Overview on Weed Management
Background Issues • Weeds
– Yield losses– Input efficiency – Input associated with control
• labor• chemical• energy
• Long-term effects– Restore soil productivity– Environment– Sustainability
• Increase in land use pressure
Goals of Cropping System Management
• Maintain or improve system productivity
• Minimize inputs
– labor, chemicals, energy
• Minimize environmental impact
– degradation of soil and water quality– impact on non-target organisms and
processes
•Green RevolutionGreen Revolution
•Selection for harvest indexSelection for harvest index
•Adoption on large scaleAdoption on large scale
Synergies –Synergies –
Varieties X Fertilizer X IrrigationVarieties X Fertilizer X Irrigation
HerbicidesHerbicides
•Herbicide resistanceHerbicide resistance
•Increased environmental concernsIncreased environmental concerns
•Low input efficiency and low profitLow input efficiency and low profit
Future trends in herbicide usageDull time
Star Perfomers
Significant weed problems
Storing up problems and paying the price
•New class of herbicidesNew class of herbicides
•Herbicide tolerant cropsHerbicide tolerant crops
•Spraying techniquesSpraying techniques
•New crop culture (direct seeded rice)New crop culture (direct seeded rice)
•Conservation agricultureConservation agriculture
•Climate changeClimate change
Crisis leading to opportunities
WEED SPECIES
IS THE NATURAL BIOLOGICAL UNIT TIED TOGETHER BY SHARING THE COMMON GENETIC POOL
QUANTITY OF FACTORS FOR WHICH THERE IS MINIMUM REQUIREMENT AFFECTS THEIR ASSOCIATION IN CROPPING SYSTEM
Ecological consideration in Weed Management
Understand how weeds invade
How weeds continue to exist inspite of good control measures
How the ecosystem functions
Introduce system approach in IWM
SURVIVAL STRATEGIES OF WEEDS
POPULATION BASED: RATE AT WHICH THE POPULATION WILL INCREASE WHERE THERE IS NO SHORTAGE OF RESOURCES
IT RELIES ON PRODUCTION OF LARGE NUMBER OF SEEDS. PHALARIS IN RICE- WHEAT ECOSYSTEM
STRONG EXPLOITIVE ABILITY: FEW REPRODUCTION UNITS . CANADA THISTLE
High fertilizer use will increase the weed flora in favour of grasses
Simplification of weed flora will lead to increase in herbicide use
Rainfed transplanted rice
Upper, medium and low toposequence Fimbristylis miliacea Cyperus iria Cynodon dactylon Paspalum distichum Cyperus difformis
• Why some technologies fly and some technologies flop
• E.g. Grass weed management in RW cropping system
• Herbicide resistance management
• Bed-planting in rice
• Bed-planting in sole crop compared to intercropped system
TIME OF SOWING
Dry Direct Seeded Rice (DSR)
Weed management
DSR
Timeliness of the control operation at early crop growth stages
Good control of the preceding crops
Crop yield losses up to 90% due to weed competition in poorly managed fields
Transplanted rice (TPR)
Weed management is conducted just before transplant
Rice has a significant size and competitive advantage over subsequently emerging weeds
Cultural methods
Stale seed bed-applying light irrigation and use of non-selective herbicides (53% control)
Good crop establishment
Surface mulch and cover crops-physical barrier to emerging weed
Sesbania co-culture (brown manuring at 25- 30 DAS with 2,4 D ester at 0.4-0.5 kg/ha) – can reduce about 50% weed without any averse effect on rice yield
Tillage systems-ZT 2-3 yrs reduce weed seed bank
Chemical control
Consideration
Individual herbicides have strength and also weekness e.g. Bispyriback
Rotational use with different modes of actions- inhibits herbicides tolerant or resistant weed biotypes
Proper spray techniques-control efficacy of herbicides e.g. flat fan nozzle in combination with multiple nozzle booms
Pre-emergence herbicides, apply when there is sufficient soil moisture
Pre-plant herbicidesGlyphosate (systematic) and Paraquat (contact)
Pre-emergence herbicides
Pendimethalin (1 kg a.i ha) within 3 DAS
Post-emergence herbicides
Bispyribac (Nominee gold) @ 25 g a.i./ha at 15-25 DAS (grassess, broadleaved and sedges) and 2,4 D @ 500 g/ha
Cyperus rotundus control
Post-emergence:1. Pyrazosulfuron (25-30 g ai/ha)
1. Halosulfuron (60 g ai/ha)2. Azimsulfuron (35 g ai/ha)3. Bispyribac (suppress) (30 g ai/ha)
Motha
Echinochloa spp./ Phalaris ( resistance)/ regeneration
Pre-emergence: 1. Pendimethalin (1.0 kg ai/ha)2. Oxadiargyl (90 g ai/ha)
Post-emergence:1. Bispyribac (25 g ai/ha)2. Bispyribac + oxadiargyl (20 g + 90 g ai/ha)3. Bispyribac + azimsulfuron (20 + 20 g ai/ha)
E. colona E. crus-galli
Shama Masta
Leptochloa & Eragrostis spp control
Pre-emergence: 1. Pendimethalin (1.0 kg ai/ha)2. Oxadiargyl (90 g ai/ha)
Post-emergence:1. Cyahalofop (120-150 g ai/ha)2. Azimsulfuron (35 g ai/ha)
Leptochloa chinensis
Ergrostis japonica
Leptochloa chinensis
Ergrostis japonica
Cyperus rotundus and Physalis
• Halosulfuron (60 g ai/ha)
• Azimsulfuron ????
PhysalisC.rotundus
Complex flora dominated by Cyperus
• Tank mixtures– Pyrazosulfuron + bispyribac– Halosulfuron + bispyribac– Bispyribac + azimsulfuron– WEEDY RICE– Herbicide resistant maize/ wheat / rice– Weed management in upland Kharif crops
Complex annual flora
• Oxadiargyl+ bispyribac• Pendimethalin + bispyribac• Azimsulfuron + bispyribac
• Shifting weed flora • Intercrop weed management
Weedy rice: Emerging problem in DSR
• Stale seedbed• Certified seed (free
from weedy rice seeds)• Removing panicles
before seed production• Hybrid rice
Cultivated rice weedy riceCultivated rice weedy rice
Weedy rice in rice fieldWeedy rice in rice field
New emerging problematic weeds
• Weedy rice
• Leptochloa
• Eragrostis
Leptochloa chinensis
Ergrostis japonica
Leptochloa chinensis
Ergrostis japonica
…however, poor application techniques result in poor control.
Uncontrolled phalaris resulting from poor
herbicide distribution
Real Time Delivery
• Application of research matters as much or more.
• Requirement: awareness of what farmers need and its opportunities.
• Facts: Experts in one technology find it hard to see the potential in another that may eventually displace it.
• Answer: Find ways for people working in outstations or even private sector to contribute to innovations.