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 – Varieties X Fertilizer X Irrigation  Herbicides Varieties X Fertilizer X Irrigation  Herbicides Herbicide resistanceHerbicide resistance Increased environmental concernsIncreased environmental concerns Low input efficiency and low profitLow input efficiency and low profit Future trends in herbicide usage Dull 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 DAS with 2,4 D ester at 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 herbicides Glyphosate (systematic) and Paraquat (contact)  Pre-emergence herbicides Pendimethalin (1 kg a.i ha) within 3 DAS  Post-emergence herbicides Bispyribac (Nominee 25 g a.i./ha at DAS (grassess, broadleaved and sedges) and 2,4 500 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 ( g ai/ha) E. colonaE. crus-galli ShamaMasta

Leptochloa & Eragrostis spp control Pre-emergence: 1. Pendimethalin (1.0 kg ai/ha) 2. Oxadiargyl (90 g ai/ha) Post-emergence: 1. Cyahalofop ( g ai/ha) 2. Azimsulfuron (35 g ai/ha) Leptochloachinensis Ergrostisjaponica Leptochloachinensis Ergrostisjaponica

Cyperus rotundus and Physalis Halosulfuron (60 g ai/ha) Azimsulfuron ???? Physalis C.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 rice Cultivated rice weedy rice Weedy rice in rice field

New emerging problematic weeds Weedy rice Leptochloa Eragrostis

…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.