Magazine - Professional Turf Diaries With Jerry. Pt. 4

By Jerry Spencer in Consultancy on 12th Mar 2008 5:50

In Jerry's diaries we will look at ethofumesate. Ethofumesate has been available for years but is seldom used as other ‘easier’ options are now available which are not always the best option.

Other Weed control.
The control of several weed species have been evaluated only once with ethofumesate. Therefore, the information given for these weeds are preliminary and results should be reviewed with this in mind.

Crowsfoot grass control.
Crowsfoot grass control was poor in Tennessee as the control with ethofumesate at 2.24 kg/Ha was 15% by 10 weeks after treatment. When treatments were repeated at 1.12 kilograms per hectare the following 3-years, crowsfoot grass control increased to only 59% which was unacceptable by the end of the fourth year.

Prostrate spurge.
Prostrate spurge control was poor in Rhode Island (33%) when ethofumesate was applied at 1.88 kg/Ha.

Dandelions and henbit control.
Ethofumesate applied at 4.5 kg/Ha in Maryland did not control any of the dandelions and only 29% of henbit.

White clover control.
White clover control in perennial ryegrass in Maryland was >90% early September when treated with ethofumesate at 2.24 kg/Ha in early June. There was no advantage in control from a 4.5 kg/Ha rate compared with the lower rate.

Summary of other weeds.
Ethofumesate had excellent activity on rattail fescue, white clover, and volunteer wheat, but not on crowsfoot grass, prostrate spurge, dandelions, and henbit.

Turfgrass Tolerance
When herbicides are applied to turfgrasses to control weeds, it is desirable that the herbicide not cause any injury to the turf. When injury occurs it is classified either as acceptable or unacceptable. The level of acceptable injury means that the turfgrass injury is temporary and the turf will recover within a short period. However, the level of acceptable injury may vary according to turfgrass species or where the grass is used. For example, an acceptable level of injury for a golf green is 10 to 15% compared to up to 30% on fairways and roughs. Acceptable injury will include leaf discoloration, but no stand loss. Unacceptable turfgrass injury means that the herbicide injured the turf too severely to be acceptable and generally caused a reduction in stand density.
The cool-season grasses that ethofumesate is primarily used for Poa annua control are perennial ryegrass, Kentucky bluegrass, and creeping bentgrass.

Perennial ryegrass tolerance.
When used as the main turfgrass. Perennial ryegrass is considered to be  the safest turfgrass to ethofumesate treatments. The descending order of tolerance from ethofumesate is:
perennial ryegrass
> tall fescue
> zoysiagrass = creeping bentgrass
> Kentucky bluegrass
> Poa annua

In a green-house study in Oregon, a stand of Italian ryegrass was reduced when ethofumesate was applied above 1.12 kg/Ha. Perennial ryegrass tolerated higher ethofumesate rates than Italian ryegrass. At 1.12 kg/Ha the stand of Italian ryegrass was 80% compared to 100% for perennial ryegrass. At 2.24 kg/Ha the stands were 37% for Italian ryegrass and 80% for perennial ryegrass. Even though the 4.5 kg/Ha rate reduced stand of Italian ryegrass, it did not adversely affect seed production. The germination of ryegrass seed harvested from ethofumesate treated plots at < 4.5 kg/Ha was not affected.

Read more articles in Consultancy, by Jerry Spencer or from March 2008.