There are many kinds of weeds in the rice paddy field and the varieties are also different in different areas of China. The most common and harmful weeds are Barnyard grass, then Cyperus difformis L., Monochoria vaginalis, Monochoria vaginalis, chinese sprangletop, leptochloa chinensis and potamogeton tepperi A.Benn.
Usually there will be the first emergence peak of the weeds in around 10 days after sowing, transplanting and throwing. The weeds in this period are mainly annual weeds including grass weeds like barnyard grass, leptochloa chinensis and nutsedge like cyperus difformis L.. They occurs very early with huge quantity and heavy harm.
The second emergence peak of the weeds will appear in around 20 days after sowing, transplanting and throwing. The weeds mainly are nutsedge and broad-leaf weeds.
Generally, from south to the north, from hot areas to cold areas, the weeds’ community structure tends to more simple and the symbiotic period of rice and weeds obviously shorten.
Below we will introduce those weeds:
1: Double cropping rice area(southern China)
Main weeds are barnyard grass, flatstalk bulrush, monochoria vaginalis, cyperus difformis L., potamogeton tepperi A.Benn., sagittaria trifolia Linn., sagittaria pygmaea miq., marsilea quadrifolia, Rotala rotundifolia(Buch- H am)Koehne, ludwigia adscendens, ludwigia hyssopifolia, Ludwigia prostrata, fimbristylis miliacea (L.) Vahl, leersia hexandra swartz.
2: Double cropping rice area(eastern, middle China)
Main weeds are barnyard grass, Monochoria vaginalis, Cyperus difformis L., Flatstalk Bulrush, Scirpus juncoides Roxb, Rotala indica (Willd.) Koehne, Eclipta prostrata, Leptochloa chinensis, ndernia procumbens, Alisma plantago-aquatica Linn., Potamogeton tepperi A.Benn., Alligator Alternanthera, Paspalum distichum L., Ammannia baccifera L, etc.
3: Single cropping rice(north eastern China)
Main weeds are barnyard grass, Potamogeton tepperi A.Benn., Scirpus juncoides Roxb, tstalk Bulrush, Sagittaria trifolia Linn., Alisma plantago-aquatica Linn., Bidens tripartita L., Najas minor All., Monochoria korsakowii, Lindernia crustacea (L.) F. Muell, Scirpus validus Vahl , etc.
4: Single-cropping rice area(northwest China)
Main weeds are barnyard grass, Flatstalk Bulrush, cyperus iria, Potamogeton tepperi A.Benn., Najas minor All., Alisma plantago-aquatica Linn., Reed, cattail, Spirogyra, Alisma gramineum, charophyte, etc.
5: Single-cropping rice area(southwest plateau)
Main weeds are barnyard grass, Eleocharis yokoscensis, Cyperus difformis L., Potamogeton tepperi A.Benn., Lindernia procumbens, Sagittaria Pygmaea Miq., Monochoria vaginalis, Najas minor All., Scirpus triqueter Linn., wild water chestnut, serotinus, Ammannia auriculata, etc.
The weeds’ occurring and action differ in different cultivation methods and the control methods also differ too much. So, before killing the weeds, should make sure the cultivation methods:
1: Seedling Transplanting paddy rice field
2: Direct sowing seeds paddy rice field
3: Seedling throwing paddy rice field
4: Upland rice field
The rice herbicides can be divided as: Herbicides for Seedling transplanting field, Herbicides for Seedling throwing field and Herbicides for Direct sowing seeds field. In the actual application, we mainly choose the high-safety herbicides considering the rice’s age. The Direct sowing seeds field has the highest requirement for herbicides’ safety and the Seedling transplanting field has the lowest requirement.
So the herbicides for Direct sowing seeds field can be used in other 2 kinds of the fields; But the herbicides for the other 2 kinds of fields can’t be used in Direct sowing seeds field or may cause phytotoxicity; And the herbicides for Seedling transplanting field can’t be used in Seedling throwing field and the Herbicides for Seedling throwing field can be used in Seedling transplanting field.
Prevention for the phytotoxicity:
1: To apply herbicides reasonably;
2: More instructions from the government and the sellers;
3: Combine the herbicides’ characteristics with the local climate, soil condition, etc.
