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!