Rice

Weed Management

Common weeds in rice fields are grouped into three categories

• Grasses
• Sedges
• Broad leaved weeds

Grasses

Grasses are the monocots with two ranked leaves, that are usually long, narrow and upright with parallel venation

• Cynodon dactylon
• Echinochloa colonum
• Echinochloa crussgalli
• Dactyloctenium aegyptiacum
• Setaria glauca
• Digitaria longifolia
• Saccharum munja
• Eleusine indica
• Eragrostis interupta
• Paspalum scrobiculatum
• Leersia hexandra
• Eragrostis aspera

Sedges

Sedges are very similar to grasses but have three ranged leaves.

• Cyperus rotundus
• Cyperus iria
• Cyperus difformis
• Fimbristylis milliaceae
• Scirpus erectus
• Cyperus haspan

Broad leaved weeds

Broad leaved weeds are usually dicots with tap root system.

• Eclipta alba
• Aegetarum conyzoides
• Monochoria vaginalis
• Ludwigia parviflora
• Commelina benghalensis
• Sphenoclea zeylanica
• Marsilea quadrifolia
• Mollago pentaphylla
• Eichornia crassipes
• Salvinia molesta
• Alternanthera sessilis
• Ammanea baccifera
• Astercantha longifolia

Weed Management

Nursery

• Apply any one of the pre-emergence herbicides viz., Pretilachlor + safener 0.3kg/ha, on 3rd or 4th day after sowing to control weeds in the lowland nursery.
• Keep thin film of water
• Avoid drainage of water, this will control germinating seeds

Transplanted rice

Pre-emergence

Use any one of the following as pre-emergence application per hectare:

• Butachlor – 2.5 lit.
• Thiobencarb 2.5 lit.
• Fluchloralin 1 lit.
• Pendimehtalin 3 lit.
• Anilophos 1.25 lit.

Alternatively, use any one of the following pre-emergence herbicide mixture viz.,

• Thiobencarb 1.2 + 2.4 DEE 1.5 lit.
• Butachlor 1.2 + 2.4 DEE 1.5 lit.
• Fluchloralin 1.0 + 2,4 DEE 1.5 lit.
• Pendimethalin 1.5 + 2,4 DEE 1.5 lit.re per hectare or
• Anilophos + 2,4 DEE ready mix at 1.25 lit.re per hectare followed by one hand weeding on 30-35th day after transplanting will have a broad spectrum of weed control.
• Any herbicide should be mixed with 50kg of sand and applied uniformly in the field over 2.5 cm water on the 10th day without draining for 2 days.
• Herbicides can be applied along with neem coated urea in heavy weed infested area.

Post emergence

Apply 2,4-D sodium salt (Fernoxone 80% WP) 1250g in 625 lit. of water with high volume sprayer after three weeks or when the weeds are in 3-4 leaf stage.

Cultural practices

• Adopting dual cropping of rice-azolla, and rice-green manure reduces the weed infestation to a greater extent.
• Summer ploughing and cultivation of irrigated dry crops during post-rainy periods reduces the weed infestation.
• If pre-emergence weedicides are not used hand weed on 15th day after planting.
• Rotary weeder can be used at 10 days interval from 15 DAT. It is a labour saving practice also aerates the soil and root zone, prolongs the root activity, and improves the grain filling through efficient translocation.

Cono weeder

• A manually operated mechanical weeder called Cono weeder is now available for weeding between rows of paddy crop.
• The cono weeder has two conical rotors mounted in tandem with opposite orientation. Smooth and serrated blades mounted alternately on the rotor uproot and burry weeds because the rotors create a back and forth movement in the top 3 cm of soil, the cono weeder can satisfactorily weed in a single forward pass without a push pull movement.
• The Cost of the unit Rs. 900/-It is easy to operate by a single operator and it does not sink in puddled soil
• Field capacity is 0.18 ha/day.

Biological Control

Certain insects and microbes feed on weeds contributing to the weed control.