Marestail. Photo by OSU Extension.

Fall weed survey: We still have a problem

Almost every year since 2006, the OSU Extension Agriculture and Natural Resource county-based educators have been conducting fall soybean weed surveys. Our concern is that resistant weeds may be increasing and we want to be a little ahead of the curve so we can tell you our readers. Table 1 shows our results summary across those years. Missing is 2007. I was the only person conducting a survey that year and 2012 is also missing, which is the only year I have missed.

 

Table 1. Weed survey summary – 2006 to 2013 with the average % of fields infested at any level.

Weed below,   year >200620082009201020112013
Weedfree372525313034
Giant ragweed422521262631
Common ragweed9 22710106
Lambsquarters151217974
Marestail193839324039
Volunteer corn3721221023

 

The top five weeds we see each year are those noted above, for 2013 we did add Giant foxtail because so many of our educators (10 of 14) named that as the next most noted weed. We also asked the group to watch for “Pigweed” because we are concerned about Palmer amaranth and Tall waterhemp making greater inroads in the state. Generally weed numbers remained about the same as they have for a number of years.

Table 2 shows the counties surveyed, the person conducting the survey, the number of fields, an estimate of the acres viewed and the percent of fields with no weeds.

CountyEducator/surveyor

# fields

Acres est.

No weeds
AuglaizeJohn Smith

80

3665

25%

ChampaignHarold Watters

80

4622

23%

DarkeSam Custer

78

2126

38%

DefianceBruce Clevenger

120

6480

55%

FayetteAdam Shepard

96

7027

2%

FultonEric Richer

106

6085

40%

GeAshTrumLes Ober

120

2518

79%

HancockEd Lentz

120

5735

18%

HardinMark Badertscher

105

4539

34%

Marion/WyandotSteve Prochaska

48

2300

44%

MercerGlen Arnold

103

no est.

43%

MontgomerySuzanne Mills-Wasniak

65

5985

40%

ShelbyDebbie Brown

81

3145

10%

UnionAmanda Douridas

84

3762

21%

average >

92

4461

34%

Our goal was to see 80 fields in each county; we averaged 92. It is good that we did have 34% of our fields with no weeds noted but it wasn’t that long ago that there would be no weeds in any field. It is also interesting to note that some counties have less that 20% of their fields weed free — Fayette with only 2%, Shelby with 10%, Hancock with 18% and Union and Champaign close with 21 and 23%.

 

Table 3. 2013 Ohio Soybean Field Weed Survey results by Percent of Fields with an appearance of the particular weed.

County

Giant Ragweed

Common Ragweed

Lambs quarter

Mares   tail

Volunteer corn

Pigweed

Giant Foxtail

Auglaize

49%

8%

1%

50%

23%

0%

Champaign

36%

0%

5%

56%

18%

4%

Darke

19%

6%

5%

28%

31%

4%

4%

Defiance

9%

18%

0%

18%

7%

0%

3%

Fayette

76%

0%

0%

71%

34%

2%

2%

Fulton

27%

8%

8%

32%

14%

2%

2%

GeAshTrum

0%

6%

6%

11%

3%

4%

3%

Hancock

30%

13%

1%

52%

35%

12%

21%

Hardin

30%

0%

4%

27%

30%

4%

5%

Marion/Wyandot

33%

0%

0%

29%

0%

0%

Mercer

17%

1%

4%

39%

18%

17%

2%

Montgomery

23%

17%

11%

45%

23%

15%

Shelby

49%

7%

12%

49%

57%

7%

11%

Union

36%

1%

5%

38%

25%

4%

5%

Table 3 indicates the appearance of each weed, but may not indicate that we have a problem. We rate our fields as we conduct the survey on a scale of Zero to three. With a “0” indicating no weeds, a “1” indicates an occasional weed, perhaps just an occasional individual plant. A score of “2” is when we start getting concerned — this indicates large patches of 8 or more plants scattered in the field. The highest ranking, a “3”, indicates wide spread patches across the field. When we see a single species of weed in the field that is also a good indicator that we have a breakdown of the herbicide program.

 

Table 4. 2013 Ohio Soybean Field Weed Survey, percent of fields with Infestation Level score of a 2 or a 3.

 

County

Giant Ragweed

Common Ragweed

Lambs quarter

Marestail

Volunteer corn

Auglaize

14%

1%

0%

25%

5%

Champaign

8%

0%

1%

26%

0%

Darke

12%

4%

1%

18%

5%

Defiance

5%

12%

0%

8%

0%

Fayette

35%

0%

0%

39%

13%

Fulton

9%

2%

3%

17%

4%

GeAshTrum

0%

3%

1%

2%

0%

Hancock

7%

3%

0%

16%

4%

Hardin

7%

3%

0%

16%

4%

Marion/Wyandot

29%

0%

0%

23%

0%

Mercer

6%

1%

0%

10%

2%

Montgomery

11%

3%

3%

18%

12%

Shelby

19%

4%

6%

22%

10%

Union

13%

0%

0%

15%

1%

Table 4 shows the percent of fields with those higher scores. I added the percent of 2s and 3s together to show those numbers of fields where we have concerns about resistance development.

The first thing I see is that marestail is still a problem across the state. Giant ragweed is becoming a bigger problem and in some areas is as bad as the marestail. It is good to see that common ragweed, whose appearance across the state varies by soil type, is not so bad and this year. Lambsquarters, which was so bad in the dry year 2012, is pretty much under control again. Volunteer corn, assumed to be Roundup Ready, continues to be a problem in many fields.

 

How do we control our problem weeds?

  • Put more effort into herbicide selection.
  • Don’t assume that glyphosate works on all weeds anymore — it doesn’t. Even northeast Ohio now has some concern about resistant Marestail.
  • Apply an effective burndown in no-till soybeans — meaning not glyphosate alone but add 2,4-D, at the least.
  • Select and apply a pre-emergent herbicide product or two. Boost your metribuzin rates.
  • And apply an effective post herbicide to small weeds. In the case of volunteer corn add a post grass product, such as Select or Assure to the mix.

As we drive around the county to make these surveys it is very obvious that some producers are capable of doing a very good job of weed control. My guess is that yes they spend a few more dollars for their weed control, but they sleep easier at night and probably keep the landlady happy, too. And good management of weeds will keep resistance at bay.

Get educated on best management practices for weed control this winter. All counties in Ohio offer Pesticide Recertification programs in Ohio. Just because you don’t apply restricted use herbicides doesn’t mean you cannot learn a little about how to reduce your weed problems. This website can help find an education program for you: http://pested.osu.edu/privaterecert.html, or call the county Extension office. Another reason to start attending these information updates is because soon in Ohio any producer who applies fertilizer to more than 50 acres will likely be required to have a “Pesticide Applicators License,” for the nutrient application if nothing else.

Check Also

H2Ohio: Moving beyond Lake Erie

By Matt Reese H2Ohio is expanding beyond the Lake Erie Watershed. Late in 2021, Ohio …

Leave a Reply

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