The phytotoxicity of selected herbicides and their residual effects in the establishment of emerald zoysia

Desirable herbicides for aiding the establishment of turfgrasses are those which provide a high level of weed control and are non phytotoxic to the newly planted turfgrass.

Many researchers have reported on the foliage symptoms of herbicidal injury to established turfgrasses. Some workers have studied the effects of herbicides on newly seeded turfgrasses. However, very little work has been conducted to determine the effects of herbicides on vegetatively propagated turfgrasses at the time of their establishment.

Extensive research has shown that most of the more commonly used preemergence type herbicides will provide excellent weed control in established turfgrasses if applied properly and at the correct rate. However, many of these same herbicides have caused considerable turfgrass injury.

Prior to the use of a preemergence herbicide it is desirable to know the residual life of the chemical for its safe and efficient use. However, information concerning the residual activity of many of these herbicides is quite limited.

In the spring of I965, a 2 year study was started at Knoxville, Tennessee to investigate (1) the effectiveness of several preemergence type herbicides in controlling certain weeds, (2) the tolerance of newly plugged 'Emerald' zoysia (Zoysia japonica x Z. tenuifolia Willd, ex Trin.) to these herbicides, (3) the effects of fresh herbicide treatments and soil herbicide residues on the root regrowth of common Kentucky bluegrass (Poa pratensis L.) sod plugs grown under greenhouse conditions, and (4) the rate of dissipation or depth of penetration of the herbicides which were applied to the zoysia plots in the field.