Effectiveness of Herbicides

When herbicides are sprayed on soil or leaves, they are translocated through the xylem and phloem tissues to reach the active site and accumulate there.

After entering the plant body, herbicides disrupt various physiological and biochemical processes. For example — inhibiting photosynthesis, disrupting respiration and mitochondrial function, interfering with protein and nucleic acid metabolism, inhibiting seed germination, etc.

Details of Some Herbicides:

1. Paraquat Dichloride:
   It is a contact, non-selective herbicide. It controls grasses, sedges, and broad-leaved weeds.
   It is used before crop planting, in fallow lands, playgrounds, railway lines, and for controlling water hyacinth in wetlands.
   Dose: 24 S.L. 1–3 liters/acre.
2. Glyphosate:
   It is a translocated, non-selective herbicide. It controls grasses and broad-leaved weeds.
   Used before crop planting, in fallow lands, playgrounds, railway lines, and for controlling water hyacinth and other weeds in wetlands.
   Dose: 41% S.L. 800–2000 ml/acre.
3. Pendimethalin:
   It is a selective herbicide. Applied before weed emergence and before or within 2–3 days of crop planting.
   Controls grasses and broad-leaved weeds. Mainly used in pulses, potato, oilseeds, cotton, etc.
   Dose: 30 E.C. 1300–2600 ml/acre.
4. Pretilachlor:
   It is a selective pre-emergence herbicide. Controls grasses, sedges, and broad-leaved weeds.
   Mainly used in rice. Applied within 2–3 days of transplanting.
   Dose: 50% E.C. 400–800 ml/acre.
5. 2,4-D:
   It is a selective herbicide. Mainly kills broad-leaved weeds.
   Can be used in cereal crops, sugarcane, and fruit orchards. Applied before or after weed emergence.
   Dose: 80 W.P. 800–1200 ml/acre.
6. Metribuzin:
   It is a selective herbicide. Kills both grasses and broad-leaved weeds.
   Can be applied before or immediately after weed emergence. Used in wheat, maize, potato, tomato, soybean.
   Dose: 70% W.P. 150–500 grams/acre.
7. Metsulfuron Methyl + Chlorimuron Ethyl:
   It is a selective herbicide. Kills grasses and broad-leaved weeds.
   Applied after weed emergence. Used in rice, wheat and other cereal crops. In rice, spray when there is 1–2 cm of water in the field, 10–12 days after transplanting.
   Dose: 20% W.P. 8–10 grams/acre.
8. Oxadiazon:
   It is a selective herbicide. Kills grasses and broad-leaved weeds.
   Applied before or immediately after weed emergence. Used in rice.
   Dose: 80% W.P. 40–50 grams/acre.
9. Oxyfluorfen:
   It is a selective herbicide. Kills grasses and broad-leaved weeds.
   Applied before or immediately after weed emergence. Used in rice, potato, onion, groundnut.
   Dose: 23.5% E.C. 200–1000 ml/acre.
10. Pyrazosulfuron Ethyl:
    It is a selective herbicide. Kills grasses, sedges, and broad-leaved weeds.
    Used as pre-emergence, mainly within 2–3 days of rice transplanting and in seedbeds.
    Dose: 10% W.P. 50–60 grams/acre.
11. Ethoxysulfuron:
    It is a selective herbicide. Kills grasses and broad-leaved weeds.
    Applied immediately after weed emergence in rice.
    Dose: 15% W.D.G. 30–40 grams/acre.
12. Quizalofop Ethyl:
    It is a selective herbicide. Mainly kills grassy weeds.
    Applied after weed emergence. The field should have moisture. Used in jute, sesame, vegetables, soybean, mustard, potato.
    Dose: 5% E.C. 300–400 ml/acre.
13. Penoxsulam:
    It is a selective herbicide. Kills grasses, sedges, and broad-leaved weeds.
    Applied after weed emergence, mainly within 10–12 days of rice transplanting.
    Dose: 24% S.C. 37.5 ml/acre.
14. Cyhalofop Butyl:
    It is a selective herbicide. Mainly used to kill Shyama grass and Molanta grass in rice seedbeds.
    Applied after weed emergence, within 10–12 days of sowing in puddled rice seedbeds.
    Dose: 10% S.C. 600–1000 ml/acre.
15. Bispyribac Sodium:
    It is a selective herbicide. Kills grasses, sedges, and broad-leaved weeds.
    Applied after weed emergence, mainly 25–30 days after rice transplanting when weeds have 3–4 leaves.
    Dose: 10% E.C. 80–120 grams/acre.
16. Propaquizafop:
    It is a selective translocated herbicide. Mainly kills grassy weeds.
    Applied after weed emergence. Used to control grassy weeds in gram, mung, and soybean crops.
    Dose: 10% E.C. 200–400 ml/acre.
17. Imazethapyr:
    It is a selective herbicide. Kills grasses and broad-leaved weeds.
    Applied immediately after or after weed emergence. Mainly used in soybean and groundnut.
    Dose: 10% S.L. 400–500 ml/acre.
18. Sulfosulfuron:
    It is a selective translocated herbicide. Kills grasses and broad-leaved weeds.
    Applied after weed emergence. Mainly used in wheat to control Fela grass, Bathua, and wild methi.
    Dose: 75% W.P. 13–14 grams/acre.
19. Flucetosulfuron 10% WG:
    It is a selective translocated herbicide. Works both before and after weed emergence.
    It inhibits the activity of the acetolactate synthase enzyme.
    Dose: 100 grams/acre. Can be applied from 5 to 10–12 days after rice transplanting. Mainly used in rice. Controls grasses and broad-leaved weeds.

