Prevention
Prevention is the first line of defense and keeps weeds from occurring or increasing in an area. Preventive techniques include planting high quality, weed-seed-free crops or grass seed. Legislative items, such as clean-seed acts and weed-management laws, also can help stop weed problems before they occur or may deter weed spread. Controlling existing infestations so they do not increase in size also is an important preventive measure.
An important preventive measure related to control is to keep weeds from going to seed. This is important for annuals and biennials, because that is the only way they reproduce. Perennials reproduce from seed, as well as vegetatively from their root systems. Annual weeds live for one growing season, biennials for two and perennials more than two. However, preventing seed set is extremely important to keep perennials from starting new infestations some distance from existing ones.
Eradication
Eradication is the removal of weeds from an area so they will not recur unless reintroduced. If eradication creates an open area, one weed problem may be cured simply to create another one. If eradication is necessary, revegetate the ground to prevent another weed infestation. Eradication is desirable for small patches, 10 to 100 feet in diameter, but not always for larger ones.
Control
Control, the most common management strategy, reduces a weed population to a level where you can make a living off of or enjoy using the land. Adequate control also may prevent future infestations. There are four control methods: cultural, mechanical, biological and chemical.
Cultural control methods promote growth of desirable plants. Seeding is the most commonly used cultural control method and must be combined with control methods that decrease the target weed population and gives the seeded species an opening in the environment to successfully germinate and establish (colonize). The USDA-Natural Resource Conservation Service is an outstanding source of information as to what species to plant in a particular area and at what rate. Fertilization, irrigation and planting at optimum densities let crops compete with weeds and not with each other. While nitrogen fertilization increases yields in grass hay meadows, it also fosters weed establishment and growth. Fertilize cautiously, especially with nitrogen, and only when necessary as determined by soil testing.