The Effects of Detergent on Grass
Detergents have been used in the home lawn for many years as a homemade remedy against weeds and insects. Detergents can kill turf grass but they are an effective method of controlling certain pests. Used with care, detergents will make your grass vigorous by killing off competitors which could otherwise take necessary nutrients from the lawn.
Detergents such as liquid washing detergent are often used in the control of insects. Soap penetrates the cells of the insects' skin, says certified master gardener Mona Bawgus at PressofAtlanticCity.com, causing dehydration and death of the insects. The more effective the detergent in killing insects, the harsher it is on the grass. Horticultural insecticide soap is available that is less harmful to grass turf, causing less burning and brown foliage than normal detergent. Check the sensitivity of your plant to soap spray before application, since some varieties are sensitive.
Do not use detergents for extended periods in the lawn. Several sprays to kill insects may be necessary, but prolonged use of an insecticidal detergent will cause buildup in the soil. Since detergents are poisonous to plants, buildup may cause weakening in the plant roots. Heavy detergents may prevent the movement of water through the soil, mixing with it and causing it to bubble. This will cause dehydration of the turf. Detergents may remove nutrients from the soil as well.
Detergents such as borax are used in the control of some weeds like creeping charlie. When used in a moderate amount, borax will kill creeping charlie and only mildly damage grass that it comes in contact with. Too much borax, however, may kill entire areas of the turf. Hot, dry conditions during application may produce more damage in the turf grass. Cool, wet conditions at application will reduce injury. Apply 10 to 20 ounces of borax diluted into 2.5 gallons of water per 1,000 square feet of lawn.