Cover Feature: Want To Save Money?

The introduction of Roundup Ready sugarbeets will arguably be remembered as the most significant change in sugarbeet production since the commercial introduction of monogerm beet seed in 1956.

For everyone who grew conventional beets before Roundup Ready beets came along, weed control in Roundup Ready beets is a breeze compared to conventional beets.

It used to be unusual to see numerous sugarbeet fields nearly weed free. A common lambsquarters plant here and a pigweed there mixed in with some kochia, hairy nightshade, and barnyardgrass used to be the norm as you looked across many beet fields in August.

Now it's just the opposite-nearly all of the sugarbeet fields are clean of weeds.
Aside from some weeds encroaching along the field borders or sometimes in the wheel tracks of the sprayer that kicked up dust and tied up the glyphosate before it could get into the plants, sugarbeet fields are clean.



RESISTANCE ATTENTION


Roundup Ready sugarbeets are definitely a boon to the beet farmer; just like the technology has changed the lives of many corn, soybean and cotton farmers in the Midwest and southern U.S.

Unlike the Midwest and southern farmers who adopted Roundup Ready crops at a slower, but steady pace, Idaho and Oregon beet growers have adopted the Roundup Ready technology at an amazing rate.

Nearly all of the beets grown in these two states are Roundup Ready. This is good news to Monsanto and to the growers, but to weed scientists, this is cause for some concern.
The concern is the development of glyphosate resistant weeds.



DISCUSSING BIOTYPES


Since the discovery of the first glyphosate resistant weed, which was horseweed (Conyza canadensis), 10 years ago in Delaware, there are now biotypes of 10 weed species identified as resistant to glyphosate.
A biotype is a strain or sub-group of a species. Glyphosate resistant weeds have been reported in 22 states, including Oregon and California. None have yet been reported in Idaho.

Kochia is the most recent weed to become resistant to glyphosate. In a recently reported study from Kansas State University, three glyphosate resistant kochia biotypes have been identified.

The K-State study evaluated several kochia biotypes including three from Idaho, two from Washington, and five from Kansas.
The three biotypes from Idaho came from Jerome and Minidoka counties. Fortunately, none of these biotypes nor the ones from Washington showed any tolerance to glyphosate.

In our weed control studies in Idaho and Oregon, kochia has been effectively controlled with glyphosate.
However, it is important not to get complacent because kochia has shown the ability to develop resistant biotypes to many other herbicides. It would be unwise to think we could never have problems with glyphosate resistant weeds in Idaho or Oregon.



TANK MIXING


Since we first began looking at tank mixing other herbicides with glyphosate as a means of reducing the potential for glyphosate resistant weeds, we have found that most of the registered postemergence sugarbeet herbicides did not provide any additional help in controlling weeds with glyphosate.

That's not to say none of them would be of value in preventing glyphosate resistant weeds from developing; it's just that they did not make glyphosate any more effective or economical to use.
One big exception to this is tank mixing Stinger to get better Canada thistle control.

We have found that tank mixing registered soil-active herbicides with glyphosate can improve weed control and save money at the same time.
We have made recommendations to growers to consider using glyphosate in combination with soil-active herbicides such as Outlook, Nortron, Dual Magnum, Eptam, and RoNeet. One of the most common responses has been that it is not economical and because it is much easier to just use glyphosate.



GLYPHOSATE ALONE


We decided to look more closely at the economics of using glyphosate by itself compared to tank mixing a soil-active herbicide with glyphosate.
Studies were conducted at the University of Idaho Kimberly Research and Extension Center and the Oregon State University Malheur Experiment Station near Ontario.

Table 1 lists the herbicides and rates used, herbicide cost, number of applications and total cost, including the application cost each time herbicide was applied.

The cost estimates were based on survey data collected by University of Idaho agricultural economists1.



ROUNDUP POWERMAX


At Kimberly, the weed population included common lambsquarters, kochia, redroot pigweed, annual sowthistle, common mallow, green foxtail and barnyardgrass (Table 2).

Weed control at Kimberly was very good early in the growing season with most of the treatments, including the single applications, such as Roundup PowerMax (RPM) alone and RPM tank mixed with another herbicide.
By harvest time however, multiple RPM applications alone or applied with a tank-mix partner was generally better than a single application. One of the reasons for this is attributed to not controlling later weed emergence, particularly where there was an opening between beets within or between rows.

Three RPM applications were needed for season-long control of most of the weed species compared to one or two. RPM + Nortron applied at the two-leaf stage followed by (fb) RPM alone at the six-leaf stage was equal to RPM applied three times for the best overall weed control.
Many of the other herbicide treatments did not provide the late-season weed control, although many of the weedy escapes were small and non-competitive.



MALHEUR EXPERIMENT STATION


The main weeds at the Malheur Experiment Station near Ontario consisted of common lambsquarters, hairy nightshade, redroot pigweed and barnyardgrass (Table 3).

At this location, the beets were planted at a higher population and thinned to an eight-inch spacing to provide a uniform stand.
We believe this made a big difference in the weed control results with the same treatments that were used in Idaho.

RPM applied one time and a single RPM + Nortron application were the only two treatments that did not effectively control all weeds into mid-August.
Barnyardgrass with RPM alone dropped from 91 percent in June to 78 percent by August 11 and interestingly, RPM + Nortron control of barnyardgrass also dropped to 75 percent and hairy nightshade control dropped to 78 percent.

More importantly, weed control with all of the single applications of RPM + Outlook, Dual Magnum, Eptam or RoNeet ranged from 91 to 100 percent from the first evaluations in June to the later evaluation in August.
As a footnote to the weed control results with Eptam and RoNeet tank mixed with RPM at Ontario, the beets were furrow irrigated within three days after the herbicide applications, which helped to activate these products before they volatilized.



NET RETURN


Sugarbeet yields overall at Ontario were higher than at Kimberly, at least in part, due to the longer growing season at Ontario (Table 4).
However, the effect of weed competition at Kimberly had a greater impact on yield of those treatments that did not control weeds as well.

Consequently, we saw a greater difference in sugarbeet yield and net return among the different weed control treatments.
Among the highest yielding treatments were RPM alone applied three times, Nortron applied preemergence fb RPM, RPM fb RPM fb RPM + Nortron, RPM fb RPM + Dual Magnum, and RPM fb RPM + Eptam.

These same treatments were among those with the highest net return. At Ontario, 13 treatments ranked among the highest yielding treatments and nine of those were among the highest net returns.
RPM applied 2 or 3 times, RPM + Dual Magnum, RPM fb RPM fb RPM + Nortron, RPM fb RPM + Dual Magnum, and RPM fb RPM fb Eptam had the highest net returns.



WISE CONCLUSION


The bottom line is there are tank-mix partners that can be used with RPM or other glyphosate that will effectively and economically control weeds in Roundup Ready sugarbeets.

Roundup alone has been proven to effectively control weeds with multiple applications, but the addition of a tank mix partner will help prevent the development of glyphosate resistant weeds. Roundup Ready sugarbeets is a valuable technology and the wiser this technology is used, the longer it will be valuable.