Common rice herbicides’ characteristics
Usually there will be the first emergence peak of the weeds in around 10 days after sowing, transplanting and throwing. The weeds in this period are mainly annual weeds including grass weeds like barnyard grass, leptochloa chinensis and nutsedge like cyperus difformis L.. They occurs very early with huge quantity and heavy harm.
The second emergence peak of the weeds will appear in around 20 days after sowing, transplanting and throwing. The weeds mainly are nutsedge and broad-leaf weeds.
Generally, from south to the north, from hot areas to cold areas, the weeds’ community structure tends to more simple and the symbiotic period of rice and weeds obviously shorten.
Below we will introduce those weeds:
1: Double cropping rice area(southern China)
Main weeds are barnyard grass, flatstalk bulrush, monochoria vaginalis, cyperus difformis L., potamogeton tepperi A.Benn., sagittaria trifolia Linn., sagittaria pygmaea miq., marsilea quadrifolia, Rotala rotundifolia(Buch- H am)Koehne, ludwigia adscendens, ludwigia hyssopifolia, Ludwigia prostrata, fimbristylis miliacea (L.) Vahl, leersia hexandra swartz.
2: Double cropping rice area(eastern, middle China)
Main weeds are barnyard grass, Monochoria vaginalis, Cyperus difformis L., Flatstalk Bulrush, Scirpus juncoides Roxb, Rotala indica (Willd.) Koehne, Eclipta prostrata, Leptochloa chinensis, ndernia procumbens, Alisma plantago-aquatica Linn., Potamogeton tepperi A.Benn., Alligator Alternanthera, Paspalum distichum L., Ammannia baccifera L, etc.
3: Single cropping rice(north eastern China)
Main weeds are barnyard grass, Potamogeton tepperi A.Benn., Scirpus juncoides Roxb, tstalk Bulrush, Sagittaria trifolia Linn., Alisma plantago-aquatica Linn., Bidens tripartita L., Najas minor All., Monochoria korsakowii, Lindernia crustacea (L.) F. Muell, Scirpus validus Vahl , etc.
4: Single-cropping rice area(northwest China)
Main weeds are barnyard grass, Flatstalk Bulrush, cyperus iria, Potamogeton tepperi A.Benn., Najas minor All., Alisma plantago-aquatica Linn., Reed, cattail, Spirogyra, Alisma gramineum, charophyte, etc.
5: Single-cropping rice area(southwest plateau)
Main weeds are barnyard grass, Eleocharis yokoscensis, Cyperus difformis L., Potamogeton tepperi A.Benn., Lindernia procumbens, Sagittaria Pygmaea Miq., Monochoria vaginalis, Najas minor All., Scirpus triqueter Linn., wild water chestnut, serotinus, Ammannia auriculata, etc.
The weeds’ occurring and action differ in different cultivation methods and the control methods also differ too much. So, before killing the weeds, should make sure the cultivation methods:
1: Seedling Transplanting paddy rice field
2: Direct sowing seeds paddy rice field
3: Seedling throwing paddy rice field
4: Upland rice field
The rice herbicides can be divided as: Herbicides for Seedling transplanting field, Herbicides for Seedling throwing field and Herbicides for Direct sowing seeds field. In the actual application, we mainly choose the high-safety herbicides considering the rice’s age. The Direct sowing seeds field has the highest requirement for herbicides’ safety and the Seedling transplanting field has the lowest requirement.
So the herbicides for Direct sowing seeds field can be used in other 2 kinds of the fields; But the herbicides for the other 2 kinds of fields can’t be used in Direct sowing seeds field or may cause phytotoxicity; And the herbicides for Seedling transplanting field can’t be used in Seedling throwing field and the Herbicides for Seedling throwing field can be used in Seedling transplanting field.
Prevention for the phytotoxicity:
1: To apply herbicides reasonably;
2: More instructions from the government and the sellers;
3: Combine the herbicides’ characteristics with the local climate, soil condition, etc.