Weed Control in Different Crops:

1) Upland Broadcast Rice and SRI Method Rice:

The main weeds in rice fields are Shyama, Bindimutha, Jalmutha, Dadmari, Panpatari, Lobong, Shushuni, Kalmi, Helencha, Hanspana, Chhotopana, Jhanji, Kodai, etc.

• Oxyfluorfen 23.5% E.C. 400 ml/acre within 5 days of sowing — mainly kills grasses, sedges and broad-leaved weeds.
• Or Oxadiazon 25% E.C. 1600 ml/acre within 5 days of sowing.
• Or Pendimethalin 30 E.C. 1350 ml/acre within 5 days of sowing.
• Or Pyrazosulfuron Ethyl 10% W.P. 50–60 grams/acre within 2 days of sowing.
• Within 10–12 days of sowing: Ethoxysulfuron 15% W.D.G. 40 grams/acre for sedges and broad-leaved weeds.
• Or within 15 days of sowing: Metsulfuron Methyl + Chlorimuron Ethyl 20% W.D.G. 8 grams/acre.
• Or within 15 days of sowing: Penoxsulam 24% S.C. 37.5 ml/acre.

2) Weed Control in Transplanted Rice:

• Oxyfluorfen 23.5% E.C. 400 ml/acre within 5 days of transplanting.
• Or Oxadiazon 25% E.C. 1600 ml/acre within 5 days of transplanting.
• Or Pendimethalin 30% E.C. 1350 ml/acre within 5 days of transplanting.
• Or Pyrazosulfuron Ethyl 10% W.P. 50–60 grams/acre within 2–5 days of transplanting.
• Within 10–12 days of transplanting: Ethoxysulfuron 15% W.D.G. 40 grams/acre.
• Or within 15 days: Metsulfuron Methyl + Chlorimuron Ethyl 20% W.D.G. 8 grams/acre.
• Or within 15 days: Penoxsulam 24% S.C. 37.5 ml/acre.
• Within 20–25 days of transplanting: Bispyribac Sodium 10% E.C. 80–120 ml/acre.

Note: 200–250 liters of water per acre is required. Recently, Flucetosulfuron 10% WG has come to the market. It destroys weed enzyme activity. Dose: 100 grams/acre. Can be applied from 5 to 12 days after transplanting.

3) Weed Control in Wheat Fields:

Main weeds in wheat are Bathua, Mutha, Krishnanil, Senji, Wild Pea, Hatka, Wild Oat, Fela grass, Durba, Shyama, etc.

• Metribuzin 70% W.P. 450 grams/acre within 30–35 days of sowing for grasses, sedges and broad-leaved weeds.
• Or Oxyfluorfen 23.5% E.C. 400 ml/acre soon after sowing.
• Or Sulfosulfuron 75% W.D.G. 13 grams/acre for grasses and broad-leaved weeds within 10–12 days of sowing.
• Or Isoproturon 75% W.P. 500 grams/acre within 10–20 days of sowing for grassy weeds.
• Or Metsulfuron Methyl 20% W.P. 10 grams/acre within 25–30 days of sowing for broad-leaved weeds.

Note: The field should have sufficient moisture. 200–250 liters of water per acre is required. For Fela, Wild Oat and other grasses: Clodinafop Propargyl 15% W.P. 100–150 grams/acre or Fenoxaprop P Ethyl 10% E.C. 400 ml/acre within 2–3 days of sowing.

4) Weed Control in Potato:

The main weeds in potato fields are — Bathua, Mutha, Krishnanil, Senji, Hatka, Durba, Shyama, Wild Spinach, Wild Brinjal, Punarnava, Muktjhuri, etc.

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Weed Control in Potato (Continued):

Grasses, sedges, and broad-leaved weeds are controlled by applying Metribuzin 70% W.P. 450 grams/acre within 5–15 days of potato planting. In this case, sufficient moisture must be present in the soil.
Alternatively, Pendimethalin 30% E.C. 1350 ml/acre within 2–3 days of planting is mainly used to control grasses and broad-leaved weeds.
Or Fluchloralin 45% E.C. 600 ml/acre within 2–3 days of planting is mainly used to control grasses and broad-leaved weeds.
Or Trifluralin 48% E.C. 600 ml/acre immediately after land preparation is mainly used to control grasses, sedges, and broad-leaved weeds.

