Magazine - Professional Turf Diaries With Jerry. Pt. 7

By Jerry Spencer in Consultancy on 15th Apr 2008 6:00

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.

Effects of ethofumesate on seed germination.
For maximum turfgrass safety with herbicides, it is important to know the response of treatments on germinations of turfgrass seed. There are instances when ethofumesate will be applied for Poa annua to a couch green or fairway just after overseeding with perennial ryegrass or to fairways seeded to cool-season grasses following a renovation program.

Perennial ryegrass.
In Mississippi, greenhouse studies on the effects of ethofumesate applied to seed of several turfgrasses at seeding (PRE), one-half at seeding (PRE) plus one-half at 2 weeks after seeding (POST). Stand rating at 40 days after seeding shown that ethofumesate at 1.12 kg/Ha reduced stand of Pennfine perennial ryegrass 31% when applied as PRE. Stand reduction was 40% when ethofumesate was applied at 0.56 kg/Ha as PRE and 0.56 kg/Ha as POST. The perennial ryegrass stand decrease significantly as ethofumesate rates increased from 1.12 kg/Ha to 4.5 kg/Ha.

The stand reduction of 14 other perennial ryegrass cultivars in Mississippi was 41% when ethofumesate was applied PRE at 1.12 kg/Ha; 33% when 0.56 kg/Ha was applied as PRE and 0.56 kg/Ha applied as POST; and 24% when 1.12kg/Ha was applied as POST.
In the same Mississippi study, stand of Italian ryegrass was reduced 36% at 40 days when treated with ethofumesate as PRE at 1.12 kg/Ha and reduced 32% when treated as PRE at 0.56 kg/Ha and 0.56 kg/Ha as POST. Ethofumesate applied as POST at 1.12 kg/Ha had no affect on Italian ryegrass stand.
In a greenhouse study in Oregon, ethofumesate applied at 1.12 kg/Ha at planting did not affect the stand of perennial ryegrass at 7 weeks. During this period the stand was reduced 20% when treated at 2.24 kg/Ha and 38% when treated at 4.5 kg/Ha. The stand of Italian ryegrass was reduced 20% with ethofumesate at 1.12 kg/Ha, and reduced > 63% at higher rates.
A different type study was conducted in a germination growth chamber in Ohio on the inhibition of cool-season turfgrass germination. A 50 seed sample was used in each method and germination was conducted 14 days after treatment. Ethofumesate was applied in a chemical solution (0, one-half, full, and double rates) to perennial ryegrass using three methods as follows:

Soaked blotter germination method.
This method consisted of placing 4.0 ml of ethofumesate solution on a blue blotter in a petri dish where dry seed samples were placed.

Imbibed germination method.
Seed samples in this method were imbibed in chemical solutions (same as above) for 3 hours and then placed onto a blotter soaked in 4.0 ml pure water.

Dipped germination method.
This method consisted of placing the seed samples on a cheese cloth and spraying with the different chemical solutions and placing the samples on a dry germination paper and dried for 24 hours at room temperature. Samples were then placed on blue blotters soaked in pure water.

The germination with ethofumesate was 89% for soaked, 94% for imbibed, and 90% for the dipped method. For comparisons, the germination of perennial ryegrass treated with flurprimidol (Cutless) was > 91%, while the germination with trinexapac-ethyl was 70% for the soaked germination method and > 92% for the other germination methods.

Bentgrass.
In the greenhouse study conducted in Mississippi (see perennial ryegrass) ethofumesate applied as POST at 2 weeks after planting reduced stand of Highland colonial bentgrass only 26% at 40 days, but reduced shoot dry weight 97%. The results were similar for either Penncross, Emerald, and Penneagle creeping bentgrass.

In the growth chamber study in Ohio (see perennial ryegrass), creeping bentgrass germination ranged from 1 to 13% using the soaked and imbibed germination methods to 93% using the dipped germination method.

Kentucky bluegrass.
In the greenhouse study in Mississippi (see perennial ryegrass), ethofumesate applied as PRE at 1.12 kg/Ha or 0.56 kg/Ha applied as PRE and repeated as POST 2 weeks later reduced the stand of Adelphi Kentucky bluegrass < 15%. When the herbicide was applied as POST at 1.12 kg/Ha stands of Adelphi and Touchdown were not affected while the stand of Glade was reduced 24%, Flying was reduced 46% and Baron and Nugget were reduced > 50%.

Tall fescue.
The stand of tall fescue in Oregon was severely reduced at 7 weeks after planting in a greenhouse study when ethofumesate were applied at > 1.12 kg/Ha at time of planting. The stand was reduced 37% when treated at 1.12 kg/Ha and 88% when treated at 2.24 kg/Ha.

Poa annua biotypes.
Ethofumesate was evaluated on 15 different biotype of Poa annua in the greenhouse. All biotypes were treated twice with ethofumesate at 0.84kg/Ha as:
PRE + 28 days after planting (DAP)
28 + 56 DAP
56 + 84 DAP

In the PRE + 28 DAP treatment stand thinning was 95 to 100% for all except one biotype (51%).

In the 28 + 56 DAP treatment, control of the biotypes least susceptible to the PRE + 28 DAP was 53%. The control of other biotypes ranged from 84 to 100%.

In the 56 to 84 DAP treatment, only 2 biotypes were effectively controlled with ethofumesate while the control of the others ranged from 13 to 65%.

These results suggest that different Poa annua biotypes will perform differently to ethofumesate treatments. Note that the PRE + 28 DAP was the best timing for ethofumesate treatments. However, one biotype was not controlled from these treatments The non-controlled biotype could be resistant to ethofumesate. Also, note that the 56 and 84 DAP ethofumesate treatments controlled the least number of biotypes. However, the 2 biotypes that were controlled at these dates suggest that these biotypes were easier to control with ethofumesate than the other 13 biotypes. Poa annua would be much easier to control with ethofumesate if all Poa annua in the United States were these 2 biotypes.

Summary of seed germination treated with ethofumesate.
The safety of any herbicide is usually not as good on turfgrasses when evaluated in greenhouses and growth chambers than when evaluated under field conditions. These researchers indicate that in most instances when ethofumesate is applied closer to day of seeding in greenhouses and growth chambers, the expected turfgrass injury will probable be higher than when treatments are delayed until normal growth has occurred.

Even though ethofumesate has activity on several weeds, it appears from this review that the herbicide is best adapted for Poa annua control in cool-season grasses. The review shows some variation in Poa annua, but the biggest concern is turfgrass safety.

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