soil life. Timing is important: Treat in late July or August, but before flowering to prevent seed set.

The best method is to cut stems and paint the base cuts with herbicide. Cut low on the stem (about knee level) with one hand and apply the herbicide with a second hand, while carefully stuffing the plant top into a plastic bag with the third and fourth hands (a two person crew works well for this). The herbicide can be applied with a small drip bottle or spray bottle, which can be adjusted to release only a small amount. Try to cover the entire cut portion of the stem, but not let the herbicide drip onto other plants since it is non-selective and can kill any plant it touches. Glyphosate herbicides Roundup and Glyfos are typically used, but if it is very wet in the area use Rodeo, a glyphosate formulated for use over water. Stem applied herbicides should be mixed to 20 to 40% active ingredient. Since you must treat at least some stems of each plant and they often grow together in a clump, all stems in the clump should be treated to be sure all plants are treated. Bag all cuttings since they can root if they come in contact with water or moist soil and dispose of as above.

Another method is using very carefully targeted foliar applications of herbicide (NOT broadcast spraying). This may reduce costs for sites with very high densities of PL, since the work should be easier and there will be fewer other plant species to hit accidentally. Use a glyphosate formulated for use around water. A weaker solution of around 1% active ingredient can be used and it is generally necessary to wet only 25% of the foliage to kill the plant. Triclopyr (Garlon 3A) is another herbicide that can be used as a foliar spray. It is formulated for use around water and does not harm grasses or sedges. Unfortunately, it has not received final approval from the EPA for wetlands. Wet most of the foliage if using this chemical.

You must obtain a permit from WDNR before applying any chemical over standing water. The process has been streamlined for control of purple loosestrife and there is no cost. The appropriate person to contact is your regional WDNR Aquatic Plant Management Coordinator (list available from bio-control program). S/he will want to know about your site and plan, may make further suggestions and will issue your permit.

Chemicals, Tools, and Costs – Chemicals and tools to apply them are often available from local farm cooperative stores and garden shops. Your APM Coordinator may be able to help you locate a supplier near-by. If you cannot get the herbicides locally, a business in DeForest, Wisconsin will ship them. Contact them by calling 800/362-8049.

Roundup is for drier sites and costs about $90/gallon. Buying in volume will save you money: 2.5 gallons of Roundup costs about $110! It requires no additives. Rodeo is for very wet sites and costs around $120/gallon. It must be mixed with a nonionic surfactant, about $18/gallon. Monsanto (800/332-3111) manufactures both of these glyphosates. Glyfos is a generic version of Roundup made by Cheminova (800/548-6113); if interested call them for a local supplier. Glyfos AQ is the equivalent to Rodeo, but is not yet generally available. Concentrations discussed above are approximate since requirements are variable on different populations of plants in different situations. Test yours to be sure you use an appropriate amount of active ingredient. Call manufacturers or your APM Coordinator if you have additional questions.