Home / Crops / Lessons from Ohio’s 2014 Fall Soybean Weed Survey

Lessons from Ohio’s 2014 Fall Soybean Weed Survey

The good news in the results of the 2014 Fall Soybean Weed Survey is that we have several areas of the state where growers are managing their resistant weed problems. I make the assumption that most of Ohio soybeans are RoundupReady, and that if weeds are still in the soybean field at the end of the season, then there must have been a failure of the system. This is not always correct, but then we are making assumptions that may not be too far off.

So who does the Fall Soybean Weed Survey by driving 80 miles on the road in each county? In Table 1, is a listing of the counties in the survey, the Extension educator, the number of fields and acres they checked.

Table 1. County, educator, acres and field number by county in the 2014 Fall Soybean Weed Survey.

CountyOSU Extension AgNR educator

Acres surveyed

Total number fields

ChampaignAmanda Douridas

3651

83

DarkeSam Custer

2783

95

DefianceBruce Clevenger

7085

104

FayetteAdam Shepard

4830

80

FultonEric Richer

6355

100

Geauga, Ashtabula, TrumbullLes Ober

2600

79

GreeneMary Griffith

6050

80

HardinMark Badertscher

3360

100

MarionSteve Prochaska

3210

61

MercerDennis Riethman

4270

99

MontgomerySuzanne Mills-Wasniak

5605

64

PauldingSarah Noggle

4062

72

ShelbyDebbie Brown

3430

101

UnionAmanda Douridas

4265

81

WilliamsFlo Chirra

5868

120

 

That is some 1,300 soybean fields and 67,000 acres they sampled to make the observations. Table 2 shows the number of clean fields in the survey area.

 

Table 2, counties and percent of clean fields ranked by the highest percent.

County

% Fields with no weeds evident

Williams

56%

Marion

52%

Defiance

52%

Mercer

52%

Darke

43%

Paulding

43%

Geauga, Ashtabula, Trumbull

42%

Hardin

41%

Fulton

35%

Montgomery

34%

Union

27%

Greene

10%

Champaign

10%

Fayette

9%

Shelby

5%

 

So we do have four counties with more than 50% of the soybean fields weed free. I’ll admit to a little surprise but also relief to know that we can manage the weed problems that have risen in the state. I also need to point out a couple of other items in Table 2. The three to four counties at the bottom were also near the bottom last year, meaning they may not have learned yet how to manage the problem. Also in Table 2, in the middle of the pack is the northeast Ohio area of Geauga, Ashtabula and Trumbull counties. We have been watching them for a while thanks to Les Ober’s efforts and see increasingly that marestail has moved into the western areas of that region.

So what weeds showed up this year in our surveys? We found the usual suspects that we have seen over the past several years. We also added pigweed to our list to check this year as we hear more and more remarks that this and related species are showing up in Ohio. We expected more finds of Palmer amaranth to show up, but when we looked on our random jaunts across the county, we did not see that. Table 3 shows low levels of pigweeds across the state.

 

Table 3. Pigweed incidence by county in percent in the 2014 Fall Soybean Weed Survey.

County% fields with Pigweed species
Champaign

0%

Darke

2%

Defiance

0%

Fayette

1%

Fulton

0%

Geauga, Ashtabula, Trumbull

0%

Greene

1%

Hardin

0%

Marion

0%

Mercer

14%

Montgomery

8%

Paulding

7%

Shelby

6%

Union

6%

Williams

18%

 

Several of the Extension educators noted that the pigweed species was tall waterhemp, which this may be spreading. For the most part as I said though, these are low numbers. Weed science graduate students are out checking some of these fields this fall and will be running resistance screens on the collected samples this winter. Two counties may have a problem — Mercer and Williams — the counties are not near each other but both sit on the Indiana border where there have been higher incidents of pigweed escapes.

 

Table 4 includes the rest of the weeds we saw this year across the state.

County

Total number fields

% fields with Marestail

% fields with Giant Ragweed

% fields with Volunteer corn

% fields with Common Ragweed

% fields with Lambs quarter

Greene

80

85%

29%

25%

1%

1%

Champaign

83

66%

18%

45%

5%

1%

Shelby

101

62%

63%

44%

5%

8%

Montgomery

64

58%

41%

30%

19%

9%

Fayette

80

49%

64%

31%

0%

0%

Union

81

46%

27%

28%

1%

1%

Fulton

100

42%

28%

7%

4%

5%

Marion

61

41%

18%

0%

0%

0%

Darke

95

33%

12%

16%

2%

4%

Hardin

100

32%

24%

13%

0%

0%

Defiance

104

31%

12%

4%

16%

8%

Williams

120

26%

0%

3%

0%

0%

Geauga, Ashtabula, Trumbull

79

22%

1%

15%

6%

16%

Paulding

72

19%

7%

7%

33%

4%

Mercer

99

14%

9%

15%

9%

0%

 

This table shows the county ranking by the level of marestail as a percent of fields with the weed. Giant ragweed also looks pretty bad this year. I work a lot in west central Ohio, and thought all year that giant would outdo marestail for the No. 1 spot. And why, oh why do we have volunteer corn? Ask your neighbors how to control this one. Lambsquarter problems are down this year, so this at least shows me we are using pre-emergent herbicides. Maybe it is the burndown where we are slipping.

 

What works?

As I toured Ohio soybean growing areas over the summer, I checked with growers on what worked well for them. They reported the efforts they have gone to that reduced their weed problems in soybeans. One young lady was so proud of her spotlessly clean fields; she had made the decision to go all LibertyLink.

This is the list that works, and it sounds an awful lot like the recommendations of Mark Loux our State Weed Management Specialist.

  1. Apply a fall burndown that includes 2,4-D
  2. Increased use of metribuzin
  3. A switch to LibertyLink varieties, or due diligence on these other suggestions
  4. Use of full rate of pre-emergent herbicide at planting in the spring

And the one thing I have learned through about three waves of new herbicide programs and developing weed resistance is that is until the disaster happens, everyone thinks it won’t happen to them. I know some have seen the recent approval of the 2,4-D resistant soybean from Dow, and likely soon to follow is the dicamba bean from Monsanto, but we know better than to go down that badly paved road again right? It seems the EPA has added some extra requirements to the Enlist label. One is that you will be watched and if you do not follow good weed management programs then the product will be pulled off the market. So, as we get our corn harvested this fall, take time to make that fall burndown application to take that first step in getting the problem solved in 2015.

Check Also

Weed answers for 2020 start this fall

By Harold Watters, CCA, Ohio State University Extension So this year I am getting even …

Leave a Reply

Your email address will not be published. Required fields are marked *