Challenges in future weed management

Bärbel Gerowitt University of Rostock Faculty of Agricultural and Environmental Sciences– Crop Health

SLU växtskyddskonferens Uppsala 14. November 2018

3Photos: H-H Steinmann

4Photo: H-H Steinmann

Current Glyphosate Debate in Germany

http://www.bund.net/aktiv_werden/aktionen/glyphosat_verbieten/

• Use of glyphosate and target species

Glyphosate Use in German Arable Farming 2014 (Inventory of 2014/15, 2026 Farmers)

Overall application area: 37 % of AA in GER

Pre-harvest: 2,2 % of arable area (AA)

Post-harvest (Stubble): 22 % of arable area

Pre-seeding: 13 % of arable area

Wiese et al. 2017

0

1000

2000

3000

4000

5000

6000

7000

8000

1992 1996 2000 2004 2008 2012

Glyphosate sales in Germany (BVL, DESTATIS)

t/a a.i.

Andert, Bürger, Mutz, Gerowitt, E. J Agr. 2018

WB=1.117, WW=1.820, SB=427, MA= 2.013, WOR=1.436 fields

Glyphosat (GBH) pre-crop and selective herbicides in crop

Andert, Bürger, Mutz, Gerowitt, E. J Agr. 2018

Winter wheat

Mais

Koning, de Mol, Gerowitt, Soil Till Res. 2019

Glyphosate

Public discussion on glyphosate and human health

Amounts used are crucial

Replace glyphosate in arable systems

Soil cultivation systems will change

Future challenges are more fundamental

12

Current Glyphosate Debate in Germany

http://www.bund.net/aktiv_werden/aktionen/glyphosat_verbieten/

Herbicide resistance?

Weeds are changing

Source: Heap 2016

0

5

10

15

20

25

30

35

1955 1975 1995 2015

Species with herbicide-resistent biotypes in GermanyNo.

Weeds are changing

Source: Meyer et al. 2014

0

5

10

15

20

25

30

35

1955 1975 1995 2015

Mean species on arable fields

Species no.

Conversation aspect

Red lists document losses in individuals and species

Many arable weed species are affected, approx. 1/3, increasing trend

Historically rare and frequent species are concerned

Vitamin C(mg/100 g f.w.)

Weeds VegetablesSonchus oleraceus 210Urtica urens 202 Broccoli 95Papaver rhoeas 200 Spinach 54Mercurialis annua 192 Celery 32Chenopodium album 180 Lettuce 27Amaranthus retroflexus 180 Swiss chard 24Urtica dioica 157Diplotaxis erucoides 145Diplotaxis tenuifolia 125

(V. Bianco, University of Bari)

Weeds are genetic resources

Vitamin C(mg/100 g f.w.)

Weeds must be managed

- cause yield losses

- cause quality losses

- cause technological costs

- are hosts for diseases and pests

Each of the effect depends on:speciesdensity of individualstime

IPM – ideals

- Cultural practices- Biological control

- Check weeds- Physical Options

- Herbicides

Common practice

- Herbicides

- Cultural practices

- Physical Options

No aspects of biologyor diversity

Current Weed Management

Future Weed Management ?

- Patch specific spraying- Sensor based mechanics - Robots - Fleets of robots

- Biological control - Conservation bio-control ?

Seeds Seedlings

Weed seed predation

- Ecosystem service - Missing link in population dynamics- Conservation bio-control

Diversity - a narrative in Integrated WeedManagement

- Diversity of cultivated crops and rotations

- Diversity of management

- Diversity of herbicide MoA

- Diversity of weeds?

Assume: The same number of weedy plants is built by

- Many species

- Few species

What is „better“? (thinking fast)

Assume: The same number of weedy plants is built by

- Many speciesMany criteria for herbicide choice

- Few speciesFew criteria for herbicide choice

Few species makes herbicides choice efficient

Weed control with herbicides is efficient

Diversity in weeds is effectiv

Long-term Systematic approach

Short-termInput-Output approach

Do the right things. Do the things right.

Intensification, herbicides, more MoA, more herbicides

Species losses

> 50

spe

cies

/ara

ble

site

< 5 species/arable site

Adapted biotypes in species

Humans breed crops - „Nature“ breeds weedsadapted to survive

~300

ara

ble

wee

d sp

ecie

s

Less crops, intensification, herbicides, more herbicides

Species losses

> 50

spe

cies

/ara

ble

site

< 5 species/arable site

Species

~300

ara

ble

wee

d sp

ecie

s

Many individuals Few individuals

Rationales for future weed management

Many species Many sensitive species - no adapted species

System Manage-

ment

ControlSeeds

Manage-ment

Diversity

manage-able

allow

Diversity

manage-able

allowResearch

and Develop-

ment

Manage-ment

Herbicides

Thanks to you for listening to my thoughts! Thanks to SLU växtskyddskonferens for inviting me.

Thanks to my group for sharing my thoughts!