Common rice herbicides’ characteristics
| Phenoxyacetic Acid Herbicides | 2,4-D | Broad leaf weeds(no effect for grass weeds) | 2,4-D butyl ester’s volatilization amount is huge in high temperature and easy to separate to harm the nearby Dicotyledon crops and the trees | When the temperature is between 20-28℃, the efficiency rise following with the temperature’s rising. But if under 20℃, the efficiency will decrease |
| MCPA | Broad leaf weeds(no effect for grass weeds) | For gramineous plants, they are sensitive in the seedling period. The resistance rise in 3-4 leaves and reach the highest in the late tillering period. In young panicle differentiation stage , they become sensitive again. The efficiency is obviously poor under 18℃, and is poor for the weeds that are still under the earth | In around 15 days after the rice seedling transplanting, apply MCPA 20% AS 200-250ml/mu with water 50Kg, can control most nutsedge and broad-leaf weeds | |
| Dinitroaniline herbicide | Pendimethalin | Grass weeds and part of the broad-leaf weeds | For upland rice | Use before the emergence |
| Acetanilide herbicides | Metolachlor | Annual grass weeds and part of the small seeds broad-leaf weeds | Highest safety | |
| Butachlor | Annual grass weeds and part of the broad-leaf weeds | |||
| Propanil | Good efficiency product for the control of barnyard grass. Also can be used to kill other grass weeds and Dicotyledon weeds like Monochoria vaginalis, crab grass, setaria viridis, etc.. | Easy to meet phytotoxicity if the temperature is higher than 30℃ | ||
| Mefenacet | Good efficiency product for barnyard grass | Selective systemic action, in 5-7 days after the seedling transplanting and the rice turns green, 1.5 leaves of barnyard grass. | ||
| Diphenylethers herbicides | Oxyfluorfen | Control broad-leaf weeds, nutsedge and barnyard grass | Poor safety | Before emergence or early stage after emergence |
| Fluoroglycofen | Broad-leaf weeds | Post-emergence, contact toxicity, should work with sunshine. So has to be applied in sunny days. | ||
| Sulfonylurea herbicides | Tribenuron-Methyl | Broad-leaf weeds | ||
| Bensulfuron-methyl | For broad-leaf weeds and nutsedge, poor efficiency for grass weeds | Only has good efficiency for the weeds within 2 leaves | Can be applied after sowing, but before 2 leaves stage of the weeds | |
| Pyrazosulfuron-ethyl | Broad-leaf weeds, nutsedge | Can’t be used in the emergence stage of the late paddy rice. Or may cause phytotoxicity | Usually use in 1-3 leaves stage of the paddy rice. | |
| Penoxsulam | Good efficiency for barnyard grass(including the resistant barnyard grass to Propanil, Quinclorac), annual nutsedge and kinds of broad-leaf weeds | Can mix with Cyhalofop-butyl | Early stage after the emergence(direct sowing seeds rice paddy field) | |
| Heterocyclic herbicides | Bentazone | Broad-leaf weeds and nutsedge | Mainly work as Contact toxicity | In around 20-30 days after seedling transplanting, 30-40 days after seeds direct sowing, 3-5 leaves of the weeds. |
| Quinolinic acids | Quinclorac | Barnyard grass | Can mix with Propanil, Cyhalofop-butyl, Bensulfuron methyl, Pyrazosulfuron-ethyl, etc. | Can use in 1-7 leaves stage of barnyard grass |
| Benzoic acid herbicide | Bispyribac-sodium | Barnyard grass and other grass weeds, also control most broad-leaf weeds and some nutsedge | Good efficiency for old barnyard grass and Paspalum distichum L.. Can kill the barnyard grass in 1-7 leaves stage. | Can be used after rice’s emergence and before its earing up. Best efficiency in 3-5 leaves stage of barnyard grass |
| Sulfonyolurea herbicides | Cyhalofop-butyl | Grass weeds | From its absorption to weeds’ death need 1-3 weeks. May rise antagonism if mix with other broad-leaf weeds herbicides | Selective for paddy rice field, can only use as stem&leaf treatment |
| Metamifop | Annual grass weeds | Mist sprayer is forbidden. The water used per MU should be no less than 30Kg. Use alone and cann’t mix with other agrochemicals or adjuvants. | Seedling transplanting rice, Direct seeds sowing rice | |
| Triazolinone herbicides | Carfentrazone-ethyl | Broad-leaf weeds and nutsedge | Good activity for the weeds that are resistant to the 对sulfonylurea herbicide |
Mix with MCPA and use in middle-late tillering stage of the paddy rice
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