5. Weed Control in Mustard:

The main weeds of mustard are — Bathua, Mutha, Krishnanil, Senji, Hatka, Durba, Shyama, Panpalang, Wild Brinjal, Punarnava, Shiyal Kanta, Wild Chilli, Wild Methi, Shuaghas, Muktjhuri, etc.

• Fluchloralin 45% E.C. 1000 ml/acre before sowing seeds is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1350 ml/acre within 2–3 days of sowing is mainly used to control grasses and broad-leaved weeds.
• Or Isoproturon 75% W.P. can be used 25–30 days after sowing at 400 grams/acre to control grassy weeds.

6. Weed Control in Sesame:

The main weeds of sesame are — Mutha, Durba, Shyama, Wild Brinjal, Wild Chilli, Shuaghas, Kalmi, Keshut, etc.

• Fluchloralin 45% E.C. 900 ml/acre within 2–3 days of sowing is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1350 ml/acre within 2–3 days of sowing is mainly used to control grasses and broad-leaved weeds.
• Or for grassy weed control, Quizalofop Ethyl 5% E.C. 300–400 ml/acre can be used 30 days after sowing.

7. Weed Control in Groundnut (Chinese Peanut):

Weeds are almost similar to sesame.

• Fluchloralin 45% E.C. 1200 ml/acre before sowing seeds is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1350 ml/acre within 2–3 days of sowing is mainly used to control grasses and broad-leaved weeds.
• Or Oxyfluorfen 23.5% E.C. 150–200 ml/acre is used before or after weed emergence to control grasses and broad-leaved weeds.
• Or Imazethapyr 10% S.L. 400 ml/acre is used before or after weed emergence to control grasses and broad-leaved weeds.

8. Weed Control in Onion:

The main weeds of onion are — Mutha, Durba, Note, Bathua, Shyama, Bontepary, Dudhiya, Senji, etc.

• Fluchloralin 45% E.C. 900 ml/acre 7–10 days before transplanting seedlings is mainly used to control grasses and broad-leaved weeds.
• Or Oxyfluorfen 23.5% E.C. 200–250 ml/acre within 4–5 days of transplanting is used before or after weed emergence to control grasses and broad-leaved weeds.
• Or Oxadiazon 25% E.C. 2400 ml/acre within 1–2 days of transplanting is used to control grasses and broad-leaved weeds.

9. Weed Control in Pulse Crops:

The main weeds of pulse crops are — Mutha, Bathua, Durba, Shuaghas, Hurhure, Krishnanil, Wild Spinach, Shiyal Kanta, Senji, Shyama grass, Hetka, etc.

(ক) Lentil (Masoor):

• Fluchloralin 45% E.C. 900 ml/acre before sowing seeds is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1000 ml/acre within 2–3 days of sowing is mainly used to control grasses and broad-leaved weeds.

(খ) Gram (Kala):

• Fluchloralin 45% E.C. 900 ml/acre before sowing seeds is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1000 ml/acre within 2–3 days of sowing is mainly used to control grasses and broad-leaved weeds.
• Or Propaquizafop 10% E.C. 300–400 ml/acre can be used within 25–30 days of sowing mainly to control various types of grassy weeds.

10. Cauliflower / Cabbage:

The main weeds are — Mutha, Bathua, Durba, Shuaghas, Hurhure, Krishnanil, Wild Spinach, Shiyal Kanta, Senji, Shyama grass, Hetka, etc.

• Fluchloralin 45% E.C. 900 ml/acre 7–10 days before transplanting seedlings is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1000 ml/acre within 2–3 days of transplanting is mainly used to control grasses and broad-leaved weeds.
• Or Alachlor 50% E.C. 800 ml/acre within 2–3 days of transplanting is mainly used to control grasses and broad-leaved weeds.

11. Weed Control in Jute:

The main weeds of jute are — Durba, Mutha, Kodai, Dudhiya, Bontepary, Wild Jute, Latamari, Taraghas, Bindimutha, Keshut, Note, Punarnava, etc.

• Fluchloralin 45% E.C. 1250 ml/acre 1–2 days before sowing seeds is mainly used to control grasses and broad-leaved weeds.
• Or Pendimethalin 30% E.C. 1500 ml/acre within 2–3 days of sowing seeds is mainly used to control grasses and broad-leaved weeds.

Additionally:

• Quizalofop Ethyl 5% E.C. 300 ml/acre 15–20 days after sowing is mainly used to control grassy weeds.
• Or Fenoxaprop P Butyl 12.5% E.C. 1000 ml/acre 15–20 days after sowing is mainly used to control grasses and broad-leaved weeds.

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