Cultural Practices for Improved Weed Management

Any cultural practice that increases the density and vigor of desirable turfgrasses will discourage competition from weeds. Weeds can only exist if there is space for them. Thus, cultural practices for weed control in turf are aimed at shading and crowding the young weed seedlings by producing a dense sod. Effective cultural control measures include the proper selection and establishment of turfgrasses, adequate liming and fertilization, proper mowing practices, judicious watering, and insect and disease control.

Turfgrasses that are not adapted to the environmental conditions and intended use of the turf may become weak, resulting in a thin stand. When there are voids in the turf, weeds have an opportunity to grow and compete with the desirable species. The use of proper establishment procedures helps to ensure that a dense turf will compete with germinating weed seedlings.

Too high or too low a soil pH and inadequate fertilization lessens the competitiveness of turfgrasses, resulting in reduced density and subsequent weed invasion. Soil testing is the key to proper pH management and fertilization. Soil test recommendations provide guidelines for fertilization and liming to establish and maintain turfgrasses. Adequate nitrogen should be supplied to favor the desirable species in the stand. Phosphorus fertilization increases seedling vigor and is one factor in reducing weed infestations in newly established turf. Lime should be applied when the soil is too acid, and acidifying materials can be used when the pH is too high.

Improper mowing is one of the most common causes of weed invasion. Mowing heights that are too short result in weakened turfgrasses and weed encroachment. Most lawns should be cut at least 2 inches or higher.

Improper watering also contributes to weed invasion. Frequent light watering encourages shallow rooting and promotes weak turf, which becomes susceptible to insect and disease attacks as well as damage from traffic. Frequent light watering also encourages germination and development of weeds at the expense of turfgrasses. Watering deeply (4 to 6 inches) before turfgrasses show signs of wilting is a practical approach to a sound watering program. A soil probe can be used to monitor soil moisture levels.

Most weeds are opportunistic, filling in voids in turf caused by diseases and insects. Diseases can be controlled by cultural practices and with fungicides. Insect damage can be reduced by maintaining a healthy turf, by using insecticides, and by using biorational means of control, such as endophyte-containing ryegrasses and fescues, which discourage leaf and stem-feeding insects.