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.