WEED MANAGEMENT CONCEPTS: Developing Native Forb Seed Production

Strategies

Corey Ransom

Methods of Weed Control

• Preventative

• Biological

• Cultural

• Mechanical

• Chemical

Preventive Weed Control in Row Crops

• Clean equipment (planting, cultivating, harvest)

• Clean field borders

• Weed screens for irrigation water

• Prevention of weed seed production

• Spot treatment

Cultural Control

• Crop rotation

• Site selection

• Stale seedbed

• Seedbed preparation

• Proper planting date/depth/conditions/density

• Competitive varieties/disease resistant/vigor

• Disease and insect management

• Fertility management/placement

• Irrigation management – Drip?

Physical and Mechanical Control

• Preplant Tillage or Cultivation

• Preemergence Cultivation

• In Crop Cultivation

• Blind Cultivation

• Mulches

• Flaming (nonselective/selective)

• Handweeding

Opportunities to innovate

cultivation tools

Hand weeding intra-row weeds

Crop Hour/ha

Onion sown 100-400

Carrot sown 100-400

Sugarbeet sown 80-150

Transplants 20-50

Time consumption for hand weeding

DIAS

Chemical Weed Control

Few herbicides that could

currently be legally used to

control weeds in native forb

seed production.

We need to identify and label

herbicides that can be used

to selectively control weeds

in our forb seed crops.

Herbicide Selectivity

Definition

- a treatment that at a given dosage is toxic

to some plant species but does not

damage others.

Herbicide Selectivity

1. Timing of herbicide application relative to crop growth (Roundup while crop is dormant)

2. Herbicide placement relative to:- Pattern of crop growth and development

- Contact with plants (banding, drop nozzles)

Mechanisms (Physical):

Herbicide Selectivity Through

Placement/Timing

www.wyliesprayers.com

Selective Placement

Hooded band sprayer

- can shield spray or plant

- generally use herbicide that

is not systemic

Herbicide Selectivity

1. Differential absorption (includes retention)

2. Differential translocation.

3. Differential metabolism.

4. Differences in sensitivity at the target site.

Mechanisms (Physiological):

Herbicide Selectivity Due to Plant Physiology

Physiological – differences in plant growth

Herbicide Selectivity Due to Plant Physiology

Physiological – Differences in plant growth

Ex. Contact herbicides in perennial crops.

Objective – Herbicides for Seed Production

Identify herbicides for weed management in forb seed production.

- Basalt milkvetch

- Western prairie clover

- Searls’ prairie clover

- Tapertip hawksbeard

Initial Preemergence Herbicide Screen

-50 seeds per flat.

-50/50 Sandy Loam Soil with peat and vermiculite potting soil.

-sprayed in chamber at 20 gpa.

-Crepis stored at 34 F for 3 weeks.

-evaluated 4 weeks after treatment.

Species:

- Basalt milkvetch

- Western prairie clover

- Searls’ prairie clover

- Tapertip hawksbeard

Preemergence Herbicides and Rates

Kerb 1.0

Treflan 0.375

Prowl H2O 0.75

Outlook 0.656

Sencor 0.375

Plateau 0.0625

Olympus 0.0267

Chateau 0.047

Tapertip Hawksbeard SymptomsSencor Treflan

Olympus Prowl H2O Plateau

Kerb

Untreated

Basalt Milkvetch Symptoms

Sencor

TreflanOlympusProwl H2O

Kerb

Outlook

Western Prairie Clover SymptomsTreflan

Olympus

Prowl H2O Outlook

Untreated

Postemergence Herbicide Screening, 2009

Conducted on fields established in 2005 as transplants from cone-tainers.

Plants were spaced 0.5 m.

Herbicide treatments applied May 12, 15, and 21, 2009.

Applications made with a shielded bicycle sprayer at 20 gpa and 30 psi.

Multiple accessions and inconsistent plant vigor prior to treatment add to variability in these trials.

Herbicide Treatments on Basalt Milkvetch

• Application made May 15.

• Injury evaluated May 26 (11 DAT) and June 23 (41 DAT).

• Biomass taken July 23.

Herbicide Rates

lb ai/A product

Buctril 0.25 1.0 pt

2,4-DB 0.25 1.0 pt

Transline 0.124 0.33 pt

Paramount + MSO 0.248 0.33 lb

Raptor + MSO 0.078 10.0 oz

MSO at 1.0% v/v

Basalt Milkvetch Injury on May 23 and June 25

• Transline again caused significant season long injury

• 2,4-DB , Paramount, and Raptor had among the least injury

Treatment

Buctril 2,4-DB Transline Paramount Raptor

Inju

ry (

%)

0

10

20

30

40

50

60

70

11 DAT

41 DAT

Milkvetch Plant Weight in Response to Herbicides

• Buctril and Transline significantly reduced plant biomass.

Treatment

Untreated Buctril 2,4-DB Transline Paramount Raptor

Bio

ma

ss

(g

/pla

nt)

0

5

10

15

20

25

a

a

b

aa

b

Millkvetch Flowering in Response to Herbicides

Treatment

Untreated Buctril 2,4-DB Transline Paramount Raptor

Flo

weri

ng

(p

lan

ts/p

lot)

0

2

4

6

8

10

12

a

ab

bc bc

bc

c

Herbicide Injury in Basalt Milkvetch

Herbicide Treatments on Western Prairie Clover

• Applied May 21.

• Injury evaluated May 26 (5 DAT) and June 25 (35 DAT).

• Plant biomass and seed head biomass August 6.

Herbicide Rates

lb ai/A product

Prowl H2O 0.71 1.5 pt

Outlook 0.84 18.0 oz

Goal 0.25 0.66 lb

Chateau + NIS 0.064 1.0 pt

Sencor + NIS 0.5 0.66 lb

Buctril 0.25 1.0 pt

2,4-DB 0.25 1.0 pt

Transline 0.124 0.33 pt

Paramount + MSO 0.248 0.33 lb

Raptor + MSO 0.078 10.0 oz

Milestone 0.047 3.0 oz

NIS at 0.25% v/v

MSO at 1.0% v/v

Western Prairie Clover Response to HerbicidesInjury Biomass

Herbicide 5 DAT 35 DAT Veg. Seed head

----------------%-------------- ----------g/plot----------

Untreated - - 520 243

Prowl H2O 10 1 545 203

Outlook 6 4 616 189

Goal 64 26 513 218

Chateau + NIS 56 18 479 203

Sencor + NIS 21 5 571 140

Buctril 13 14 337 126

2,4-DB 23 10 393 150

Transline 41 44 416 32

Paramount + MSO 25 10 704 191

Raptor + MSO 38 18 446 185

Milestone 35 63 257 2

Herbicide Injury in Prairie Clover

Impact of Application Timing

• No herbicide injury was evident in 2008 when applications were made while prairie clover was dormant.

• Significant injury appeared when actively growing prairie clover was treated in 2009.

Issue of crop selectivity vs. weed efficacy.

Conclusions – Seed Production

1. 2,4-DB warrants further investigation for postemergence use in basalt milkvetch.

2. Established western and Searls’ prairie clover appear to tolerate postemergence treatments of several herbicides, but impact on seed yield and viability has not been determined.

3. Transline and Milestone is too injurious for potential use.

4. Likely, the use of soil active herbicides will continue to cause minimal damage to established plants.

Herbicides That Could Have Great Utility

1. Graminicides – Poast, Select, etc.

2. Preemergence herbicides used in established plantings - Prowl, Outlook

3. Preemergence soil active herbicides for establishment?

4. Postemergence herbicides – Contact and Non-selective

5. Postemergence herbicides – Selective

Where Do We Go From Here?

1. Small acreage high value crops

2. Require “Third Party” indemnification label

3. Who will hold the label?

Need to have herbicides registered for use in native seed crops.

USDI BLM Great Basin Restoration Initiative, GBNPSIP, and

USDA FS Rocky Mountain Research Station